Calculate running pace, time, or distance — enter any two to find the third. Predicts race finish times for 5K, 10K, half marathon, and marathon. Includes pace zones by effort level and pace per mile/km toggle.
Enter two of the three values: pace (min/km or min/mile), total time (hh:mm:ss), or distance (km or miles). Leave the third blank and it will be calculated automatically.
Switch between km and miles with the unit toggle. Your result (pace, time, or distance) is displayed prominently. The calculator also converts between min/km and min/mile.
Based on your current pace, race time predictions are shown for 5K, 10K, half marathon (21.1 km), and marathon (42.2 km). A pace zone guide shows your effort level relative to common training zones.
Pace (min/km) = Total time (minutes) ÷ Distance (km). Example: Running 10 km in 55 minutes gives a pace of 5:30 per km. To find time: Time = Pace × Distance. To find distance: Distance = Time ÷ Pace. To convert between min/km and min/mile: multiply min/km by 1.60934 to get min/mile; divide min/mile by 1.60934 to get min/km.
Pace benchmarks vary widely by age and fitness: Beginner: 7–9 min/km (11–15 min/mile). Recreational runner: 5:30–7:00 min/km. Intermediate: 4:30–5:30 min/km. Advanced: 3:45–4:30 min/km. Elite amateur: 3:00–3:45 min/km. Professional/competitive: under 3:00 min/km. A "good" pace is relative to your current fitness — consistency and gradual progression matter more than hitting specific times.
Riegel's formula: T₂ = T₁ × (D₂/D₁)^1.06, where T is time and D is distance. A 25-minute 5K predicts roughly a 3:55–4:10 marathon, accounting for the fatigue factor (exponent 1.06). Alternatively, multiply your 5K time by 9.0–9.5 to estimate marathon time. These predictions assume comparable fitness, pacing strategy, and race conditions.
Zone 1 (Easy/Recovery): 60–70% max HR, very conversational, sustainable indefinitely. Zone 2 (Aerobic/Base): 70–80% max HR, can speak in sentences, builds aerobic base. Zone 3 (Tempo): 80–87% max HR, comfortably hard, 20–60 min sustainable. Zone 4 (Threshold): 87–92% max HR, only a few words, 10–30 min max. Zone 5 (VO2 Max): 92–97% max HR, cannot speak, 3–8 min maximum.
A negative split is running the second half of a race faster than the first half. It is considered optimal race strategy because it prevents early glycogen depletion, maintains form, and allows a strong finish. Elite marathoners typically run the second half 1–2 minutes faster than the first. Starting 5–10 seconds per km slower than goal pace in the first half is the most common recommendation for longer races.
To convert pace per km to pace per mile: multiply by 1.60934. Example: 5:00/km × 1.60934 = 8:03/mile. To convert min/mile to min/km: divide by 1.60934. Example: 8:00/mile ÷ 1.60934 = 4:58/km. This calculator handles the conversion automatically — just toggle the unit switch between km and miles.
