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Training · FREE & BROWSER-LOCAL

Running pace & speed calculator

Calculate running pace, duration or distance, including from treadmill speed in km/h or mph. Use race presets and view even splits, including the final partial kilometer or mile.

The method behind the numbers ↗

Your inputs

Estimates update as you edit.

Your calculation

YOUR NUMBERS, EXPLAINED
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A little context. A clearer result.

Enter your values to calculate instantly, or load the illustrative example.

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Keep a useful calculation

Nothing is saved automatically. Save stores these inputs in this browser. Sharing exposes all current calculator inputs in the link to anyone who receives it, and in browser history.

Load / manage saved calculations →

How this calculator works

Pace = duration / distance; duration = pace × distance; distance = duration / pace. Speed = distance / hours. Internal time is seconds and internal distance is kilometers. One international mile is exactly 1.609344 km.

For a treadmill speed, choose duration from speed + distance or distance from speed + duration. Duration in hours = distance / speed; distance = speed × hours; pace in seconds per km = 3600 / km/h. Metric speed is km/h; imperial speed is mph. Switching units preserves the physical speed.

Enter times as min:sec (25:00) or hr:min:sec (1:25:00). A bare 25 is ambiguous and rejected. Seconds and the middle component of hr:min:sec must be below 60; fractional seconds are allowed. Pace uses the selected kilometer or mile unit.

Presets set distance to 5 km, 10 km, 21.0975 km or 42.195 km and select pace calculation. Each whole kilometer or mile gets equal time; the final partial split gets time in proportion to its length. Switch display units to see the other split system.

Reading your result

This is even-pace arithmetic, not a forecast of running ability. Weather, elevation, stops, course measurement and fatigue can change an actual finish. Each displayed split and elapsed time rounds independently to whole seconds.

Illustrative worked example

5 km in 25:00 gives 5:00 per km and 12 km/h. In miles this is approximately 8:03 per mile over 3.1069 miles; the last 0.1069 mile is a partial split. Entering 12 km/h and 5 km also gives 25:00. At 6 mph, 3 miles takes 30:00 at 10:00 per mile.

Supported inputs & limitations

Adult recreational planning with distances 0.1–200 km, durations up to 48 hours, and pace 1:00–60:00 per km (speed 1–60 km/h, about 0.621–37.282 mph). Zero, negative and out-of-scope inputs or calculated results are rejected. Only the selected mode's inputs are saved or shared. Treadmill incline and differences between treadmill and outdoor running are not modelled.

Sources & methodology

These primary sources support the method and context. They do not endorse helsy or verify this implementation.