When it comes to measuring the area of parcels of land — outdoor spaces such as farms and forests — one of the most popular units to measure with is an acre. But what does that mean for its plural form, “acres”?
It is correct to say acres. The noun “acre” is a unit of measurement, which means that it’s a countable noun that accepts an -s in the plural form. When referring to a fraction or a single whole, an acre is correct. When referring to anything larger than 1.0 acre, acres is correct.
Here, we’ll look at the different ways that we talk about an acre and how these same rules apply to units of measure in general.
Is It “Acre” or “Acres”?
Acre is correct when referring to anything equal to or less than an acre. Acres is correct when referring to anything greater than 1.0 acre. When you’re referring to the size or area of a piece of land, a common unit to use is the acre. And, just as with most units of measure, it can be a singular or plural noun. “Acre” can also be part of a hyphenated adjective in some cases.
Let’s take a look at the singular, plural, and hyphenated adjective forms of the word “acre.” You’ll be using this word correctly in every situation!
Is It Grammatically Correct to Say “Acres”?
Yes, it is grammatically correct to say “acres” when you are referring to more than one acre. The word “acre” is a regular, countable noun, which means that you can make the plural form by simply adding -s to the end. That means the plural of “acre” is “acres.”
If you’re using the word “acre” after a number, you need to make it plural. For instance, if you’re describing the size of a three-acre farm to a friend, you should say, “It’s three acres.” You can’t say “It’s three acre” because you need to use the plural form “acres” after the number.
For more about tricky singular and plural forms, check out our article “Food vs. Foods: What’s the Difference?”
What About the Decimal or Fraction Form?
If you’re using a decimal form of a number with “acre,” you should use the plural form. It takes singular form with a fraction if it is less than or equal to one and the plural form if it is more than one (source). Let’s take a look at these examples:
Your orchard is only half an acre. I’m surprised that you harvested so many peaches!
In this example, the fraction “half” describes how many acres. Since “half” is less than one, we use the singular form in this case.
We dedicated 0.68 acres to growing flowers near the house.
Here, we use the plural form of “acre, ” with the decimal,” even though the value is less than one.
It’s a small house, but it sits on 3.5 (three and a half) acres of land.
In this example, you are using a decimal to refer to a plot of land that is more than one acre large. So, you need to use the plural form, “acres.”
A Hyphen Makes an Adjective
Of course, the rules are a bit different if you’re using “acre” as part of a hyphenated adjective. Usually, such an adjective will look like “number-acre,” followed by the noun it describes. A popular example is the “Hundred-Acre Forest,” where Winnie the Pooh likes to play.
If you’re using the word “acre” in a hyphenated adjective, you don’t need to use the plural form. Instead, you should use the singular form after the hyphen, even if the number before the hyphen is greater than one.
Let’s have a look at this exception in action:
Mia inherited a 50-acre farm from her grandfather, but she doesn’t know what to do with it.
In this example, the word “50-acre” is one adjective that describes the noun “farm.” Since it is one word, and because it has that hyphen, you have to use the singular form, “acre,” in constructing the adjective.
For more about hyphenated adjectives, check out our article, “Long-Term or Long Term: Is It an Open, Hyphenated, or Closed Compound?”
What Does “Acre” Mean?
The word “acre” refers to the size of an area. It is a unit of measure, so every acre is the same size as every other acre, just as every liter is the same volume as every other liter, and every pound is the same weight as every other pound.
One acre is the same as 4,046.86 square meters or 43,560 square feet or 4,840 square yards (4047 square meters) of land (source).
How Do You Use “Acres”?
You can use “acres” to express how big an area is. Generally, this area should be outdoors, and it usually describes a parcel of land with clear boundaries.
When Can You Use “Acres”?
You can use “acre” to describe an area of land with clear boundaries. Basically, if you want to know how much land lies between some specific demarcation points, you can describe the answer in terms of acres.
In What Context Can You Use “Acres”?
Usually, we use the word “acres” to describe land, an outdoor space, or a natural space, like a farm or a forest. However, if you want to express the size of an indoor space, you should use “square feet” or “square meters.”
Using “Acres” in a Full Sentence
Here are some examples of different ways that you can use the words “acre” and “acres” in a full sentence:
- The park was more than 1,000 acres, so it was impossible to explore it all.
- An acre of land in the city costs a lot more than an acre of land in the countryside.
- How many acres of the farm did you dedicate to growing wheat?
- This 60-acre plot belonged to my mother’s family; it’s our family farm.
When Not to Use “Acres”
If you’re referring to an indoor space, like a gallery or home, you shouldn’t use “acres.”
As a general rule, we use “acre” to refer to the area of an outdoor space, like a wooded area or a prairie. So let’s take a look at the proper units of measure to use instead of “acres.”
If you are talking about an indoor space — that is, a space with a roof over it — then you don’t want to use “acres” to describe that area.
What Can You Use Instead of “Acres”?
Instead of “acres,” you can use “square feet” or “square yards” with the imperial system, or you can use “square meters” with the metric system. You can also use “square kilometers” in the metric system or “square miles” in the imperial system for an especially large space.
General Rules for Units of Measure
There are a few grammatical rules that apply whenever you’re speaking or writing about units of measure — whether you’re measuring time, space, volume, or weight. Let’s review them here and check out a few examples along the way.
Singular or Plural?
When referring to any unit of measure, it’s important to remember that each unit is a countable noun. This means that if you mention more than one unit, you have to use the plural form of the unit of measure.
This rule applies no matter what you’re measuring! Even if you’re using a unit of measure to count off something that you can’t see or touch — such as time or your score on your last English exam — you should use the singular form for one and the plural form for more than one.
If you’re using the unit of measure with a fraction, the same general rule applies — use the singular form with numbers going up to and including one, and then use the plural form with any number greater than one.
If you’re using a decimal form of a number with the unit of measure, then you should use the plural form.
Of course, not all units of measure are regular nouns, so be careful to check out the plural forms below!
| SINGULAR | PLURAL | ADJECTIVE |
|---|---|---|
| This door won’t move an inch! I can’t open it. | Please shift the picture a few inches to the left. Perfect! | I need a two-inch nail to hang this painting. |
| Could you please buy a liter of milk on your way home? | Could you please buy three liters of milk on your way home? | This is a two-liter bottle of milk. |
| The recipe calls for half a tablespoon of black pepper. | We need to add one and a half tablespoons of salt. | Please give the quarter-tablespoon measuring cup. |
Should I Capitalize the Unit of Measure?
Usually, when you’re using a unit of measure, it isn’t necessary to capitalize it. Of course, if it comes at the beginning of a sentence or is part of a proper name, then you should capitalize it.
So, if you’re using the unit of measure as a normal word in the middle of your sentence, there is no need to capitalize it. However, there are some exceptions to capitalization when abbreviating units of measure. Just be sure to double-check the abbreviation in those cases.
What About Abbreviations?
Most units of measure have an abbreviated version so that you don’t have to write out the whole word every time. There are three main patterns for the abbreviated form of a unit of measure (source):
Your first option is to take the first and last letter of the complete word. For instance, “quart” becomes “qt.,” “foot” becomes “ft.,” and “yard” becomes “yd.”
Another way is to use the first letter or two letters of the complete word. For example, “mile” becomes “mi.,” “inch” becomes “in.,” and “meter” becomes “m.” This method is very popular in the metric system; almost all metric units are abbreviated with the first letter of the complete word.
Or, if the complete unit of measure is more than one word, or if it includes a prefix, make the abbreviation by taking the first letter of each word and/or prefix. In this case, “miles per hour” becomes “mph,” “centimeter” becomes “cm,” and “miligram” becomes “mg.”
When you use the abbreviated form of the unit of measure, you don’t need to make it plural! There is no need to add that -s” at the end with the abbreviation. Instead, the abbreviation stands for both the singular and the plural form of the unit of measure.
Abbreviations Examples
Here are some of the most popular abbreviations; use this list as a handy guide when you’re reading texts with lots of units of measure.
Here are the most popular abbreviations for units of measure that refer to height, depth, and length:
- ft – foot/feet
- fm – fathom
- in – inch/inches
- mm – millimeter/millimeters
- cm – centimeter/centimeters
- m – meter/meters
These are some of the common abbreviations for units of measure that apply to area:
- ac – acre
- sq mi/mi² – square mile
- sq yd/yd² – square yard
- sq ft/ft² – square foot
- sq in/in² – square inch
- cm² – square centimeter
- m² – square meter
- km² – square kilometer
These are some of the most popular ways to abbreviate the units of measure for volume and capacity; you probably recognize these from the kitchen:
- tsp or t – teaspoon/teaspoons
- tbs, tbsp or T – tablespoon/tablespoons –
- c – cup/cups
- qt – quart/quarts
- ml – milliliter/milliliters
- l – liter/liters
- pt – pint/pints
- gal – gallon/gallons
Here are a few abbreviations that tell us about the temperature and energy:
- F – degrees Fahrenheit
- C – degrees centigrade/Celsius
- cal – calorie (small calorie)
- Cal – kilocalorie (large calorie, sometimes called “Kcal”)
This article was written for strategiesforparents.com.
Finally, these are the most common abbreviations that help us measure speed:
- mph – miles per hour
- kph – kilometers per hour
- kn – knots. Nautical miles per hour
Final Thoughts
When it comes to talking about the size of a parcel of land, the main imperial unit of measure is the acre. If you’re talking about more than one acre of land, then you need to use the plural form, “acres.”
There’s one exception, though: if you have a hyphenated adjective that includes a number and the word “acre,” as in “The Hundred-Acre Forest,” then you shouldn’t use the plural form of “acre.” instead, just keep the singular form after the hyphen.
These rules apply whenever you’re using units of measure: use the plural form after any number greater than one, and use the singular form in the adjective construct after the number and the hyphen.