Pace Calculator

How to use

1. 1Pick a mode at the top: Pace from time and distance for finished runs, Time from pace and distance for race projections, or Distance from pace and time when you have a fixed window to run.
2. 2Enter the inputs the mode asks for. Times accept HH:MM:SS, MM:SS, or plain seconds; pace accepts MM:SS; distances accept decimals.
3. 3Use the unit toggles next to Distance and Pace to switch between kilometers and miles independently. Tap any preset chip (5K, half marathon, easy 6:00 /km, etc.) to fill that field instantly.
4. 4Read the headline pace, pace per km, pace per mile, and equivalent speed in km/h and mph. Copy any single value with the inline Copy buttons.
5. 5Scroll down for an even splits table at every kilometer or mile up to your distance, plus race time predictions at 1 mile, 5K, 10K, half marathon, and marathon based on the Riegel formula.

About this tool

Pace Calculator works out running pace, finish time, distance, even splits, and projected race times for the most common race distances, all in your browser. Pick one of three modes at the top: Pace from time and distance turns a finished run into an average pace per kilometer and per mile (e.g. 25:00 over 5K becomes 5:00 /km and 8:03 /mi); Time from pace and distance projects a finish time at a target pace for any race distance from 1K up to 50K and beyond; Distance from pace and time answers the practical question of how far you can run in the time you have today. Distance and pace inputs each have an independent unit toggle so you can mix and match (enter distance in miles but read pace per kilometer, or the other way around) and one-click presets fill the seven most common race distances (1K, 1 mile, 5K, 10K, half marathon, marathon, 50K) and five everyday training paces from easy 6:00 /km up to race pace 4:00 /km. The result panel shows a large headline pace in the unit you picked plus pace per kilometer, pace per mile, and equivalent speed in km/h and mph, all with one-click copy buttons. An even splits table beneath shows the cumulative time at every full kilometer or mile up to the total distance plus a partial-unit row when the distance is not whole, exactly the layout you need to set splits on a watch or to plan an even-effort race. A separate Race time prediction panel uses Riegel's published formula T2 = T1 · (D2 / D1)^1.06 to project finish times at every common distance from your input, useful when you have a recent 5K and want to know what marathon time it implies for similar training and effort. All math runs locally on your device using exact unit conversions (1 mile = 1.609344 kilometers) and HH:MM:SS or MM:SS time parsing, so your training data and target times never leave your browser. Useful for race-day pacing plans, workout target paces, treadmill setups, post-run analysis, and answering common questions like what pace to hold for a sub-30 5K, sub-50 10K, sub-2 half, or sub-4 marathon.

Free to use. Works in your browser. No signup, no login.