Running Pace Calculator
Work out your pace per mile and per km, or your finish time, and see splits for common race distances.
This runs entirely in your browser. Nothing you type is uploaded anywhere.
How to use this tool
This running pace calculator works two ways. In "Find my pace" mode, pick a race distance (or enter a custom one), type your target time as hours, minutes and seconds, and the tool returns your required pace per mile and per kilometer. In "Find my finish time" mode, enter the pace you plan to hold, choose whether it is per mile or per km, and the tool returns your projected finish time. In both modes you get a splits table showing the pace and the elapsed time at common race distances, so you can plan a race target time at a glance.
The formula behind the splits
finish time = pace per unit × distance in that unit
1 mile = 1.609344 km
Pace is simply your total time divided by the distance covered, expressed as minutes and seconds per mile or per kilometer. To convert a per-kilometer pace into a per-mile pace you multiply it by 1.609344, because one mile is that many kilometers. To estimate the elapsed time at any split, the calculator multiplies your pace by the distance of that split. This is the same math used for marathon, half marathon, 10K and 5K pace planning.
A real example
Suppose you want to run a marathon (42.195 km) in 4 hours and 0 minutes. That is 14,400 seconds over 42.195 km, which is about 5:41 per kilometer. Multiplying by 1.609344 gives roughly 9:09 per mile. The splits table would then show you passing the 10K mark at about 56:53, the half marathon at about 2 hours flat, and the 30K mark at about 2 hours 50 minutes, which helps you avoid starting too fast and fading late.
Common questions
What is the difference between pace and speed?
Pace is the time it takes to cover one unit of distance, such as 9 minutes per mile, and is the standard way runners describe effort. Speed is the reverse, the distance covered per unit of time, such as 6.7 miles per hour. This tool uses pace because it is easier to hold a steady pace on the watch during a race.
How do I convert pace per mile to pace per km?
Divide your per-mile pace by 1.609344 to get the per-kilometer pace, since one mile equals that many kilometers. Going the other way, multiply your per-kilometer pace by 1.609344. The calculator does both conversions automatically and shows each result in the table.
What pace do I need for a sub-4-hour marathon?
A marathon is 26.2 miles, so a 4-hour finish needs about 9:09 per mile, or roughly 5:41 per kilometer. Switch to "Find my pace" mode, choose Marathon, and enter 4 hours to see the exact splits and confirm the 5K, 10K and half marathon checkpoints.
Why are my real race splits slower than the table?
The splits table assumes an even, steady pace across the whole distance. Real races involve hills, fatigue, weather, fueling and crowded starts, so most runners slow down in the later miles. Use the table as a target pacing guide rather than a guarantee, and plan to bank a little energy early.
Can I use this for a custom distance like an 8K?
Yes. Choose "Custom distance" in the distance menu, type the distance, and pick whether it is in miles or kilometers. The calculator will compute your pace or finish time for that exact distance and still show the standard 5K, 10K, half marathon and marathon rows for comparison.
This calculator gives estimates for general training and planning. It is not medical or coaching advice. Check with a qualified professional before starting a new training or racing program.