Hyphenation with Numbers and Units of Measure
The Blue Book of Grammar and Punctuation
Hyphenation with Numbers and Units of Measure
Few punctuation marks prompt as much debate and discussion about when and where to place them as the hyphen does.
Opinions and directives vary. GrammarBook.com aims to help define common written English that applies proper, generally accepted rules. Those guidelines likewise look to reinforce a precise and articulate use of the language.
This means our guidance for our current hyphen topic may differ from the recommendations you may find in research and scientific stylebooks.
An issue that still challenges many writers concerns the use and placement of hyphens with numbers and units of measure. For example, which of the following are correct?
50-ft. yacht
80 lb. bag
six centimeter caterpillar
100-meter dash
In addressing this topic, we side closer to the 16th edition of The Chicago Manual of Style. CMOS’s stance can be a bit confusing at times; we hope to clarify it in this article.
According to CMOS, “if an abbreviation or a symbol is used for the unit of measure, the quantity is always expressed by a numeral. Such usage is standard in mathematical, statistical, technical, or scientific text, where physical quantities and units of time are expressed in numerals, whether whole numbers or fractions, and almost always followed by an abbreviated form of the unit … Note that hyphens are never used between the numeral and the abbreviation or symbol, even when they are in adjectival form.”
Correct:
50 ft. yacht
80 lb. bag
6 cm caterpillar
100 m dash (Note that CMOS uses a period when abbreviating English units but not when abbreviating metric units.)
CMOS further advises using a hyphen when the unit, abbreviation, or symbol is spelled out, with the exception of percent.
Correct:
50-foot yacht
80-pound bag
six-centimeter caterpillar (Note that we spelled the number here because it’s less than ten and not used with a symbol or abbreviation.)
100-meter dash
But
10 percent raise
Written English in specialized fields such as healthcare, education, and science often adheres to its own specific stylebook. In those cases, the stylebook should serve as the writer’s guiding authority.
Pop Quiz
Correct the following sentences if needed. The answers appear below.
1. She served the drinks in 16 ounce mugs.
2. She served the drinks in 16-oz mugs.
3. The mugs could hold up to 16-ounces.
4. Weather predictions are about 50-percent accurate.
5. The 621-gram diamond is the largest in the world.
6. The 621-g. diamond is the largest in the world.
Pop Quiz Answers
1. She served the drinks in 16-ounce mugs. [use a hyphen when the unit is spelled out]
2. She served the drinks in 16 oz. mugs. [Hyphens are never used between the numeral and abbreviation, even when in adjectival form. Use a period when abbreviating English units.]
3. The mugs could hold up to 16 ounces. [no hyphen as “16 ounces” is not used as an adjective here]
4. Weather predictions are about 50 percent accurate. [hyphens are not used with percent]
5. The 621-gram diamond is the largest in the world. CORRECT
6. The 621 g diamond is the largest in the world. [Hyphens are never used between the numeral and abbreviation, even when in adjectival form. A period is not used when abbreviating metric units.]
If the article or the existing discussions do not address a thought or question you have on the subject, please use the "Comment" box at the bottom of this page.
Magnificent, I will apply this to my writings.
We are pleased to hear that this article was helpful for you. Thank you for writing.
This is very helpful for developing my writing skills in my college classes. Thank you so much for all this information.
I saw your section on hyphens. I cannot recast the following. I was wondering whether it was punctuated correctly. I didn’t use suspended hyphens. Thank you very much.
a 15%-to-20%-a-year reduction in profits
a 20%-a-year reduction
a 20%-per-year reduction
a 15-to-20-percent-a-year reduction in profits
a $2-million-to-$5-million-a-year baseball contract
a $5-million-a-year contract
a $35,000-to-$45,000-per-year position
Correctly to all punctuation above with the hyphenage?
Thank you very, very much.
We recommend that you write:
a 15% to 20% per year reduction in profits (we recommend using the more formal “per year” over “a year,” the latter being a term that is sometimes associated with only one year) OR
a 15%–20% per year reduction in profits (Note that we have used an en dash to be consistent with most publishers when designating a range. You may also use a hyphen: a $1-$5 per day surcharge.)
a 20% per year reduction
a 15 to 20 percent per year reduction in profits
a $2 million to $5 million per year baseball contract OR
a $2 million–$5 million per year baseball contract
a $5 million per year contract
a $35,000 to $45,000 per year position OR
a $35,000–$45,000 per year position
Without recasting the examples below, are they very technically correctly punctuated with the hyphens as I have them?
a $1-to-$5-a-day surcharge
a $10-to-$20-per-barrel price
an $80-million-to-$90-million-a-year industry
a 10-to-15-percent-a-year increase
a 10%-to-15%-a-year increase
65-to-85-cent-a-week raises
a group of 20-to-30-year-old men
Deepest thanks.
We recommend that you write:
a $1 to $5 per day surcharge (we recommend using the more formal “per day” over “a day,” the latter being a term that is sometimes associated with only one day) OR
a $1–$5 per day surcharge (Note that we have used an en dash to be consistent with most publishers when designating a range. You may also use a hyphen: a $1-$5 per day surcharge.)
a $10 to $20 per barrel price OR a $10–$20 per barrel price
an $80 million to $90 million per year industry OR an $80 million–$90 million per year industry
a 10 to 15 percent per year increase
a 10% to 15% per year increase OR a 10%–15% per year increase
65- to 85-cent per week raises
a group of 20- to 30-year-old men (note the use of the suspended hyphen in these final two examples)
Isn’t this example flawed in terms of punctuation?
65- to 85-cent per week raises
Shouldn’t it be
65- to 85-cent-per-week raises
Thank you.
There is no universal agreement among the leading reference books on
how to handle this situation. We believe that the meaning is conveyed
clearly either way.
I believe that with the examples below I don’t need to use commas between any of the elements (in all examples) because the numerals stand out and the examples are crystal clear without them. Do you concur with the punctuation in Set 1?
SET 1
a 2-hour 11-minute 42-second finish time
a 2-hour 11-minute and 42-second finish time
a 3-year 9-month 17-day project
…lasted 3 years 9 months 17 days.
…lasted 3 years 9 months and 17 days.
But if we spell them out, I believe we need commas for clarity:
SET 2
a two-hour, eleven-minute, forty-two-second finish time
…lasted two hours, eleven minutes, and forty-two seconds.
While we were not able to find specific guidance on this situation in The Chicago Manual of Style, we do note that The Associated Press Stylebook (AP) would use commas and would express the times in numerals. For clarity, we recommend using commas whether the times are expressed in numerals or spelled out. For sports statistics, AP recommends: a finish time of 2:11:42.
But if I opted to use ‘a year’ instead of ‘per year,’ would it still be treated the same, minus the hyphens? Good, technically speaking, to all below?
an $80 million to $90 million a year industry
an $80 million–$90 million a year industry
an $11 a barrel price
an $11 per barrel price
a $10–$15 per barrel price
a $10–$15 a barrel price
a $2 million to $4 million per quarter loss
a $2 million–$4 million per quarter loss
a $5 million per quarter loss
a $5 million a quarter loss
In followup to our response of February 25, 2017, we strongly recommend that “per” be favored over “a” in these constructions in order to ensure clarity and avoid miscommunication. Per is the cleaner word by definition. A phrase such as a $5 million a quarter loss lacks clarity to us, especially in such a weighty matter as whether $5 million is being lost each quarter or in a specific quarter. If you insist in using “a,” we recommend using hyphens in these constructions to assist in clearer reading and cleaner copy:
an $80 million to $90 million-a-year industry
an $80 million–$90 million-a-year industry
an $11-a-barrel price
a $10–$15-a-barrel price
a $5 million-a-quarter loss.
Can we drop the word ‘million’ after the first number?
Instead of:
‘an $80 million–$90 million per year industry,’
Could we tighten it up and use
‘an $80–$90 million per year industry’?
Writing an $80-$90 million per year industry is too open to misinterpretation. While perhaps unlikely in this particular case, this type of construction in general could be misinterpreted as an industry ranging from 80 dollars to 90 million dollars. The AP Stylebook specifically recommends the form “$80 million to $90 million.”
Is it better to write “..who is 80+ years,…” or “..who is over 80-years old…”
Is there ever a time when using “+” is applicable?
We do not recommend using the mathematical plus sign in that manner in formal writing. You could write either “who is 80-plus years old” or “who is over 80 years old.” The phrase “who is over 80 years old” does not use a hyphen. Please see our post Hyphens with Numbers for more information.
I got the correct answer for “There are one thousand four hundred twenty pages in the book.”
However, contrary to what grammar books say about it, I still think
“There are one-thousand four-hundred twenty pages in the book.” is better.
Can you give a reason (other than “grammar books say so”) why my preference is undesirable?
As described in our post Numbers as Adjectives, you would hyphenate when a number is used with another word to form a compound adjective before a noun, that is, when they describe another object. An example would be “a one-thousand-four-hundred-twenty-page book.” In your example sentence, the numbers one thousand and four hundred are numbers that are not hyphenated. All compound numbers from twenty-one through ninety-nine are hyphenated. Also see our Rules for Writing Numbers.
Instead of using suspended hyphenation, would you concur that the examples below are correct with respect to using both one en-dash and hyphens within the same phrase?
Examples:
20–30-foot boards
a 50–100-mile radius
25–35-year-old men
10–15, 25–35, and 40–45-milligram tablets
$45 million–$55 million-a-year business
(No hyphen after $45 and $55; correct?)
$250,000–$300,000 per year business
We find your use of both an en dash and hyphens to be creative and acceptable to us. However, we are unable to find this sort of usage in any of our usual reference books such as the Chicago Manual of Style or the Associated Press Style Book. If you locate anything further on this topic, please send it along to us.
What about fractions?
I have a technical guide that has:
Using (3) 2 1/2-in. screws per corner, construct a 4 ft. x 8 ft. frame.
(12) 2-1/2 in. Wood Screws
As the post states, hyphens are never used between the numeral and the abbreviation. Also, the fraction 2 1/2 does not contain a hyphen, and we see no reason to capitalize “wood screws.” This method of writing “(3) 2 1/2” and “(12) 2 1/2” is efficient for saving space. Therefore, we recommend the following:
Using (3) 2 1/2 in. screws per corner, construct a 4 ft. x 8 ft. frame.
(12) 2 1/2 in. wood screws
or, if space allows:
Using three 2 1/2 in. screws per corner, construct a 4 ft. x 8 ft. frame.
Twelve 2 1/2 in. wood screws
Street No.-5 or Street No.5 which is correct way of writing ?
Because you have not provided any context or a specific sentence, our best guess is either Street No. 5 or street No. 5.
What about when using fractions? Would it be correct to say:
7 1/2-inch molding
1/2-inch to 5/8-inch thick
Also, which could be correct: 400-Amp electrical service or 400 A electrical service?
Your two fractions are written correctly. Because amp is a type of abbreviation for ampere, we recommend writing “400 amp (or 400 A or 400-ampere) electrical service.”
I am having a discussion with a doctor. We submit lab samples and dictate how they are submitted. Is either example more correct than the other? See below:
Sections are submitted labeled (A1-A2).
Sections are submitted labeled (A1 & A2).
The major style manuals advise that the ampersand should not replace the word and, except in widely accepted abbreviations. See our post & What About the Ampersand? The parentheses are unnecessary here. Since it appears you have only two labels, write “Sections are submitted labeled A1 and A2.”
If you would like to be more specific, you could write:
“Two sections are submitted labeled A1 and A2.”
“Five sections are submitted labeled A1-A5.”
I am having an argument on units of measurement. (see below) which is correct? 60-inches or 60 inches?
My assumption is when you are describing a specific measurement it is hyphenated but when you are describing how many inches it is not.
Which is right?
NPS 1/2: Maximum span, 60-inches; minimum rod, 1/4-inch. OR
NPS 1/2: Maximum span, 60 inches; minimum rod, 1/4-inch
Following the guidance of The Chicago Manual of Style, measurements are only hyphenated when used as adjectives, and even then only according to how the units of measurement are expressed. For example:
The pipe span is 60 inches.
The pipe covers a 60-inch span.
The pipe covers a 60 in. span.
Please let me know if this is acceptable (if not correct):
Wells are constructed of 2- or 4-inch-diameter, Schedule 40, polyvinyl chloride (PVC) casing with 0.010-inch, factory-slotted screen installed between 10 and 25 feet below ground surface (bgs).
(There’s a lot there, I know.)
I am a geologist who writes and reviews technical reports, and I work with people who tell me, “It just doesn’t look right,” so I very much appreciate being able to show them your posts. Thank you!
Your hyphens look fine to us; however, we would cut back on commas:
Wells are constructed of 2- or 4-inch-diameter Schedule 40 polyvinyl chloride (PVC) casing with 0.010-inch factory-slotted screen installed between 10 and 25 feet below ground surface (bgs).
Would it be proper to write “Write a 300- to 400-word essay,” or should I use some other method? Is this way to convey a range ok?
Your hyphenated phrase is written correctly.
I am an engineer not a writer and I have received four different answers from four different people who should know what they are doing. However, I am now more confused that when I started. What is the correct way to write a bullet list of a quantity of a sized element?
I am writing a cookbook and need a consistent way to list ingredients. My question is about the hyphen, where does it go? Is it better to write this list some other way?
for example:
1 med. head lettuce
1 cup celery
½ cup green onions, finely chopped
1-8 oz. can water chestnuts
1-10 oz. package frozen green peas
2 cups mayonnaise
2 tsp. sugar
Is this written properly or is there a better way?
There is no specific rule about how this is to be written. We recommend:
One 8 oz. can water chestnuts OR (1) 8 oz. can water chestnuts
One 10 oz. package frozen green peas OR (1) 10 oz. package frozen green peas
Should I use 3-bottle bundle or 3 bottle bundle when I am referring to my products?
The style guides recommend spelling out the number three; therefore, we prefer “three-bottle bundle.” See our post Numbers: Words or Numerals.
I was wondering which was correct:
We provide “million-dollar-marketing”
We provide “million-dollar marketing”
We provide “million dollar marketing” (which is how it currently reads)
Isn’t “million dollar” modifying “marketing” ? (and should my question mark be inside or outside the quotation marks lol!)
“Million-dollar marketing” is correct for the reason you stated. A period belongs inside the closing quotation marks: We provide “million-dollar marketing.” See our post Numbers as Adjectives for more information. Our Rule 5a of Question Marks says, “The placement of question marks with quotation marks follows logic. If a question is within the quoted material, a question mark should be placed inside the quotation marks.” Therefore, the question mark goes outside the quotation marks with no space before it: Isn’t “million dollar” modifying “marketing”?
Thank you! Helped me justify comment while doing a peer review to a manuscript that used way too many hyphens.
I’m trying to determine the correct way to write a height or length that includes both feet and inches. For example, which of these would be correct:
The dress hung on my five-foot-three frame.
or
The dress hung on my five-foot three frame.
or
The dress hung on my five foot three frame.
The dress hung on my five-foot-three frame. OR
The dress hung on my five-foot-three-inch frame.
For a phrase representing a range of values, should the abbreviated unit appear after both numbers or only after the last number?
For example
… which is between 15 to 20 g.
or
… which is between 15 g to 20 g.
We talk more about this topic in Staying on Target with Ranges. There you will see that proper grammatical phrasing is either “between … and” or “from … to.” Thus we recommend … between 15 and 20 g. Repeating the abbreviation for grams is not necessary. You may also use an en dash for this purpose: … between 15–20 g.
I am using “one-part alcohol in three-parts water” in a sentence.
Is this correct?
The numbers one and three are not part of compound adjectives in your example. Therefore, write “one part alcohol in three parts water.”
With regards to science journal articles, do I need to repeat the unit of measure when using (1) to/from and (2) En dash?
(1) “Diamonds principally form at great pressures from 4.5 to 6.5 GPa.” Do I need to repeat the unit GPa after the 4.5 as well?
(2) “Diamonds principally form at great temperatures, 950 – 1350 °C.” Do I need to repeat the degree unit after the 950 as well? And should there be a hyphen or En dash between the numbers in (2) and what about spaces?
The Chicago Manual of Style recommends repeating the symbol if it is closed up to the number in a range. The °C symbol is typically closed up (950°C) while GPa (4.5 GPa) is spaced from the number. Therefore, you were correct to write 4.5 to 6.5 GPa, but you should write 950°C–1,350°C. We typically recommend inserting a comma in numbers of four or more digits, but you may follow the standard in your field. Simply be consistent.
Further, in regard to consistency, CMOS recommends the en dash for number ranges, while The Associated Press Stylebook uses only hyphens. Again, choose one style and be consistent.
We do have additional guidance in our blog post Writing Dates and Times. There we provide more information in regard to the proper use of the pairs from-to and between-and.
I type court transcripts, and recently a speaker said, “It’s 22 or -3 pages long.”
A proofreader insists it should read, “It’s 22 or 3 pages long.”
I disagree because the speaker isn’t suggesting it might be 3 pages long, but rather 23 pages long.
Comments? References? All help appreciated!
We suggest writing “It’s twenty-two or -three pages long.”
Otherwise, “It’s 22 or 3 pages long” could also be clear from the context.
Which is correct:
The film is projected on an 80-feet wide by 60-feet high screen.
The film is projected on an 80-ft. wide by 60-ft. high screen.
The film is projected on an 80-ft wide by 60-ft high screen.
Is a hyphen necessary between feet/ft./ft and wide/high?
The words wide and high are part of the compound adjectives describing screen. Therefore, they are included in the hyphenated terms. However, as the post states, “Note that hyphens are never used between the numeral and the abbreviation or symbol, even when they are in adjectival form.” Therefore, we recommend hyphenating numbers and units of measure as adjectives when the units are written out but omitting hyphens with abbreviations.
The film is projected on an 80-foot-wide by 60-foot-high screen. OR
The film is projected on an 80 ft. wide by 60 ft. high screen.
…280 degree view of the surrounding mountains.
OR
…280-degree view of the surrounding mountains.
Since 280-degree is used as a compound adjective in front of the noun view, it should be hyphenated. See our post Hyphens with Numbers for more information.
Should any hyphens be used when writing “Less than or equal to 15”?
More specifically, what if it is the title of a book, song, etc., e.g. “Less Than or Equal To 15”?
No hyphens would be needed in “less than or equal to 15” as either a phrase or a song title (“Less Than or Equal to 15”).
What about when talking about multiplication/size difference?
1. (object a) is 15-thousand times more massive than (object b)
2. (object a) is 15,000 ✕ more massive than (object b).
3. (object a) is fifteen-thousand times more massive than (object b).
4. object a) is 15,000 times more massive than (object b).
There are no hyphens required. See our Rules for Writing Numbers and our post Numbers as Adjectives.
Object a is fifteen thousand times more massive than object b. OR
Object a is 15,000 times more massive than object b.
Which is correct: (0-10 scale) or (0-10 Scale)? Thank you so much.
We see no reason to capitalize the word scale.
Which would be correct in narrative? “I bought a twelve-pack and drank all but one.” Or, “I bought a 12-pack and drank all but one.”
Our post Numbers: Words or Numerals? explains that America’s two most influential style and usage guides have different approaches. The Associated Press Stylebook recommends spelling out the numbers zero through nine and using numerals thereafter, and The Chicago Manual of Style recommends spelling out the numbers zero through one hundred and using figures thereafter. Therefore, it is up to the writer to choose a style.
Which is correct?
The tree measures 3 feet tall. or
The tree measures 3-feet tall.
No hyphen is necessary; however, our post Numbers: Words or Numerals? explains that the major influential style guides recommend writing out “three” instead of using a numeral. Therefore, we recommend “The tree measures three feet tall.”
I am trying to figure out how to correctly use hyphens for “an 8-foot, 2-inch span.” (I have to use numerals.) How did I do?
We recommend writing “an 8-foot-2-inch span.”
How should hyphens be used when a term is being introduced/used for the first time in a research article and hence an abbreviation is given directly after the full term? For example, if you have a “Knowledge Graph-based product” but want to introduce the abbreviation (KG) after Knowledge Graph, should it be “Knowledge Graph (KG)-based product”?
Many thanks in advance!
You could write “Knowledge Graph (KG)–based product.” Your other option would be to identify the meaning of the abbreviation KG early in the article, thereafter using the term “KG-based product.” Note also that “Knowledge Graph” is a compound modifier of “based”; as such, it would be punctuated with an en dash.
Great information. Thank you! More casual question here… I am printing a recipe for JELL-O shots as a gift for a 21st birthday… Is a hyphen recommended anywhere for “shot glass size plastic cups”:
Place shot-glass size plastic cups on a baking sheet.
or
Place shot glass-size plastic cups on a baking sheet.
or
Place shot-glass-size plastic cups on a baking sheet.
or
Place shot glass size plastic cups on a baking sheet.
Thank you in advance.
Our Rule 1a of Hyphens says, “Generally, hyphenate two or more words when they come before a noun they modify and act as a single idea. This is called a compound adjective.” Therefore, the following is grammatically correct:
Place shot-glass-size plastic cups on a baking sheet.
Another approach is to punctuate an open compound in a compound modifier with an en dash:
Place shot glass–size plastic cups on a baking sheet.
Do I understand well that the thousands separator is usually omitted when the measurement becomes part of an adjective? For instance, in the case of “a line of 1,600 feet” / “a 1600-foot line”? Or should the thousands separator remain: “a 1,600-foot line”?
Thank you so much in advance for your advice!
We are not familar with any rule omitting the comma when using a hyphenated term. We recommend writing “a 1,600-foot line.”