ランニングペース変換・レースタイム予測ツール

計算の仕組み

Everything is derived from one number: seconds per kilometre. In Time + distance mode that is your entered time divided by the distance, converted at 1 mile = 1.609344 km; in Pace directly mode you supply it outright. From there the tool prints min/km, min/mi, km/h and mph. Race predictions use Riegel's formula, T₂ = T₁ × (D₂ ÷ D₁)^1.06, applied to 1 mile, 5K, 10K, the half marathon at 21.0975 km and the marathon at 42.195 km.

Riegel scales from whatever distance you entered, which makes that entry the most consequential input on the page — a 5K predicts an optimistic marathon, a recent half predicts a believable one. The four presets load 5K · 25:00, 10K · 50:00, Half · 1:45 and Marathon · 3:45 as time-and-distance pairs in kilometres. Pace directly mode has no distance field and assumes 5 km, so every prediction there extrapolates out from a 5K.

The 1.06 exponent is a population fit, not your physiology. It assumes you have actually trained for the longer distance and says nothing about heat, hills, fuelling or course profile, so marathon predictions from short races habitually read fast. The splits table is always per kilometre even when you enter miles, and it stops at 42 rows, so anything beyond marathon distance gets quietly truncated at that point.

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