Health & Fitness
Running Pace Calculator
Solve for pace, time, or distance: fill any two and get the third, with splits, race presets, and heat and altitude correction.
How it works
Behind the numbers
Pace is time divided by distance, but in practice you rarely have all three numbers. Enter any two (a distance with a finish time, or a target pace with a race distance) and the calculator solves for the third. Switch between miles and kilometers at any time; the distance converts and everything recalculates.
The splits table breaks your run into even mile or kilometer chunks at the solved pace, so you know what each split should read on your watch. The race buttons fill in standard distances (5K, 10K, half marathon, marathon) with the exact course lengths.
The environment section adjusts your pace for heat and altitude. The heat estimate follows U.S. coach Mark Hadley's rule of thumb: about 0.125% slower for each degree Fahrenheit above 60°F, with a 5–10°F bump added for high humidity (via Canadian Running Magazine). The altitude estimate slows pace about 3% per 1,000 meters of elevation, from a 2026 MDPI Sensors study of distance-running effort, consistent with the altitude tables in Daniels' Running Formula. Both are planning estimates, not medical advice.
FAQ
Questions, answered
How do you calculate running pace?
Divide your finish time by the distance. A 50-minute 10K (6.21 miles) is 50 ÷ 6.21, about 8:03 per mile. This calculator does the same math in reverse too: give it any two of pace, time, and distance and it solves for the third.
What pace do I need for a sub-2-hour half marathon?
A half marathon is 13.11 miles, so 120 minutes ÷ 13.11 gives about 9:09 per mile. Tap the half-marathon preset, enter 2:00:00 as the time, and the calculator solves the pace. Then check the splits table for even pacing.
How much does heat slow down running pace?
A common rule of thumb from coach Mark Hadley is about 0.125% slower for each degree Fahrenheit above 60°F, with extra allowance for humidity. At 85°F with high humidity that works out to roughly 3–4% slower, about 15–20 seconds per mile on an 8:00 pace.
Does altitude affect running pace?
Yes. Research on distance-running effort (MDPI Sensors, 2026) finds pace slows roughly 3% per 1,000 meters of elevation, consistent with the altitude tables in Daniels' Running Formula. At 5,000 feet that is a little under 5%, about 22 seconds per mile on an 8:00 pace.