Article — MM to Foot Converter
MM to feet: convert millimetres to feet exactly
One foot equals exactly 304.8 millimetres. To convert millimetres to feet, divide by 304.8. To go the other way, multiply by 304.8. The factor is exact by international treaty (the 1959 Yard and Pound Agreement), not a measurement. The reciprocal — 1 mm in feet — is 1/304.8 = 0.003280839895... a non-terminating decimal.
The converter above runs in both directions and handles up to six decimal places. Quick presets cover 100 mm (a typical machine screw head), 305 mm (one foot rounded), 1,000 mm (one metre), 3,048 mm (ten feet), and 5,000 mm (just over sixteen feet).
How many mm in a foot?
One international foot equals exactly 304.8 millimetres. The number is not rounded; it is the defined value. Every other length unit in the imperial system traces back to this exact relationship through the inch (25.4 mm) and the yard (914.4 mm).
- 1 inch = 25.4 mm (exact)
- 1 foot = 12 inches = 304.8 mm (exact)
- 1 yard = 3 feet = 914.4 mm (exact)
- 1 mile = 5,280 feet = 1,609,344 mm = 1.609344 km
All four definitions are exact because the inch was redefined as 25.4 millimetres by treaty. The metric system is the basis; the imperial units are derived. This was the deal six English-speaking countries signed in 1959.
MM to feet formula
The conversion is one division:
feet = mm / 304.8 (mm to ft)mm = feet × 304.8 (ft to mm)mm / 300 ≈ feet (mental math, ~2% off)Worked example. A standard door height of 2,032 mm: 2,032 ÷ 304.8 = 6.667 feet = 6 ft 8 in. Reverse: 8 ft × 304.8 = 2,438.4 mm.
Why 1 foot equals 304.8 mm
Before 1959, the imperial foot varied slightly between countries. The British imperial foot was defined against a physical bar held by the Board of Trade in London. The US foot was defined separately and was about 0.0002% longer (around 2 parts per million). Engineering across the Atlantic required constant correction tables.
In 1959 the US, UK, Canada, Australia, New Zealand, and South Africa signed the International Yard and Pound Agreement, which fixed the yard at exactly 0.9144 metres. From that, the foot became 0.3048 metres = 304.8 mm. The inch became 25.4 mm. The pound was defined as exactly 0.45359237 kilograms in the same treaty.
The metric kilogram was the only SI base unit defined by a physical object (the International Prototype Kilogram, kept outside Paris) from 1889 until 2019, when it was redefined using the Planck constant. The metre had already moved off a physical bar in 1960 and off the krypton-86 wavelength in 1983. Since 1983 the metre has been defined by the speed of light, which means 304.8 mm is itself anchored to a fundamental physical constant.
Common mm-to-feet conversions
Reference points worth memorising:
- 25.4 mm = 1 inch = 0.0833 ft
- 100 mm = 3.94 in = 0.328 ft
- 152.4 mm = 6 in = 0.5 ft
- 304.8 mm = 12 in = 1 ft
- 500 mm = 19.69 in = 1.640 ft
- 914.4 mm = 36 in = 3 ft (1 yard)
- 1,000 mm = 39.37 in = 3.281 ft (1 metre)
- 1,524 mm = 60 in = 5 ft
- 3,048 mm = 120 in = 10 ft
- 5,000 mm = 196.85 in = 16.404 ft
MM to feet in construction
Construction is the application where mm-to-feet conversions show up most often. North American building codes use feet and inches; European codes use millimetres. Cross-border projects, IKEA furniture in American homes, and German machine tools on US factory floors all require translation.
Useful construction reference points:
- Standard door height = 2,032 mm = 6 ft 8 in
- Stud spacing (16 in OC) = 406 mm
- Stud spacing (24 in OC) = 610 mm
- Plywood sheet = 1,219 × 2,438 mm = 4 ft × 8 ft
- 8-foot ceiling = 2,438 mm
- 9-foot ceiling = 2,743 mm
- 30-inch counter = 762 mm
- 36-inch counter = 914 mm
International foot vs US survey foot
Until 2022, the US recognised two different feet for different purposes. The international foot (304.8 mm exact) was used for everyday measurement, engineering, and most legal definitions. The US survey foot was defined as 1200/3937 metres ≈ 304.8006 mm, about 2 parts per million longer than the international foot. The survey foot was used for land measurement, state plane coordinate systems, and some federal mapping.
NIST and NOAA jointly retired the US survey foot in 2022. New surveys use the international foot. Existing records remain valid; the difference (about 3 mm per mile, or one foot per about 95 miles) is rarely material outside precise land-boundary work. Some states resisted the change and kept survey-foot conventions for local cadastral purposes.
Mental math mm-to-feet tricks
Divide by 300 for a rough estimate. The error is 1.6% — 304.8 / 300 = 1.016. A 1,500 mm wall: 1,500 / 300 = 5 ft (true: 4.92 ft). A 2,400 mm board: 2,400 / 300 = 8 ft (true: 7.87 ft). Always slightly overestimates.
Use 25 mm per inch. The real factor is 25.4, so dividing by 25 gives inches that are 1.6% too high. 100 mm / 25 = 4 in (true: 3.94). Same error direction as the foot trick — and consistent, because foot = 12 inches.
To convert mm to feet and inches together: divide mm by 304.8 for total feet, then multiply the decimal part by 12 for inches. Example: 1,778 mm ÷ 304.8 = 5.833 ft. 0.833 × 12 = 10 in. So 1,778 mm = 5 ft 10 in.
Common mm-to-feet mistakes
Confusing feet and decimal feet. 6.5 ft is not 6 ft 5 in. 6.5 ft = 6 ft 6 in (half of 12 inches). Always convert the decimal part to inches separately, or use the calculator's fractional output.
The factor 304.8 is exact. Substituting 300 or 305 introduces error on every conversion. For mental math the error is acceptable. For engineering, blueprints, or precision machining, use 304.8 or the calculator. A 0.5% error on a 10-metre dimension is 50 mm — bigger than the kerf of a circular saw.
Mixing imperial and US survey units. Older USGS maps, state plane coordinates from the 1970s, and some land records use the survey foot. Newer documents use the international foot. The 6 ppm gap matters for legal boundary descriptions; consult a licensed surveyor when stakes are high.
Treating the inch as 25 mm. The real value is 25.4 mm exact. Rounding the inch to 25 makes every conversion 1.6% short. Hardware and machine threads designed at 25.4 will not match parts manufactured at 25.