# Correct way to say “km^2”

How do we say km2 in words? Do we use km exponent by two, square kilometer, kilometer squared or something else?

• Another "or something" pronunciation is 'hectohectares'. – James Waldby - jwpat7 Oct 12 '11 at 18:03
• but, please, the equivalent in imperial units, "square feet", is sq. ft., not ft² – nohat Oct 12 '11 at 22:51

When talking about it as in a formula, you would say "kilometer squared". You would typically use "square kilometer" when discussing area, as in "his farm was three square kilometers".

• As I use the terms, "square kilometers" and "kilometers squared" are different units. 10 square kilometers is a square with an area equal to 10 times the area of a block 1 kilometer on each side. 10 kilometers squared is a block 10 kilometers on each side, thus 100 square kilometers in area. I parse them as `10 (square kilometers)` and `(10 kilometers) squared`. – David Schwartz Oct 12 '11 at 20:01
• @David: Wouldn't you normally just say 10 by 10 kilometers for the latter? – Cerberus_Reinstate_Monica Oct 12 '11 at 20:21
• I believe that people say "kilometers squared" when reading off a formula or a value because this word order matches the order of the characters on the page, which means they don't need to "read ahead" to see the 2 before saying "kilometer" as they read the formula from left to right. I've never heard of "kilometers squared" meaning anything different from "square kilometers". – Ryan C. Thompson Oct 12 '11 at 21:21
• @scottishwildcat: I agree. I did some googling and couldn't fine any evidence that anyone actually uses it. (And to Cerberus: Not if it wasn't 10 by 10 kilometers. It means of equivalent area to such a square. The idea is to avoid large and confusing numbers, primarily with non-metric units that don't have prefixes.) – David Schwartz Oct 13 '11 at 10:49
• @David: I have always understood a block 10 kilometres on each side to be "10 kilometres square", not squared. Reading "km^2" as "kilometres squared" is not uncommon (though this perhaps doesn't make it right, and in careful speech I would say "square kilometres"). – Billy Oct 13 '11 at 22:03

Depends on the context.
If you are referring to an area then square kilometres is correct - but if it's a scientific unit that happens to be in length^2 then kilometres-squared.

edit: Checked the SI recommendations.

Although in general you would say kilomtres-squared when reading a formula, they recommend that if the length^2 represents an area eg. Pressure = N/m^2, then you read it as newtons-per-square-metre, since it is the area of a real square metre. I can't off-hand think of any units that are length^2 where it isn't an area.

However if the unit has a different quantity squared, such as Acceleration = m/s^2 then you read it as per-second-squared since a square second has no meaning on it's own.

Square kilometers (or kilometres).

The correct terms when written in a formal context are:

kilometres squared

or

square kilometres

Remember these are different.

Three kilometres squared is three kilometres on one side and three kilometres on the other side which is 9 square kilometres.

Three square kilometres is three kilometres on one side and one kilometre on the other side.

In a formulaic context 3 kilometres squared is written

3Km x 3Km

And 3 square kilometres is written like this

3Km2

with the two being an exponent (supertext).

• `Three kilometers squared` would be `(3 [km])^2` which in turn will become `(3 [km])^2 = 3 [km] * 3 [km] = 9 [km^2]`. To make it less confusing you should treat units seperate from the values. – Spoike Nov 3 '11 at 11:36

Am I alone in saying "km²" as "kay-emm squared"?

• Lonely Izkata... – GEdgar Oct 13 '11 at 0:08
• Would upvoting this answer mean agreeing ("Yes you are alone") or "No, I say that too"? :-) – ShreevatsaR Oct 13 '11 at 1:53
• @ShreevatsaR: I'm fine with either wink wink nudge nudge =^_^= – Izkata Oct 13 '11 at 2:24

'3 kilometres squared' means, for me, a square of side 3km, but to others it means 3 square kilometres. The official terminology is square kilometres, not kilometres squared, but since there is no agreement on its meaning better not use the expression 'kilometres squared', but, if it's what you mean, say square kilometres instead, or, as mentioned above 'key-emm squared'. If you mean a square of side 3km then say that, which I think is a pity.

• "3 kilometers square" is a square of side 3 kilometers, which has an area of 9 square kilometers. But the question is about the notation km^2, which is either "kilometers squared" -- the unit "pascal" (N/km^2), is expressed as newtons per kilometers squared -- or "square kilometers" -- A pascal is 1 newton per square kilometer. – deadrat Aug 26 '15 at 9:35