Convert foot to inch.

Convert foot (ft) to inch (in). This is a fixed-ratio conversion — multiply the input by the factor below.

Formula

in = ft × 12

Reference values

Things to watch for

• The international inch is exactly 25.4 mm (defined since 1959), so length conversions are exact, not approximations.
• Use mm for engineering drawings, cm for everyday measurements, m for room dimensions, km for distances.
• 1 mile = 1.609344 km (exact). Nautical miles are different: 1 nmi = 1852 m exactly (defined for nautical use).

What is a foot?

One foot equals exactly 12 inches or 0.3048 meters. Building heights, room dimensions in the US, aircraft altitudes, and lumber lengths.

What is a inch?

The international inch is defined as exactly 25.4 millimeters since 1959, when the US, UK, and Commonwealth countries unified their definitions. US construction lumber, screen sizes (TV diagonals, phone screens), printing measurements, and pipe sizing.

Everyday reference points for ft

Concrete examples often help when a unit doesn't have an intuitive feel. 8 ft is about the height of a residential ceiling; 100 ft is about the length of a US football end zone; and 300 ft is roughly the height of a 30-story building.

How to convert foot to inch

To convert a value from foot (ft) to inch (in), apply the conversion factor shown in the formula above. The calculation is the same whether you do it by hand, in a spreadsheet, or with the live converter on this page.

Steps:

1. Take your input value in ft.
2. Apply the formula in = ft × 12.
3. The result is your value in in.

For repeated calculations, save the formula in a spreadsheet or use the live converter at the top of this page — it handles the math automatically and displays the result as you type.

Frequently asked questions

How do I convert ft to in?

Apply the formula ft → in shown above, or just type your value into the converter at the top of this page. The result updates instantly.

Which is bigger, ft or in?

This depends on the conversion ratio in the formula. If the factor multiplied by your value gives a larger number, then in is the smaller unit (so it takes more of them to express the same quantity). If the result is smaller, then in is the larger unit.

When would I use ft versus in?

Both units measure length, so the choice depends on context. Foot is typically used for engineering specs, construction, navigation, and everyday measurement; inch similarly. Most professional fields standardize on one or the other based on regional conventions or technical tradition.

How precise is this ft to in conversion?

The conversion factor shown is the internationally defined exact value (or the best-published approximation if the relationship is irrational, like degrees-to-radians). The live converter on this page uses double-precision floating-point math, accurate to about 15 significant digits — far beyond any practical engineering need.

Is the conversion ratio exact, or an approximation?

Most unit conversions between SI metric units, and between SI and US customary units, have been formally defined as exact values since the 1959 international yard-pound agreement and subsequent SI redefinitions. Exceptions are unit pairs that involve irrational numbers (radians, e.g.) or empirical conversions (like food calories, which depend on temperature). When in doubt, consult the formula at the top of this page.

Related conversions

See also