Convert feet to millimetres
1 ft = 304.8 mm
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How many millimetres are in a foot?
One foot is 304.8 millimetres. To convert any amount, multiply by 304.8. Going the other way, one millimetre is 0.0032808399 feet.
What is the formula to convert ft to mm?
Multiply the foot figure by 304.8. So mm = ft × 304.8. For a quick mental estimate, multiplying by about 305 gets you within a percent or so, which is close enough for most everyday purposes.
What does a foot actually look like?
One foot is about the length of a standard ruler. The foot is exactly 0.3048 metres. It survives in aviation worldwide — altitudes are given in feet almost everywhere, including in fully metric countries.
And what is a millimetre?
One millimetre is roughly the thickness of a credit card, which is 0.76 mm. The millimetre is the working unit of engineering drawings and machining tolerances almost everywhere metric is used, because it avoids decimals for most part dimensions.
Is this conversion exact?
Yes. Since the 1959 international yard and pound agreement, the imperial and metric systems are related by exact definitions rather than measurements — the inch is exactly 25.4 mm and the pound exactly 0.45359237 kg. Everything derived from those, including this conversion, is therefore exact. Round at the end rather than partway through, since rounding ft before converting introduces an error the conversion then multiplies.
About ft to mm
How to convert feet to millimetres
Multiply by 304.8. One foot is 304.8 millimetres, and one millimetre is 0.0032808399 feet.
mm = ft × 304.8
Worked example
10 ft = 3048 mm. For a sense of scale, one foot is about the length of a standard ruler, and one millimetre is roughly the thickness of a credit card, which is 0.76 mm.
About the foot
The foot is exactly 0.3048 metres. It survives in aviation worldwide — altitudes are given in feet almost everywhere, including in fully metric countries.
About the millimetre
The millimetre is the working unit of engineering drawings and machining tolerances almost everywhere metric is used, because it avoids decimals for most part dimensions.
Quick reference
| feet | millimetres |
|---|---|
| 1 ft | 304.8 mm |
| 2 ft | 609.6 mm |
| 5 ft | 1524 mm |
| 10 ft | 3048 mm |
| 25 ft | 7620 mm |
| 50 ft | 15240 mm |
| 100 ft | 30480 mm |
| 1000 ft | 304800 mm |
Getting it right
This conversion is exact by definition, so the only limit on accuracy is how many digits you keep. Round at the end rather than partway through — rounding ft to a whole number before converting introduces an error that the conversion then multiplies.
Other length conversions
Convert millimetres back to feet, or pick any other pair with the full unit converter. Related: ft to km, ft to m, ft to cm.