Americans use the old British Imperial measuring system of feet and inches for linear distances. Even a number of Canadian firms do. Most scientific research (and most construction outside of North America) uses the metric system of meters and centimetres. Converting between the two is simple arithmetic, but very important. NASA contractors caused the Mars Explorer mission to fail because one used feet and inches, the other metric.
Take the number of feet in the item being measured and multiply by 12, to get inches.
Add any additional inches to the result of Step 1. For example, 5 feet, 5 inches is 5 x 12 = 60, plus 5 = 65 inches.
Multiply the inches by 2.54 to get centimetres. For the example above, 65 x 2.54 = 165.1 centimetres.
Divide centimetres by 100 to get meters. The 165.1 centimetres above is 1.651 meters.
You can make a quick approximation by multiplying feet by 30 to get centimetres, and treating one meter as one yard and four inches. One square meter is almost exactly 1550 square inches, or (for round-number approximations) 11 square feet.