Split times: your km-by-km table for your race
This split time calculator gives your cumulative time at every kilometer or mile to hit your goal. You can run at an even pace, or choose a negative split: a percentage gap from your average pace between the two halves, with the second half faster.
Fill in the fields to see the result.
How to use it
- Choose the distance (5K, 10K, half, marathon) and the unit: km or miles.
- Enter your goal time.
- If you want to finish faster, set the gap between the two halves as a percentage (0% = even pace).
- Write down your key splits or copy the table onto a wristband.
The method
The calculation starts from your average pace: your goal time divided by the distance. With no gap, every kilometer is run at that pace. With a gap of E%, the first half is run at the average pace plus E/2%, the second at the average pace minus E/2%. Your finish time stays exactly on your goal.
Why not start fast to “bank time”? Studies on pacing strategies (Abbiss and Laursen, 2008) show that in long events, spreading the effort evenly works better. An analysis of 1.7 million recreational marathon runners (Smyth, 2018) shows that starting too fast costs you a much slower finish. In marathon world records, the best runners hold a very steady pace, with little variation (Díaz et al., 2018).
An example
Half marathon goal of 1:45:00, so 4:59 per km on average. At an even pace, you reach km 5 in 24:53, km 10 in 49:46 and km 20 in 1:39:32. With a 2% gap, your first half is run at 5:02 per km and the second at 4:56: you reach km 10 in 50:16, halfway in 53:02, and you finish the second half in 51:59. In miles, your first split comes at 8:05.
Limitations
The table assumes a flat course and steady conditions. A hill, wind, heat or a crowded start shift your splits without you actually being behind. On a hilly course, think in terms of effort rather than pace. And an unrealistic goal gives splits you can't hold: check your goal against a recent race first.
Frequently asked questions
What is a negative split?
It means running the second half of the race faster than the first. It keeps you from burning out early and lets you finish strong.
What gap should you choose between the two halves?
A small gap is enough: 1 to 2% in this calculator. Beyond that, you risk starting too slowly and never making up the lost time.
Should you run at an even pace in a marathon?
It's the safest strategy for most runners. Recent world records show a very steady pace from start to finish.
Why does my watch show more distance than the race?
GPS isn't perfect and you don't always take the shortest line. Go by the official kilometer markers for your splits.
Sources
- Abbiss, C. R. and Laursen, P. B. (2008). Describing and understanding pacing strategies during athletic competition. Sports Medicine, 38(3), 239-252.
- Smyth, B. (2018). Fast starters and slow finishers: A large-scale data analysis of pacing at the beginning and end of the marathon for recreational runners. Journal of Sports Analytics.
- Díaz, J. J., Fernández-Ozcorta, E. J. and Santos-Concejero, J. (2018). The influence of pacing strategy on marathon world records. European Journal of Sport Science, 18(6), 781-786.
What if ELYO worked it out for you?
ELYO reads your workouts and sees the pace you really hold in training. It adjusts your plan so your race goal matches your real fitness.