One metre is 3.280839895 feet. The relationship is fixed by definition rather than by measurement, which is why it has not changed since 1959 and will not change again: the foot is defined as exactly 0.3048 metres, and everything else follows from that one number.
About the units
The metre is the base unit of length in the SI system, and since 1983 it has been defined by the speed of light — the distance light travels in vacuum in 1/299,792,458 of a second. That definition is deliberately circular-looking: the speed of light was fixed as an exact constant, and the metre now hangs off it. The foot is older and messier. It descends from body-based measures used across Europe, standardised very differently from place to place, and only became a single unambiguous quantity with the International Yard and Pound Agreement of 1959, when the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa agreed that one yard would be exactly 0.9144 metres. A foot is a third of that.
The exact factor
Because the foot is defined in terms of the metre and not the other way round, the two directions behave differently. Feet to metres is exact: multiply by 0.3048 and the answer terminates. Metres to feet is not: 1 ÷ 0.3048 = 3.28083989501312335958..., a repeating decimal that no finite number of digits captures. Any tool that shows you "3.28" has rounded, and for most purposes that is fine — the error is about six millimetres per ten metres. One complication survives in American land records: the US survey foot, defined as 1200/3937 metres, is very slightly longer than the international foot. The difference is two parts per million, which is invisible over a room and about 3 cm over 15 kilometres. It was officially retired at the end of 2022, but older surveys and deeds still use it.
Where you meet this conversion
This is the conversion behind almost every cross-Atlantic misunderstanding about size. Aviation uses feet for altitude worldwide, including in metric countries, so flight level 350 means 35,000 feet — about 10,668 metres. Building trades in the US quote ceiling heights, lumber and room dimensions in feet and inches while the drawings behind them may be metric. Athletics keeps both: the marathon is metric, the long jump is measured in metres and reported in feet in American coverage. And anyone reading a hiking map abroad meets it immediately, because summit heights switch units at the border.