Feet-Inch-Fraction Calculator
Between architects and civil engineers your plans are a mix of feet, inches, and fractions. Decimal feet are easier for computers and use in civil engineering, but field crews learned to measure with fractions. And, 99.9% of tape measures in the US are in inches and 1/16ths.
This calculator will help you add, subtract and multiply feet-inches-sixteenths, with imperial decimal and metric conversions alongside every result. It will even convert decimal feet (civil units) to feet-inch-fraction to match the tape measure on your belt.
Add or subtract two measurements directly. Multiply a dimension by a quantity. Divide a run into equal spans. The convert mode runs both directions: enter a metric or decimal value and get the fraction equivalent, or enter a feet-inch-fraction and see decimal feet, decimal inches, meters, centimeters, and millimeters all at once.
More on how the feet-inch-fraction calculator tool works below....
How this Calculator Works
Fractions round to the nearest 1/16 inch. For metric conversions, multiplied dimensions, or divided measurements, the rounding residual in the results shows the exact gap between the rounded fraction and the true value. For add and subtract of clean sixteenth-inch values, the residual is always zero.
Useful when a supplier spec is in millimeters and your field crew works in fractions, or when you are spot-checking a machine control elevation against a plan dimension.
Machine control systems from Trimble, Topcon, Leica, and Carlson store design elevations as decimal feet because that's what is used in civil construction. This tool translates those values to the format your crew reads.
Common Questions About Conversions
How do I add two measurements in feet and inches?
Select Add, then enter each measurement in the Feet, Inches, and Fraction fields. Fractions go down to 1/16 inch. The result appears automatically as feet-inches-sixteenths with decimal feet and metric equivalents below.
How do I convert feet and inches to meters or millimeters?
Select Convert and enter your feet-inch-fraction measurement in the lower input group. Use the unit dropdown next to the decimal field to switch between meters, centimeters, millimeters, and decimal inches. The decimal value updates automatically when you change your fraction input.
How do I convert a metric or decimal dimension to feet and inches?
Select Convert and enter your value in the top input field. Choose the unit from the dropdown. The feet-inches-fraction equivalent populates in the fields below. The conversion uses 1 ft = 0.3048 m exactly and rounds to the nearest 1/16 inch.
What is the rounding residual?
Fractions display to the nearest 1/16 inch. When the exact result does not land on a 1/16 increment, which is common with metric conversions and multiplied or divided measurements, the rounding residual shows the gap in thousandths of an inch. For add and subtract of exact sixteenth-inch values, the residual is always zero.
Why does machine control software show decimal feet instead of feet and inches?
Machine control systems display design elevations and coordinates as decimal feet because that's the format used by civil engineers in the US. The convert mode on this tool translates those decimal values into feet-inch-fraction format for easier field verification against a tape measure or plan sheet.
Can I multiply or divide a measurement?
Yes. Select Multiply or Divide, enter your measurement in Value A, and enter a plain number as the multiplier or divisor. The result is a length in feet-inches-sixteenths. Multiply is useful for calculating total lengths from a unit count. Divide is useful for splitting a run into equal spans or cuts.
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