How do you convert 250 square mm to square meters?

There are 1000 mm in 1 m, so there are 10002 square mm in 1 square meter. 1000*1000=1,000,000 so there are 1,000,000 square mm in 1 square meter. Divide 250 by 1,000,000 and you get 1/4000, or 0.00025, so 250 square mm=.00025 square m. Basically, divide the number of sq. mm by 1,000,000.