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Running pace calculator

Work out pace, time or distance for a run and see a full splits table.

Input
3
Output
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Running pace calculator
Give this calculator a finish time or a pace and it works out everything else: total time, pace per kilometer or mile, the equivalent speed, and a full table of split times at every kilometer or mile of the run. Paste one time or pace per line to check several goals at once — a 5K target next to a marathon one — and each line gets its own labeled splits table.
Set the distance from four race presets (5K, 10K, half marathon, marathon) or switch to a custom distance in your preferred unit. Choose whether each input line is a finish time or a pace/speed value, and whether pace displays as time per unit or as a speed. The split strategy builds a negative split (slower start, faster finish — the pacing most coaches recommend) or a positive split (fast start that fades) instead of even pacing, with the variance between first and last split set as a percentage. The treadmill incline option adjusts the target pace for a given grade so it matches the effort of the equivalent flat-ground pace, using the standard ACSM running equation — a reasonable approximation for moderate grades, not lab-grade physiology.
Times accept H:MM:SS or MM:SS (a bare number is read as minutes), with a comma or dot as the decimal mark. Kilometer and mile paces show side by side by default, so a separate conversion is never needed, and the calculator names the exact line and text of anything it cannot parse rather than failing silently.
Everything runs locally in your browser — training paces and race plans are never uploaded anywhere. Copy the result, download it as a .txt file, clear the input, or send the output back into the input to tweak one more option.
FAQ
Can I give a pace instead of a finish time?
Yes. Set "Each line is a" to "Pace or speed" and enter a pace (MM:SS) or, with "Pace as" set to speed, a plain number of kilometers or miles per hour.
What does the split strategy option change?
It reshapes the table of splits around your average pace: negative starts slower and finishes faster, positive starts faster and fades, and the variance slider sets how far the first and last split drift from even pace.
How accurate is the treadmill incline adjustment?
It uses the widely taught ACSM running equation to estimate the flat-ground pace with equal effort. It is a solid approximation for moderate inclines, not an exact physiological measurement.
Can I calculate multiple races at once?
Yes. Put one time or pace per line and each one gets its own labeled splits table in the output, using the same distance and options.
Is my training data uploaded anywhere?
No. The calculator runs entirely in your browser—your times and paces never leave your device.