Running Pace Calculator
Give it two of distance, time and pace and get the rest plus split times
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About this tool
Give it any two of distance, time and pace and the third one appears. There are 5K, 10K, half and full presets, with the half and full using the official distances of 21.0975km and 42.195km. Set a target finish time and you get a split table showing when you should pass each kilometre, plus the speed to dial into a treadmill. One button switches everything between kilometres and miles.
How to use
- Choose what you are solving for: finish time, pace or distance.
- Enter the other two values. The race buttons fill in the exact distance for you.
- Read the table below for the elapsed time at each kilometre.
- To hold back early, switch to negative split and pick how big a swing you want.
Frequently asked questions
- What is a negative split?
- Running the second half faster than the first. Going out too hard on adrenaline usually means falling apart late, whereas starting a touch easy often produces a better overall time. This tool keeps your total the same and spreads the two halves apart by the percentage you choose.
- Why is a half marathon 21.0975km and not 21km?
- Because it is exactly half of the 42.195km marathon. The 100 metres of difference works out to roughly 30 seconds of running, which matters when you are chasing a time barrier.
- How is treadmill speed calculated?
- It is your pace turned upside down into speed. A five-minute kilometre is 12 km/h. Bear in mind that a treadmill belt moves under you with no air resistance, so the same speed feels slightly easier than running outside - a 1% incline is the usual rule of thumb for evening that out.
- My watch measured further than the official race distance.
- That is normal. Courses are certified along the shortest possible line, and in a crowded race nobody runs exactly that line. Your actual path ends up a few hundred metres longer, so it is safer to plan a pace with a little margin over the calculated one.
These are arithmetic figures for a steady effort on flat ground. Hills, wind, heat and late fatigue are not modelled, so real times tend to come out slower. Adjust training intensity to how your body feels. Your input is never sent to a server.