# Using "of" with numbers

I am confused about using "of" with numbers. When do numbers come before or after the "of"?

After the "of"

A bill of £42.50

A height of 10 metres

A weight of 225 kilograms

Before the "of"

2 kilograms of apples

Millions of insects

12-mile stretch of fine sand

So, I wonder which of the following examples are true ?

1- 5 inch screen

2- 5 inch of screen

3- A screen of 5 inch

1'- 2 kilograms dumbbell

2'- 2 kilograms of dumbbell

3'- A dumbbell of 2 kilograms

Some of your examples are valid but they would be used in different contexts. Also, some need to be plural and others singular.

Television and computer screens are measured diagonally. A 5 inch screen would measure 5 inches from the bottom left corner to the top right corner.

When we use a number ahead of a measure, we keep the measure singular. For example, a 10-kilometre run, a 20-pound weight, a 5-litre can.

Another way to say a 5-inch screen would be a screen of 5 inches. In this case it has to be plural - not 5 inch.

Someone who needed to mend a hole in a mosquito screen might require five inches of screen to cover the hole. To be precise, that would be either 5 square inches or, more likely, 5 inches square. Again, note the plural inches.

A dumbbell weighing 2kg is a 2 kilogram dumbbell. (Kilogram used in the singular here is a noun adjunct, acting as an adjective, like the examples above.)

If you were delivering a dumbbell in parts to somebody's door, you might say I have 2 kilograms of dumbbell for you - although this is an unusual way of putting it.

And a 2kg dumbbell can be described as a dumbbell of 2 kilograms although most people would simply call it a 2 kilogram dumbbell.

It's a matter of context.

• Thanks, one more question : Should I say "2-kilogram dumbbell" or "2 kilogram dumbbell" ? Are both okay ? Mar 5, 2019 at 16:23
• "When we use a number ahead of a measure, we keep the measure singular. For example, a 10-kilometre run, a 20-pound weight, a 5-litre can." Can we use this rule with plural nouns ? For example : "500-page books" or "5-litre cans" Mar 5, 2019 at 17:11
• Yes, the same rule applies to plural nouns - 200 kilogram lions. Measures are generally abbreviated after numbers. (abbreviations.yourdictionary.com/articles/…). When using the measure fully written, I should not use a hyphen, just a space. Where abbreviations are concerned, I have seen variations such as 20km, 20-km and 20 km. This may be a matter of style rather than of any rule. Others may be able to give you better guidance here. Mar 5, 2019 at 18:02

With countable nouns in the plural and with uncountable nouns, we use:

• X measure (in the plural) of Y

e.g. 2 kilograms of apples / 2 liters of water

With countable nouns in the singular, we can use:

• (a) X-measure (in the singular) Y

or

• (a) Y of X measure (in the plural)

e.g. a five-inch screen / a screen of five inches

• If I want to convert "books over 500 pages" to this form which one would be correct ? "500 pages of books"(that sounds wrong to me) or "500-page books" Mar 5, 2019 at 17:05
• You can say "books of (over) 500 pages" or "500-page books". Mar 5, 2019 at 19:58
• Thanks :) lastly I am allowed to use this form "2-kilogram apples" Mar 5, 2019 at 20:41
• No. Pay attention to the letters X and Y I used. X stands for a number, and Y for the thing being measured. You should say "2 kilograms of apples". "2-kilogram apples" would mean "apples each weighing 2 Kg"! Mar 5, 2019 at 20:46