Pace Calculator
Enter a time and a distance to get your running pace, per-kilometer or per-mile splits for the common races, and the treadmill speed that matches. Everything runs in your browser.
How to use
- Pick a race distance (5K, 10K, half marathon, marathon) or choose custom and enter your own in kilometers.
- Type your finish time as minutes and seconds, or hours, minutes, and seconds for longer races. The pace updates as you type.
- Read your pace per kilometer and per mile, plus the equivalent speeds, then open the splits card for a row at every kilometer or mile mark.
- Use the treadmill card to turn a belt speed into a pace, or a target pace into the speed to set on the treadmill.
How the pace is calculated
Pace is your finish time divided by distance, shown in minutes and seconds per kilometer or per mile. The tool works in whole seconds per unit and formats them for display, so the same input always produces the same output with no rounding drift. One mile is taken as exactly 1.609344 kilometers, and the half marathon as 21,097.5 meters.
Splits assume an even effort: each full kilometer or mile gets the same pace, and the last row covers whatever distance remains. Real races rarely run even, so use the table as a pacing plan rather than a prediction.
Frequently asked questions
Is any of my run data uploaded?
No. The calculator runs entirely in your browser tab. Distances and times you enter are processed on your device, nothing is sent to a server, nothing is stored, and the page sets no cookies. The ad slots on the page are served by third-party networks, which follow their own privacy policies.
How are the splits calculated?
Your finish time is converted to a pace in whole seconds per kilometer or per mile. Every full unit of the race shows that pace, and the final partial split absorbs the rounding so the table always sums to the time you entered. A split can never come out negative, even when rounding pushes the running total to the finish early.
Why does my GPS watch show a slightly different pace?
Watches compute pace from a GPS-measured distance that wobbles with tree cover, tall buildings, and signal quality, and they keep fractional seconds. This tool uses the exact distance and time you enter and rounds the pace to the nearest second, so small differences from your watch are normal.
Does the treadmill conversion match my gym treadmill?
The arithmetic is exact: a belt speed in km/h or mph maps straight to minutes per kilometer or per mile. The belt itself is the weak link. Treadmills are calibrated loosely and a belt set to 12 km/h often runs a percent or two fast or slow, so treat the converted pace as what the machine claims, not what your legs did.