Running Pace Calculator

Type a distance + finish time (or distance + pace) and the page derives the other one, your speed in km/h and mph, race-time projections for the 5K, 10K, half, and marathon, and the training zone that pace falls into. Uses the published Daniels' Running Formula zone bands. Pure client-side, no upload.

Distance unit
What you know
km
Presets

Pace

per km
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Speed

live
— km/h

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Training zone

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Race-time projections

Holding the same effort level, here is what your equivalent 5K, 10K, half, and marathon finish times look like. Linear extrapolation from a steady pace — real-world racing will be a little slower at longer distances because of fatigue, but the gap is the classic "marathon is not just 8 × 5K" effect.

Race Distance Projected time Equivalent pace
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Daniels' zone reference

The training zone card picks the band that contains your pace. Bands are calibrated to VDOT 40–65 (roughly 17:30–38:00 5K). They are a starting point, not a prescription.

Zone Pace band % HRmax Effort
How pace, speed, and the zones are derived

Pace is the time it takes to cover one unit of distance. From a finish time and a distance, pace = time / distance (and then converted to per-km or per-mile). From a pace and a distance, time = pace × distance. Speed is the inverse: speed = distance / time, in m/s, then converted to km/h and mph.

Race-time projections assume a steady effort across distance — the kind of effort a single race from 5K to marathon would represent. Real-world, marathon is slower than 4.2 × 10K and 10K is slower than 2 × 5K, because of fatigue. We surface the linear projection as a useful "minimum reasonable" benchmark, not a prediction.

Training zones are taken from Daniels' Running Formula (2014). The bands are stated in equivalent pace-per-km ranges, calibrated to a population-level VDOT 40–65. They are: Repetition (< 3:00 /km, 105–120% HRmax), Interval (3:00–3:40, 95–100%), Threshold (3:40–4:20, 88–92%), Marathon (4:20–4:50, 78–84%), Easy (4:50–6:30, 65–78%), and Recovery (> 6:30, 55–65%).

The HRmax percentages are population averages. Individual HRmax has roughly a ±10 bpm standard deviation. Use the zones as a starting point and adjust to your own race history — anyone who has run a recent race already has a more accurate threshold than a formula can give.