How this instrument works
Feet were never one thing. Rome's pes ran close to 296 mm; the French crown's pied du roi, abolished at the Revolution, measured about 324.8 mm, some 6.5% longer than its English cousin; and medieval English guilds are recorded using foot lengths that drifted by region and by trade before any national standard existed. England's own bar shrank quietly too — the bronze standard cast to replace the yard lost in that fire was found, within decades of its casting, to be contracting on its own from residual stresses set in the metal.
That drift ended on 1 July 1959, when standards bodies in the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa fixed one international yard at 0.9144 m by agreement. A third of that yard gives a foot of exactly 0.3048 m — written as a fraction, 381⁄1250, which terminates cleanly and carries no measurement uncertainty at all. Every digit past the decimal point in a conversion is arithmetic, not tolerance.
Feet held their ground where metres never fully arrived. American building trades still frame houses, quote ceiling heights and sell lumber in whole feet; US real-estate listings advertise square footage rather than square metres; pilots worldwide, including over metric Europe, report altitude and cruising level in feet. Everywhere else — road signs, medicine, engineering drawings, most of world sport — metres and millimetres do the work instead, which is why this pair of units still needs converting daily rather than being a historical curiosity.
- Type your length into the Feet (ft) field; it opens at 10 so you can see the factor working immediately.
- Read your result on the Metres (m) line — it recalculates to six decimal places on every keystroke.
- For a height like 5 ft 9 in, turn the inches into a decimal first: 9 ÷ 12 = 0.75, so enter 5.75.
- Reversing direction? Divide your metric figure by 0.3048, or simply nudge Feet (ft) until Metres (m) matches your target.
- Keep full precision until the final answer — round only what you display, never a number you plan to convert again.
Worked example — a regulation 10-foot basketball hoop
Basketball's rim height has been fixed at 10 feet above the court since James Naismith nailed up his first peach basket in 1891, and it has never changed at any level of the sport since. Type 10 into Feet (ft) and Metres (m) reads 3.048 — not an approximation, because 10 × 0.3048 terminates at three decimal places with nothing left over.
That number travels well: a European gym building a regulation court to FIBA specifications orders backboard supports rated for exactly 3.048 m, and nobody on either side of the Atlantic needs to argue about rounding. Compare it with a doorway instead and the same arithmetic holds — an 8 ft ceiling common in American homes stands at 2.4384 m, again exact to the millimetre, no tolerance stacked in along the way.
Questions
Is 0.3048 an exact conversion factor, or is it rounded?
Exact. The 1959 international yard and pound agreement fixed one yard at precisely 0.9144 m, so one foot — a third of that yard — comes out to exactly 0.3048 m with zero uncertainty. Nothing about this factor was measured against a physical object; it is a legal definition adopted simultaneously by six English-speaking countries. Any rounding you notice in a converted answer comes only from how many decimal places you choose to keep on screen.
Does a US survey foot give a different answer?
By a hair, which is exactly why it was retired. The survey foot used an older ratio of 1200⁄3937 m, about 0.304800610 m — roughly two parts per million longer than the international foot used here. NIST and NOAA withdrew it from official use at the end of 2022. Over 10 ft the gap is a few millionths of a metre, invisible to any tape measure, but on state coordinate grids spanning millions of feet it can add up to several feet, so old survey data is worth checking before converting.
How do I convert a height given in feet and inches?
Turn the inches into a decimal fraction of a foot first, then multiply the whole figure by 0.3048. Nine inches is 9 ÷ 12 = 0.75, so 5 ft 9 in becomes 5.75 ft, and 5.75 × 0.3048 = 1.7526 m. A common slip is typing 5.9 instead of 5.75 — treating inches as if they were a decimal already — which adds nearly 5 cm to the result.
Why do US real-estate listings use square feet instead of square metres?
Because the underlying linear unit never switched. American property law, mortgage appraisal standards and building codes have measured floor area in feet since long before metrication was ever debated, and no federal mandate forced a change the way several other countries carried out. One square metre is roughly 10.764 square feet, which is why a listing's 'sq ft' figure looks so much larger than the same home's area would in square metres.
Why do pilots still report altitude in feet worldwide?
Because aviation standardised on feet while American and British manufacturers dominated instrument design, and re-marking every altimeter, chart and air traffic procedure on Earth would cost vastly more than the inconsistency does. Vertical separation minima, cruising levels and runway elevations are published in feet almost everywhere, including over metric Europe — mainland China is the well-known exception, assigning cruising altitudes in metres instead.
Is there a quick mental shortcut for feet to metres?
Take a third of your figure, then trim about a twelfth off that. Thirds alone overshoot by roughly 9%, so 30 ft becomes 10, minus about 0.9, landing near 9.1 m against an exact 9.144 m. Reverse direction is friendlier: one metre is a little over 3 ft 3 in, so triple your metres and add a small correction. Save shortcuts for sanity checks — anything built, billed, or filed deserves the full 0.3048 factor.