Verified answer

0.000188 mm^2

Unit Converter

http://www.unitconversion.org/area/square-millimet...

The SI prefixes for size go down in multiples of 1000. So a millimetre is 1/1000th of a metre, and micrometre is 1/1000th of a millimetre, a nanometre is 1/1000th of a micrometre, and so on.

Remember that the SI prefixes are for linear units. The issue becomes more complicated when you're talking about areas and volumes.

Think about the relationship between centimtres and metres for a moment. One centimetre is 1/100th of a metre. However, because a square metre is 100cm along each side, one square metre is 10,000 square centimtres, and a cubic metre (which is 100x100x100cm) is 1,000,000 cubic centimetres.

Now, I sort of regret bringing in centimetres which are multiples of 100 instead of 1000 like in the SI prefixes, but I always feel it's a bit easier to get a grip on the slightly smaller numbers. But anyway - where the difference between metres and millimetres is 1/1000th, the difference between square metres and square millimetres is 1/1,000,000th. So to move up one set of units from square micrometres to square millimetres, you need to divide by a million (move the decimal point six places to the left). Which, as the commenter below points out, gives you 0.000188.