This calculator requires the use of Javascript enabled and capable browsers. This calculator is designed to give the result of a math calculation to verify that a foundation (or room, truss foundation, or other 90 degree structure) is actually square and correct in layout. (Be square or Repair...) The calculation is based on the Pythagorean Theorem. Reduced to simple construction terms, it says that the foundation length squared plus the foundation width squared equals the foundation diagonal distance (opposite corner to opposite corner) squared. It is also known in the construction industry as 3-4-5, meaning the if the length is 3 (squared = 9) and the width is 4 (squared = 16) then the diagonal is 5 (squared = 25). Verification is true in that 9 plus 16 is 25, of which the square root is 5. While protractors and T-Squares are very useful, the longer the distance for the measurement, the more accurate it is. (If you don't want to actually measure but can determine by a sting, both diagonals must be equal for a squared foundation.) Just a fraction of a degree deviation from 90 degrees, over 20 feet or more, is a substantial error in causing walls to not be straight or square. A little extra effort in the initial stages yields a much more professional structure in the end.

This calculator is capable of use in the American system of feet and inches, and the metric system of meters. Select the American or Metric number system first. In the feet and inches mode (American system), enter your value of feet indicated as Feet, then the inches, if there are any, in the box indicated as Inches. If you have a fraction of an inch, you may enter it. Keep in mind that this is a decimal fraction; for example .5 is 1/2 inch and .75 is 3/4 inch. If you are uncertain as to the conversion, you may use our conversion tables for precision up to 64ths of an inch in decimal. (If you already know the conversion of inches to a decimal, you may just enter it as feet. For example, you could enter 5 feet 6 inches as 5 in the feet box and 6 in the inches box, or just 5.5 in the feet box and no entry in the inches box.) In the metric mode, only the first box on length and width is used; the system and calculator accept decimals. The answer is returned in feet, inches and construction fractions (to 64ths) in the American mode while the Metric mode returns meters and decimal values. If you do more than one calculation, be sure to click on the Clear Values button between attempts.