Convert ft to mi

A foot is twelve inches, and it is the unit heights and room sizes are quoted in across the United States. Aviation quotes altitude in feet almost everywhere, including in countries that are metric for everything else; China is the exception, where controllers clear aircraft in metres.

A mile is 1,760 yards — a number that comes from a Roman thousand paces, adjusted by an Elizabethan statute to fit the furlong. It is exactly 1,609.344 metres.

Going this way is a division, and by a whole number: 5,280 of these fit into one mile with nothing left over. The awkwardness is only that the answers come out as fractions — a third of a mile, a twelfth of one — rather than as the round figures the other direction gives you.

Nothing is lost to rounding even so. The division is exact, and if your answer will not sit still as a decimal — 0.0833… and friends — that is the fraction showing through, not an error creeping in.

The number is worth memorising because nothing derives it. It is 5,280 feet to a mile, and the reason a runner meets it more than anybody else is that trail data quotes distance in miles and climbing in feet, so the two most important numbers about a route are in units three orders of magnitude apart. A 12-mile route with 3,600 feet of gain is not obviously anything until one of them moves.

Moved into the same unit, it becomes legible. Three thousand six hundred feet is 0.68 of a mile of vertical, over twelve miles of horizontal — a ratio of about one in eighteen, which is a steady, runnable climb. The conversion is doing something more useful here than answering a question: it is putting two axes on a comparable footing.

Every trail profile you will read is drawn with a vertical axis exaggerated many times over, because a true-scale drawing of a 10-mile route with 2,000 feet of gain would be a nearly flat line. That exaggeration is honest and necessary and it also makes climbs look like walls. Converting the gain to miles is the fastest correction: 2,000 feet is 0.38 of a mile, spread across ten.

It also explains why two routes with the same headline numbers feel different. Two thousand feet gained in one continuous climb and 2,000 feet gained across fourteen small rises are the same figure and not the same day; the profile shows the difference and the total conceals it. The conversion tells you the size of the problem, not its shape.

The mile is Roman. Mille passus means a thousand paces, where a pace was a double step — left foot to left foot — of about five Roman feet, so the Roman mile was roughly 5,000 of their feet and about 1,479 metres. That is a genuinely designed unit: a soldier could count it, and the Roman army did, planting a marker at every one.

What broke the round number was England already having its own land measure. Fields were laid out in furlongs of 660 feet, and eight furlongs was near enough to a Roman mile to be called one. Rather than change the furlong, which would have changed every field boundary in the country, the statute of 1593 changed the mile: eight furlongs of 660 feet, so 5,280. The odd figure is the price of not redrawing the map.

Tower running quotes everything in feet and floors, and the conversion makes the numbers comparable to a hill. The Empire State Building run climbs about 1,050 feet over 1,576 steps, which is a fifth of a vertical mile; doing it five times over would be the full 5,280. A typical building storey is 10 to 12 feet, so a vertical mile is somewhere around 450 to 500 floors.

The same arithmetic makes sense of a stairwell workout. A domestic flight of 13 steps at about 7 inches a step is roughly 7.6 feet, so a vertical mile is about 700 flights. These figures are worth having because vertical effort is badly served by intuition — most people underestimate how much climbing is in a modest hill walk and overestimate what a stair session adds up to.

One per cent of a mile is 52.8 feet, and that single constant turns any elevation figure into a slope. A road gaining 300 feet in a mile is a 5.7 per cent climb; 528 feet in a mile is exactly ten per cent; 1,000 feet in a mile is nearly nineteen, which is beyond what most roads are built to. Signposted gradients and elevation profiles finally become the same language.

Railways use the same relationship expressed as a ratio. A gradient of 1 in 100 is one per cent, which is 52.8 feet per mile, and the steep sections of British main lines at 1 in 37 work out at about 143 feet per mile. Converting feet of gain to miles and then to a ratio is more informative than the raw figure, because a gradient is what the legs or the engine actually respond to.

Resorts advertise vertical drop in feet, and it is a single subtraction — summit elevation minus base elevation — rather than a sum of anything. A drop of 3,000 feet means the mountain is 0.57 of a mile tall from the lift base, and a skier taking ten runs has descended nearly six vertical miles, which is a much larger number than the mountain’s own.

Cumulative vertical and vertical drop are therefore different measurements that share a unit, and only the cumulative one behaves like a distance. This is the same distinction that matters on a trail: net elevation change is a subtraction and elevation gain is a sum, and a route that finishes where it started has a net of zero and can still have five thousand feet of climbing in it.

Until recently the United States had two feet. The international foot is exactly 0.3048 m; the US survey foot was 1200/3937 m, longer by about two parts in a million, and it was kept alive for a century because changing it would have invalidated the coordinates of every parcel of land already surveyed. A mile in survey feet is about three millimetres longer than a mile in international feet.

That difference is invisible on a trail and matters over a state: two parts in a million across a thousand miles is about ten feet, which is a fence line. The survey foot was formally retired for new work at the end of 2022, so anything measured since then is in international feet. Historical elevation and boundary data is not, and the two should not be mixed without knowing which is which.

Two people walking the same route will come home with elevation totals hundreds of feet apart, and neither device is broken. Satellite positioning is far weaker vertically than horizontally, so a watch relying on it alone reports a noisy altitude that a naive sum turns into climbing that never happened. A barometric altimeter is smoother and drifts with the weather instead: a front passing during a long day can add or remove a few hundred feet over the course of it.

The other half of the discrepancy is the threshold each device uses before it counts a rise at all. A watch that ignores changes under ten feet will report far less gain on rolling ground than one that counts everything, and neither figure is wrong so much as differently defined. Converting to miles makes the size of the disagreement legible — 400 feet of dispute is 0.076 of a vertical mile — and it is the reason a route’s published gain should be treated as a description rather than a measurement.