Running Split Calculator

Enter your race distance in kilometers, your goal time in minutes and a pacing strategy. The calculator gives the even pace for the goal, the pace for the first and second halves, and the time you should see at halfway.

The negative-split option runs the first half 3% slower than even pace and the second half 3% faster; the positive split does the reverse. Both still add up to your goal time, so you can compare how much each strategy asks of you late in the race.

Paces are shown in decimal minutes, so 5.21 min/km means 5 minutes plus 0.21 of a minute (about 13 seconds), not 5:21. Multiply the decimal part by 60 to get seconds, or use the table below. For mile splits, the running pace calculator converts both ways, and the marathon pace calculator shows the full-distance pace in mm:ss.

Because the two halves are equal distances and the adjustments are equal and opposite (+3% and −3%), the total time always matches your goal. A 3% swing is a modest, commonly coached margin; at 5:00 per km it is a difference of 9 seconds per km either side of even pace. Standard distances: 5 km, 10 km, 21.0975 km (half marathon) and 42.195 km (marathon).

Multiply the decimal part by 60. For example 5.69 min/km → 0.69 × 60 = 41 seconds → 5:41 per km.

• Even split: the most efficient way to run most distances for most runners. Ideal on flat courses in steady weather.
• Negative split: good for half marathons and marathons, especially if you tend to start too fast. Running the first half slightly slower protects glycogen and makes the last third feel controlled.
• Positive split: sometimes unavoidable on courses that are net downhill early or into a headwind late. As a deliberate plan it is risky; most runners who bank time early lose more than they banked.

On hilly courses, pace by effort and expect your splits to vary with the terrain even if the effort is even.

Note your target time at each 5 km mat before the race, or write the halfway time on your hand. If you reach halfway more than about 1% ahead of the plan (around a minute in a 2-hour half), ease off — early gains rarely hold. To check whether your goal time is realistic in the first place, run a recent race through the race time predictor.