What is a split?
Runners call the time for one section of a race a split – usually the first and second half. Run both halves at the same speed and you have an even split.
- Negative split: the second half is faster than the first. You start controlled and have something left at the end. Many marathon personal bests are run this way.
- Positive split: the second half is slower. It often happens by accident when you go out too fast – but on a hilly course with a climb late on, a positive split can be the plan.
Use the slider above to set how many percent faster or slower you want to run after the change point. The calculator spreads the time so that you still hit your exact goal. Example: a 4:00:00 marathon with a 2% negative split means a halfway split of 2:01:13 and a second half of 1:58:47.
Slow start
In big races you rarely hit your pace in the crowd after the gun. So plan the first mile or two a little slower on purpose – the calculator makes up the lost time over the rest of the course so your finish time still adds up.
Clock times for spectators
Enter your start time and the table shows the time of day for every split. Family and friends know exactly when to be where to cheer you on – send them your plan with “Copy link”.
Planning fuel and weather
Under “Fueling & weather” you can enter how far apart the aid stations are and how often you want to take a gel. The table and pace band then show you where on the course it's time – no math needed during the race.
Enter the expected temperature and humidity and the calculator adjusts your finish time for the heat. How that works is explained on the heat pace calculator.
What is a pace band?
A pace band is a narrow strip of paper with your planned splits that you carry during the race. At every mile marker you see at a glance whether you're on plan. Click “Print as pace band” and cut the strip out along the dashed line.