Feet (ft) and Inches (in) explained
The foot and the inch are the working pair of the US customary system. The foot is 0.3048 meters exactly, and the inch is one twelfth of that — 2.54 cm. The duodecimal relationship is the reason imperial measurement survives in trades: twelve divides evenly by 2, 3, 4 and 6, so a carpenter can halve, third or quarter a foot and still land on a whole number of inches, which a decimal system will not do. That is also why inches are subdivided in halves, quarters, eighths and sixteenths rather than tenths. In practice most US measurements are written as feet and inches together, like 5' 10", and converting to total inches is usually the first step in any calculation.
Formula and worked examples
in = ft × 12Multiply feet by 12. A 6-foot door is 72 inches. An 8-foot ceiling is 96 inches. To convert a mixed measurement like 5 feet 10 inches, multiply the feet by 12 and add the inches: 5 × 12 + 10 = 70 inches. To go back, divide by 12 — the whole part is the feet and the remainder is the inches.
Feet (ft) to Inches (in) conversion table
Common Feet (ft) values converted to Inches (in). Every figure uses the same conversion factor as the calculator above.
| Feet (ft) | Inches (in) |
|---|---|
| 1 | 12 |
| 2 | 24 |
| 5 | 60 |
| 10 | 120 |
| 20 | 240 |
| 50 | 600 |
| 100 | 1200 |
Where you will use this
Height stated in feet and inches
US forms, sports rosters and dating profiles quote height as feet and inches. Converting to total inches first is what lets you compare two heights arithmetically or convert onward to centimeters by multiplying by 2.54.
Cutting lumber and sheet goods
US lumber is sold in foot lengths but cut lists are written in inches. An 8-foot 2×4 gives 96 inches of usable length, so four 24-inch legs use exactly one board with nothing to spare for saw kerf.
Reading room and appliance dimensions
Floor plans list room sizes in feet while appliance specifications are in inches. A 30-inch range needs 2.5 feet of counter gap, and checking that against a 10-foot wall means converting the wall to 120 inches first.