Meters to Feet

One meter is about 3.28 feet — multiply by 3 and add 10% for a quick head estimate.

The foot is defined from the metre, and the definition is exact

Since the international yard and pound agreement of 1959, a foot is exactly 0.3048 metres. Not approximately — the foot has no independent existence any more, and every imperial length in this family is a defined multiple of a metric one.

Worth saying because people reach for more decimal places expecting to find a truer number underneath. There isn't one — 0.3048 is the whole value, and 3.280839895013… is simply one divided by it.

Except that the United States had two feet until the end of 2022

Before 1959 the American foot was 1200/3937 of a metre — a ratio fixed in 1893, when the metre was the physical standard and the foot was pinned to it. That works out to 0.304800609601219 m, which is larger than the modern foot.

The 1959 agreement shortened the foot, and surveying could not follow. Every state plane coordinate system in the country was already published in the old unit, and recomputing them would have moved every recorded property corner. So the old value was kept, renamed the US survey foot, and the country ran two feet at once for sixty-three years. NIST and the National Geodetic Survey retired it at the end of 2022; it persists in older survey data, in state statutes, and in any drawing that predates the change.

The gap is 2.000004 parts per million. Across a room it is nothing: a 1000 ft building measures 0.61 mm different.

Two parts per million becomes two feet, because coordinates are large

State plane coordinates are measured from an origin placed far outside the zone, specifically so no coordinate is ever negative. That puts working values in the hundreds of thousands or millions of feet — and the disagreement scales with them.

At a coordinate of one million feet the two definitions are exactly two feet apart. That is not a rounding error, it is a different place — the same physical point described in two units whose names are both "feet". The tell is that the disagreement grows in proportion to the number: a fixed offset is a datum problem, an offset that grows is a unit problem.

The converter above uses the international foot, which is the right one for everything outside legacy survey work. Converting 1500 m gives 4,921.2598 ft international and 4,921.2500 ft survey — a longer foot means fewer of them, so the survey figure is always the smaller number.