How pace and speed convert
A mile is exactly 1.609344 km, so a per-mile pace is the per-km pace times 1.609344, and a per-km pace is the per-mile pace divided by the same number. A 4:00 km is a 6:26 mile. A 7:00 mile is a 4:21 km.
Speed is the inverse of pace. Divide 60 by the pace in decimal minutes: 5:30 per km is 5.5 minutes, so 60 / 5.5 = 10.9 km/h. Treadmills show speed, watches show pace, and this converter moves between all four units at once.
Finish times at a given pace
A finish time is pace multiplied by distance: 5 km, 10 km, 21.0975 km for the half marathon and 42.195 km for the marathon. These are even-pace times. Real races drift a few seconds per km with hills, wind and fatigue.
A pace you can hold for 5k is not a pace you can hold for a marathon. To predict a longer race from a shorter one, use the race time predictor, which applies Riegel's fatigue exponent instead of a straight multiplication.
Treadmill incline and outdoor pace
Uphill running costs more oxygen. The ACSM running equation puts the cost at VO2 = 0.2 × speed + 0.9 × speed × grade + 3.5 ml/kg/min, with speed in metres per minute and grade as a fraction. Setting that equal to a flat run gives a simple rule: the flat speed with the same cost is the treadmill speed × (1 + 4.5 × grade).
A treadmill also removes air resistance. Jones and Doust (1996) found that a 1% grade matched the oxygen cost of level road running for trained runners between 10.5 and 18 km/h. So 1% on the belt is your road pace, 0% is slightly easier than the road, and every percent above 1 adds roughly 4.5% to the equivalent speed. At 12 km/h and 5%, that is about 4:14 per km on a flat road.
The ACSM equation covers level and uphill running. It does not model downhill running, and it is a population average, so treat the result as an estimate of effort, not a measured value.
How it works
- 1Enter a pace or speed. Type a pace in min/km or min/mile, or a speed in km/h or mph, and pick the unit.
- 2Read the conversions. The other three units update at once, with finish times for the 5k, 10k, half marathon and marathon.
- 3Add a custom distance. Enter any distance in km or miles to get the finish time at that pace.
- 4Convert a treadmill run. Enter the treadmill speed and incline to see the equivalent flat treadmill pace and flat road pace.
Frequently asked questions
How do I convert min/km to min/mile?
Multiply the per-km pace by 1.609344. Convert it to seconds first: 5:00 per km is 300 seconds, times 1.609344 is 483 seconds, which is 8:03 per mile.
What pace is 10 km/h?
10 km/h is 6:00 per km and 9:39 per mile. Divide 60 by the speed to get minutes per km: 60 / 10 = 6.
What treadmill incline matches running outside?
A 1% grade. Jones and Doust (1996) found it matched the oxygen cost of level road running at speeds from 10.5 to 18 km/h. Below about 10 km/h the air resistance is small and 0% is already close.
What pace do I need for a sub-2-hour half marathon?
5:41 per km or 9:09 per mile. That is the same pace as a 4-hour marathon, held for half the distance.
What is a 7-minute mile in km?
A 7:00 mile is 4:21 per km, 13.8 km/h or 8.6 mph. At that pace a 10k takes 43:30 and a marathon 3:03:32.
Sources
- ACSM running metabolic equation. American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, metabolic calculations chapter: VO2 = 0.2·speed + 0.9·speed·grade + 3.5.
- Jones AM, Doust JH (1996). A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. J Sports Sci 14(4):321-327.
- NIST Special Publication 811. Guide for the Use of the International System of Units: 1 mile = 1.609344 km exactly.
Last updated 6 September 2026.