Running Pace & Race Time Predictor
Calculate your running pace, finish time, or required distance. Predict race times for 5K, 10K, half marathon, and marathon.
EmbedNot needed for Race Time Predictor mode
e.g. 5.5 = 5 min 30 sec per km
e.g. 55 = 55 minutes | 90 = 1 hour 30 min
For Race Time Predictor only
Your recent finishing time in minutes
How to Use This Calculator
This calculator has three modes — pick the one that matches what you need.
Mode 1: Finish Time
Know your target pace and race distance? Enter both to calculate your expected finish time. Enter pace as a decimal: 5 min 30 sec = 5.5, 6 min 45 sec = 6.75.Mode 2: Pace
Completed a run and want to know your pace? Enter your total time in minutes and the distance covered. The calculator returns your pace per km and equivalent speed in km/h.Mode 3: Race Time Predictor
Enter a recent race result and predict equivalent performances at other standard distances. Based on the Riegel formula (T₂ = T₁ × (D₂/D₁)^1.06), which models the relationship between fatigue and distance for endurance runners.Common Pace Benchmarks
Tips for Pacing a Race
Start 5–10 seconds per km slower than your goal pace for the first 2 km — running too hard early is the most common reason for blowing up in the second half. Aim for even splits or a slight negative split (second half faster than first).
Formula
Riegel Formula: T₂ = T₁ × (D₂/D₁)^1.06 | Pace = Time / DistanceFrequently Asked Questions
How accurate is the race time predictor?
The Riegel formula is accurate to within 1–5% for most runners predicting across similar distances (e.g. 5K to 10K). Predictions become less reliable when extrapolating far beyond your reference race — a 5K to marathon prediction assumes a level of endurance training that may not match reality.
What is a good 5K time?
Under 30 minutes is a solid recreational goal. Under 25 minutes is competitive. Sub-20 minutes puts you in the top 10% of parkrun finishers. Elite runners go under 15 minutes.
What is a good marathon pace?
For a first marathon, finishing under 5 hours (about 7:06/km) is a common goal. Sub-4 hours (5:41/km) is a popular milestone for experienced runners. Sub-3 hours (4:16/km) is elite amateur territory.
How do I enter pace in decimal format?
Enter minutes as a decimal. 5 minutes 30 seconds = 5.5. 6 minutes 45 seconds = 6.75. The formula is: minutes + (seconds ÷ 60).
What is a negative split?
Running the second half of a race faster than the first half. It is the most efficient pacing strategy for distance events — starting conservatively preserves glycogen and delays fatigue, allowing you to accelerate when others are slowing down.
Should I use km or miles?
This calculator uses kilometres. To convert: 1 mile = 1.609 km. A 5:00/km pace equals approximately 8:03/mile. A 6:00/min/mile pace equals approximately 3:44/km.
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