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Calculate pace, predict race times via Riegel formula, and get training zones.
Common: 5K = 5, 10K = 10, Half marathon = 21.1, Marathon = 42.2
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Enter distance and time, then click Calculate
Riegel Formula: T₂ = T₁ × (D₂ / D₁)^1.06. Published by Pete Riegel in Runner's World (1977). The exponent 1.06 accounts for physiological fatigue with distance. Best for distances within 2× of your training distance.
Training Zones: Based on Jack Daniels' VDOT system (Daniels' Running Formula, 3rd ed.). Easy (59–74% vVO₂max), Marathon, Threshold (~88% VO₂max), Interval (98% VO₂max), Repetition (105–120%).
Riegel formula: T2 = T1 × (D2/D1)^1.06. A 25-minute 5K predicts ~52-minute 10K. Accuracy decreases for distances far from your training distance.
Based on Jack Daniels' VDOT: Easy (60–79% of race pace), Marathon pace, Threshold (lactate threshold, ~1-hr race pace), Interval (5K pace), Repetition (1-mile pace). Each builds different adaptations.
A comfortable conversational pace is typically 7–9 min/km (11–14 min/mile). The talk test: if you can speak full sentences, you're in the easy aerobic zone.
Get pace per kilometre and per mile, full split tables, training-pace zones, and race-time predictions for 5K, 10K, half marathon, and marathon distances.
Pace is simply finishing time divided by distance, but useful pacing also requires per-segment splits and consistent intensity.
Riegel's endurance formula extrapolates between race distances: t₂ = t₁ × (d₂/d₁)¹·⁰⁶. The exponent 1.06 captures typical aerobic fade-out with distance.
Training paces are usually expressed relative to a recent race or a threshold pace. Common zones: easy, marathon, threshold, interval, repetition.
pace = time / distance — min/km or min/mile.t₂ = t₁ × (d₂ / d₁)^1.06 — Race-time prediction.split = pace × segment distance — Even-pace splits.speed = distance / time — km/h or mph.Inputs: 5K in 22:00.
Marathon (42.195 km): t = 22 × (42.195/5)^1.06t ≈ 22 × 9.66 ≈ 212 mint ≈ 3:32:00Result: Predicted marathon ≈ 3 h 32 min, marathon pace ≈ 5:02/km.
Inputs: Pace 4:30/km, distance 5 miles.
4:30/km × 1.60934 ≈ 7:14/mile5 miles → 36:11Result: Pace ≈ 7:14/mile, finish ≈ 36:11.
Pace = time ÷ distance. Convert between km and miles using 1 mile = 1.60934 km.
t₂ = t₁ × (d₂/d₁)^1.06 — a statistical race-time predictor (Riegel 1981).
Within ~3 % when input and target distances are within 3× of each other.
It is your sustainable race pace for 42.195 km, typically 8–12 % slower than 10 K pace.
Yes — use the splits table and assign descending paces to later segments.
They keep training balanced — most volume in easy/marathon, less in threshold and interval.
Yes — pace per km and per mile are shown side by side.
No. It is statistical — execution still depends on training and conditions.
Glycogen depletion, dehydration, and biomechanical fatigue. Riegel's 1.06 captures average fade.
Typical track is 2–3 s/km faster than the same effort on a road race.
Riegel 1981 remains the standard endurance-prediction model.
No — educational only.
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