Running split calculator

Choose a race, a goal time and how you want to spread the effort. Get every split, then print it as a pace band.

Race

Goal time

Splits every

Second half vs first: even

Halfway target1:52:30second half 1:52:30 · difference 0:00

How the effort is spread

Each bar is one kilometre; taller means slower. The total is the same whatever split you choose — drag the slider above and watch the bars tilt.

Marathon · 3:45:00 · even

Km	Split	Elapsed
1	5:20	5:20
2	5:20	10:40
3	5:20	16:00
4	5:20	21:20
5	5:20	26:40
6	5:20	32:00
7	5:20	37:20
8	5:20	42:40
9	5:20	47:59
10	5:20	53:19
11	5:20	58:39
12	5:20	1:03:59
13	5:20	1:09:19
14	5:20	1:14:39
15	5:20	1:19:59
16	5:20	1:25:19
17	5:20	1:30:39
18	5:20	1:35:59
19	5:20	1:41:19
20	5:20	1:46:39
21	5:20	1:51:59
22	5:20	1:57:19
23	5:20	2:02:39
24	5:20	2:07:59
25	5:20	2:13:19
26	5:20	2:18:39
27	5:20	2:23:58
28	5:20	2:29:18
29	5:20	2:34:38
30	5:20	2:39:58
31	5:20	2:45:18
32	5:20	2:50:38
33	5:20	2:55:58
34	5:20	3:01:18
35	5:20	3:06:38
36	5:20	3:11:58
37	5:20	3:17:18
38	5:20	3:22:38
39	5:20	3:27:58
40	5:20	3:33:18
41	5:20	3:38:38
42	5:20	3:43:58
Marathon	5:20	3:45:00

Why even beats fast-then-hang-on

Energy cost rises faster than speed, so time banked early costs more than it saves. Going 2% too fast for the first half of a marathon and 4% slower for the second half loses time overall, and the late slowdown is usually worse than planned. Studies of big-city marathon results consistently find most amateurs slow in the second half — and the ones who hold pace finish closer to their predicted times.

Build the goal from evidence first: the race time predictor gives a realistic target, and the marathon pace chart shows it next to neighbouring goals.

Questions runners ask

What is a negative split?

Running the second half of a race faster than the first. Almost every men’s and women’s marathon world record of the last few decades has been run with even or slightly negative splits.

How much of a negative split should I plan?

Small: 1–2% for a marathon (about 1–3 minutes difference between halves for most runners) and up to 3% for shorter races. A bigger planned negative split usually means the first half was needlessly slow.

What is a pace band?

A strip listing the elapsed time you should see at each mile or kilometre marker, worn around the wrist. Print this page, cut out the band and tape it with clear tape so it survives sweat and water stations.

What is a split in running?

The time for a section of a race — each kilometre, mile or lap — or the elapsed time at that point. Checking splits tells you whether you are on pace long before the finish clock does.

Running split calculator

How the effort is spread

Marathon · 3:45:00 · even

Why even beats fast-then-hang-on

Questions runners ask

Every calculator