Twelve inches make one foot. This calculator combines feet, inches and fractions into total inches, performs the selected operation, and converts the result into the units you need.
How the calculator works
Calculations use JavaScript floating-point numbers in total inches. The feet-and-inches reading and tape are rounded to the selected 1/2 through 1/32 inch. Decimal and metric outputs use the unrounded calculation, but their displayed digits are also rounded; they are not unlimited-precision exact values.
One inch is defined as exactly 0.0254 meters (2.54 centimeters). Conversion factors are exact, while floating-point calculations and displayed decimal values have finite precision. Divide total inches by 12 to obtain decimal feet.
Inputs and what they mean
Blank components in a partly filled measurement count as zero; an entirely blank row is not a measurement. Enter 0 explicitly for zero. Subtraction uses the first row minus every following row, so enter the starting measurement in the first row. Feet and inches are signed components: -5 feet plus 6 inches equals -54 inches; the fraction follows the sign of the combined feet and inches. For example, -2 feet, 6 inches and 1/2 gives -18.5 inches. Use a negative decimal value in reverse conversion for a negative whole measurement.
Read the rounded feet-and-inches result beside the decimal and metric conversions. The tape shows the rounded fraction, not a physical full-size ruler. Copy and CSV use the selected result; Share includes the active calculation.
Limits and edge cases
Division by zero and invalid or out-of-range values have no result. Correct the indicated field before using output actions. A third of an inch cannot be represented exactly by a tape fraction; choose a finer increment for a closer reading. Always use actual measured dimensions and verify safety-critical work against project specifications.
Nominal lumber sizes are product names, not measured dimensions. A typical finished 2×4 measures 1-1/2 inches by 3-1/2 inches. Use actual dimensions and account for measurement and rounding tolerances.