Km to miles:
convert race distances, pace and speed

How many miles are in a kilometre?

One kilometre is 0.621371 miles. The mile is defined as exactly 1.609344 km, so a kilometre is 1 ÷ 1.609344 = 0.6213712 mile.

A mental shortcut is to multiply by 0.6. It lands within about 3.5% of the true value, which is fine for deciding whether a distance is 'a few miles'.

You are most likely to need it when a running app, a watch or a race entry from abroad uses the other unit from your own. Switching the display units on a watch changes only how the run is shown; the recorded distance stays the same, so you never need to redo a run.

This guide is built around running and cycling, where the conversion shows up in race names, pace and speed. If you are driving abroad and reading road signs in miles, the miles to km article is the one to use.

Km to miles formula and the 5/8 shortcut

1. 1Take the distance in kilometres.
2. 2Multiply by 0.621371 (or divide by 1.609344).
3. 3Round to two decimals for a race, or one decimal for training notes.

• 2 km = 1.24 mi
• 3 km = 1.86 mi
• 8 km = 4.97 mi
• 12 km = 7.46 mi
• 20 km = 12.43 mi

Values that are not listed can be built from the ones above. For 7 km, add 5 km (3.11 mi) and 2 km (1.24 mi) to get 4.35 mi, which matches 7 ÷ 1.609344 = 4.35 mi.

There is a neat fractional shortcut as well. Because 1.6 is the same as 8 ÷ 5, one kilometre is close to 5/8 of a mile. For 5 km, that is 5 × 5 ÷ 8 = 3.125 mi, against the exact 3.107 mi.

The 5/8 shortcut stays accurate to about 0.6% across any distance, so it is much better than the 0.6 multiplier on long runs. On a marathon, 0.6 gives 25.3 mi, which is nearly a mile short, while 5/8 gives 26.4 mi.

Race distances in kilometres and miles

The marathon's odd 0.2 comes from its length of 42.195 km: 42.195 ÷ 1.609344 = 26.219 miles, which is 26 miles 385 yards.

Some courses show both mile and kilometre markers. At the 10 km point you have run 6.21 miles, so you are about 344 m past the 6-mile marker. Knowing that stops you from thinking you have missed a marker.

A race that is advertised in miles, such as a '10-miler', is 16.09 km. Divide your target finishing time by the miles, then convert the result to kilometres if your watch is set to metric.

Worked example: a 6:00 per km pace in miles

Pace is time per distance, so the conversion goes the other way from distance. If a mile is longer than a kilometre, your time per mile is longer too.

Goal times use the same step. To finish a half marathon in 2 hours, you need 120 ÷ 21.0975 = 5.69 min per km, which is 5:41 per km, or 9:09 per mile. Set the watch to either unit and the target is identical.

Run that pace for 10 km (6.21 miles) and you finish in exactly 60 minutes. The numbers differ only because the unit of distance changes: 6.21 miles × 9:39 per mile is also an hour.

Speed: km/h to mph on a bike or treadmill

Speed converts like distance, with no extra step. Multiply km/h by 0.621371 to get mph.

• 8 km/h = 4.97 mph, an easy jog
• 12 km/h = 7.46 mph, a steady run
• 15 km/h = 9.32 mph, a quick run
• 25 km/h = 15.53 mph, a relaxed cycling speed
• 30 km/h = 18.64 mph, a strong ride

Cyclists use miles for a 'century', which is 100 miles or 160.9 km. A 100 km ride is therefore only 62.1 miles, and is called a 'metric century'. A typical 40 km club ride is 24.85 miles.

A treadmill set to 10 km/h runs at 6.21 mph, which is a 6:00 per km pace. A device that displays only mph can look slow if you are thinking in kilometres, so convert before you judge the effort.

Weekly distance and finish-time planning

Training plans from overseas are often written in miles. A 35 km week is 21.75 miles, and a 10-mile long run is 16.09 km. Keep a column of both in your log and the numbers will compare cleanly.

A common rule of thumb is to raise weekly mileage by no more than about 10% at a time. From 35 km, that is 38.5 km, or 23.92 miles. Whatever rule you follow, apply it in one unit so the maths stays simple.

Races with mile markers can confuse a metric watch. If your target is 5:30 per km, that is 8:51 per mile, so check each marker against 8:51 rather than 5:30.

For finishing time, multiply the pace by the distance in the same unit. A half marathon of 21.0975 km at 6:00 per km takes 126.6 minutes, which is 2 h 6 min 35 s.

Mistakes with km to miles

• Using the distance factor on pace. A 6:00 per km pace is not 3:44 per mile; it is 9:39.
• Rounding the 5K to 3 miles. It is 3.11 miles, so a 3.1-mile target is accurate.
• Mixing up km/h and min/km. One is speed and the other is pace, and they move in opposite directions.
• Mistaking nautical miles for statute miles. A nautical mile is 1.852 km, not 1.609 km.
• Rounding a 10K to 6 miles when you plan fuel or hydration. The extra 0.2 mile is about 340 m and matters in a close race.
• Converting only the distance when you compare two training plans. Convert the pace and the weekly total as well.

The surest check is a round trip. Convert km to miles, then multiply the miles back by 1.609344. You should recover your starting figure to within rounding.