Race Pace Calculator
Works both ways: enter a goal finish time to get the pace you need, or enter a pace to see the finish time it adds up to.
How this calculator works
The math is simple division — pace is just your finish time spread across the distance:
- Pace per km = finish time ÷ distance in kilometers
- Pace per mile = finish time ÷ distance in miles (1 mile = 1.609344 km)
Race distances use their official measurements, not rounded ones: a half marathon is 21.0975 km (13.11 mi) and a marathon is 42.195 km (26.22 mi). Those decimals matter — treating a marathon as a flat 26 miles would put your goal pace off by about 5 seconds per mile, which is roughly two minutes across the race.
One practical note: this gives you an average. Real races have hills, aid stations, and crowded first miles. Use the number as your target, not a metronome.
FAQ
What pace do I need for a sub-4-hour marathon?
About 9:09/mi (5:41/km) held for the full 26.2 miles. Most runners aim a few seconds per mile faster than the exact figure to build in a buffer — a bathroom stop or a slow water station shouldn't cost you the goal.
Why does my GPS say I ran farther than the race distance?
Courses are measured along the shortest legal route. Swing wide around corners or weave through a crowd and you'll cover more ground than the official distance — so your watch pace reads slower than your actual race pace. Running the tangents is how you stop paying for extra metres.
Should I run even splits?
For most people, yes — even effort, which usually means even or slightly negative splits. Starting faster than goal pace is the classic way to blow up, and the marathon punishes it hardest. Bank fitness, not time.