What this calculates
Running pace is the fundamental metric of distance running — the time it takes to cover a set distance, expressed as minutes per kilometre or per mile. Unlike speed, which tells you distance per unit time, pace directly maps to race strategy: if your target is a 45-minute 10K, you need 4:30 min/km. If your GPS shows 5:10 during the race, you know immediately you're 40 seconds per kilometre behind target.
This calculator converts between the three most common pace formats: min/km (used in most of the world), min/mile (used in the United States and UK), and km/h (used on treadmills). It also includes a finish time predictor using the Riegel formula, so you can enter a known race result and see predicted finish times for other standard distances.
The conversion formula is straightforward: 1 mile = 1.60934 kilometres. A pace of 5:00 min/km equals 8:03 min/mile (5:00 × 1.60934 = 8:03). Treadmill speed in km/h is the reciprocal: at 12 km/h you cover 1 km in 5 minutes, so the pace is 5:00 min/km.
For the finish time predictor, this calculator uses the Riegel formula: T₂ = T₁ × (D₂/D₁)^1.06, where T is finish time and D is distance. Enter any known race result and the calculator predicts equivalent times at other standard distances. The 1.06 exponent accounts for the physiological fatigue that makes longer races disproportionately harder. For a full analysis of the formula's accuracy, see the guide to the Riegel formula.
How to use this calculator
Enter your pace in min:ss format per kilometre in the first field. The calculator immediately shows your pace in min/mile and your speed in km/h — no button press needed.
For finish time predictions: enter a recent race result in the second section (format: H:MM:SS for times over an hour, or MM:SS for shorter). Enter the distance in kilometres. The calculator shows predicted finish times for 5K, 10K, half marathon, and full marathon, plus the required pace for each.
If you don't have a recent race time, you can use a time trial: run a measured distance (a flat 5K course or a track session) at full effort and enter that result.
Methodology
Pace conversion uses the exact conversion factor: 1 mile = 1.60934 kilometres (international definition). The finish time predictor uses Riegel's 1981 formula, T₂ = T₁ × (D₂/D₁)^1.06, derived from analysis of race results across distances. The 1.06 exponent was fitted to data from competitive runners; it may slightly overestimate times for recreational runners who fade more at longer distances.
Full methodology and formula sources →
Frequently asked questions
What is a good running pace for a beginner?
A comfortable beginner pace is typically 7:00–9:00 min/km (11:15–14:30 min/mile). You should be able to hold a conversation at this effort — this is often called "conversational pace." Focus on consistency and building time on feet before worrying about speed.
How do I convert min/km to min/mile?
Multiply your min/km pace by 1.60934. For example, 5:00 min/km × 1.60934 = 8:03 min/mile. The calculator handles this automatically as you type.
What pace do I need for a sub-4 hour marathon?
A sub-4 hour marathon requires averaging 5:41 min/km (9:09 min/mile) for 42.195 km. A useful shortcut: your marathon pace in min/km needs to be under 5:41. Enter 4:00:00 for 42.195 km in the finish time predictor to verify.
Why does GPS pace differ from my target pace calculations?
GPS pace readings are smoothed over a window (typically 10–30 seconds) to reduce noise from satellite signal variation. Your instantaneous GPS pace can fluctuate by ±20–30 seconds from your actual effort, especially on turns or under tree cover. Always use rolling average pace for in-race decisions.
How accurate is the Riegel formula for marathon prediction?
For trained runners running a true race effort, the Riegel formula is typically accurate to ±5% for marathon prediction from a half marathon. It's less accurate when the base race was run conservatively, when the runner's training has significantly changed, or when predicting very long distances from very short ones. See the full Riegel formula guide for a detailed accuracy analysis.