What is a negative split?

Running the second half of a race faster than the first. For example, a 4:00:00 marathon run as 2:02:20 + 1:57:40 is a 4:40 negative split — the second half was 4 minutes and 40 seconds quicker than the first. The percentage expresses the same gap: 2% means the second half was run 2% faster per mile than the even-split pace.

What percentage negative split should I aim for?

2–3% is the right target for most runners — the Conservative preset. It gives enough cushion to absorb bad weather or a slightly hot first mile without sacrificing finish time. Experienced athletes with several marathons under their belt can push 4–5% (Moderate/Aggressive), but going beyond 6% leaves too much margin at halfway and can backfire if the second half is harder than expected (wind, heat, course profile).

Is negative splitting better than even splitting?

For most distance runners, yes — particularly at the marathon distance and beyond. Running the first half slightly slower conserves glycogen, keeps lactate low, and preserves running form late in the race. A RunRepeat analysis of 2019 NYC and Boston marathons found that over 70% of personal-best finishes were run with a negative split. At 5K and 10K, the margin narrows — even splits are often just as effective because fuelling is not a limiter.

What is a positive split?

The opposite of a negative split — running the first half faster than the second. Positive splits are almost always unintentional and almost always produce a slower finish than the runner was fit for. Santos-Lozano et al. (2014) found average positive splits of 15.6% in men and 11.7% in women across 2 million marathon finishers; faster finishers positive-split less, pointing to pacing discipline rather than physiology as the differentiator.

How do I practice negative splitting?

Build it into your long runs. A classic session: run the first 80% of your long run at easy pace, then the final 2–3 miles at marathon goal pace or slightly faster. Over a 12-week block, six or seven of these progression long runs hard-code the physical and mental skill of finishing fast. Short progression workouts (e.g., 6 × 1 mi with each rep 5 s/mi faster) reinforce the same pattern midweek.

Do elite runners negative split?

Many of the fastest marathon performances in history were negative splits. Eliud Kipchoge's 2018 Berlin Marathon (2:01:39) was 1:01:06 / 1:00:33 — a small but clean negative. Kelvin Kiptum's 2023 Chicago world record was a substantial negative. In championship racing, negative splits are near-universal: the pack eases the first half to stay together, then the race starts in the final 10K.

What if I can't hold the faster second-half pace?

It means the split percentage was too aggressive for the day — cut it back 1–2 percentage points next time. The failure is not the negative-split strategy itself; the failure is overestimating how much faster the second half can realistically be. A modest 2% negative split finished on plan almost always beats an ambitious 5% negative split that collapses into a positive split by mile 22.

Negative Split Calculator

Calculate first-half and second-half paces for a negative split, with conservative to aggressive presets and a progression table.

Race Distance

Goal Time

Split Preset

Split percentage

How much faster (%) to run the second half. 2% is conservative; 5%+ is aggressive.

First Half Pace

9:20/mi

(5:48 /km)

Second Half Pace

8:58/mi

5:34 /km

First Half Time

2:02:24

Second Half Time

1:57:35

Half Difference

−4:48

Progressive Splits

Split Progression

Mile-by-mile pace progression for your race.

#	Distance	Split Time	Cumulative	Pace
1	1 km	5:48	0:05:48	5:48
2	2 km	5:48	0:11:36	5:48
3	3 km	5:48	0:17:24	5:48
4	4 km	5:48	0:23:12	5:48
5	5 km	5:48	0:29:00	5:48
6	6 km	5:48	0:34:48	5:48
7	7 km	5:48	0:40:36	5:48
8	8 km	5:48	0:46:24	5:48
9	9 km	5:48	0:52:12	5:48
10	10 km	5:48	0:58:00	5:48
11	11 km	5:48	1:03:49	5:48
12	12 km	5:48	1:09:37	5:48
13	13 km	5:48	1:15:25	5:48
14	14 km	5:48	1:21:13	5:48
15	15 km	5:48	1:27:01	5:48
16	16 km	5:48	1:32:49	5:48
17	17 km	5:48	1:38:37	5:48
18	18 km	5:48	1:44:25	5:48
19	19 km	5:48	1:50:13	5:48
20	20 km	5:48	1:56:01	5:48
21	21 km	5:48	2:01:50	5:48
22	22 km	5:34	2:07:24	5:34
23	23 km	5:34	2:12:58	5:34
24	24 km	5:34	2:18:33	5:34
25	25 km	5:34	2:24:07	5:34
26	26 km	5:34	2:29:42	5:34
27	27 km	5:34	2:35:16	5:34
28	28 km	5:34	2:40:51	5:34
29	29 km	5:34	2:46:25	5:34
30	30 km	5:34	2:52:00	5:34
31	31 km	5:34	2:57:34	5:34
32	32 km	5:34	3:03:08	5:34
33	33 km	5:34	3:08:43	5:34
34	34 km	5:34	3:14:17	5:34
35	35 km	5:34	3:19:52	5:34
36	36 km	5:34	3:25:26	5:34
37	37 km	5:34	3:31:01	5:34
38	38 km	5:34	3:36:35	5:34
39	39 km	5:34	3:42:10	5:34
40	40 km	5:34	3:47:44	5:34
41	41 km	5:34	3:53:19	5:34
42	42 km	5:34	3:58:53	5:34
43	42.195 km	1:06	4:00:00	5:41

Calculate first-half and second-half paces for a negative split race strategy, with mile-by-mile progression and the exact time savings from strategic pacing. Enter your race distance (10K, half, marathon, 50K, or custom), your goal finish time, and a split percentage between 0.5% and 10% — or pick a preset (Conservative 2%, Moderate 4%, Aggressive 6%). The calculator returns your first-half pace, your second-half pace (that percentage faster), per-half finish times, the exact gap between halves, and a full progression table in step or gradual mode. Negative splits are the most reliable way to run a personal best in any race longer than 10K — they save glycogen, keep form, and let you pass runners late.

first_half_pace = even_pace × (1 + pct/100)    ·    second_half_pace = even_pace × (1 − pct/100)

even_pace: = Goal time ÷ distance — the constant pace needed for an even split
pct: = Split percentage — how much faster (%) the second half should be relative to even pace
first_half_pace: = Slower pace held for the first half of the race
second_half_pace: = Faster pace held for the second half — the pct figure faster than even

Worked example — 4:00:00 marathon with a 2% negative split

even_pace = 4:00:00 ÷ 26.2 mi = 9:09 /mi (5:41 /km)
pct = 2
first_half_pace = 9:09 × 1.02 = 9:20 /mi (5:48 /km)
second_half_pace= 9:09 × 0.98 = 8:58 /mi (5:34 /km)
first half time = 9:20 × 13.1 = 2:02:20
second half time= 8:58 × 13.1 = 1:57:40
total = 4:00:00 ✓ · gap = 4:40
= 2% negative split: 9:20 /mi → 8:58 /mi · second half 4:40 faster than the first

Formula F12 from site/03-globals.md §formulas. The +pct / −pct symmetry is first-order — tiny second-order drift (<2 seconds on a marathon) falls within round-off tolerance for all practical split presets.

Marathon pacing for a 2% negative split — first-half pace starts 2% slower than even and the second half finishes 2% faster. Paces in /mi (metric equivalents in the conversion table below).
Goal time	Even pace	2% first half	2% second half	Gap
2:30:00	5:43	5:50	5:36	1:50
2:45:00	6:17	6:25	6:10	2:02
3:00:00	6:52	7:00	6:44	2:12
3:15:00	7:26	7:35	7:17	2:24
3:30:00	8:01	8:10	7:51	2:34
3:45:00	8:35	8:45	8:25	2:46
4:00:00	9:09	9:20	8:58	2:56
4:15:00	9:44	9:56	9:32	3:08
4:30:00	10:18	10:30	10:06	3:18
4:45:00	10:53	11:05	10:40	3:30
5:00:00	11:27	11:40	11:14	3:40
5:30:00	12:36	12:51	12:21	4:04

PR rate — NYC Marathon 2019

70%negative splits

Share of personal-best finishers who ran a negative split (RunRepeat, n=19,614)

Time penalty — 5% positive split

4–6min slower

Typical loss on a marathon vs. a runner of identical fitness who runs even or negative

Glycogen depletion at 20 mi

−15–20%lower

Runners on a controlled first-half pace have more stored carbs at mile 20 than positive-splitters

Perceived effort — first half

RPE 6–7of 10

Should feel controlled; if RPE hits 8 before halfway, the first-half pace is too aggressive

Last-5K pace vs. first-5K

−1.5–3%faster

Real-world elite marathon pattern: Kipchoge, Kipruto, Jepchirchir all negative-split at record attempts

Passing position — last 10K

+50–200places

Typical mass-marathon experience for a conservative 2% negative-splitter vs. the field average

Executing a Negative Split

Running the math is easy; holding back for 13.1 miles is the hard part. Five practical steps that turn a negative-split plan into a negative-split race.

Lock in the first-half pace before the gun
Write the first-half pace on your wrist, program your watch workout, or tattoo it on your hand — whatever keeps a single number in front of you at mile 1. Starting-line adrenaline is the single biggest cause of blown splits; the first mile is often 15–30 s/mi faster than intended unless you've pre-committed to a hard number.
Run the first 5K 5–10 seconds per mile slower than goal pace
Even runners targeting a 2% negative split should open deliberately slow — that extra cushion absorbs crowd jostling, GPS error, and the early-race tendency to drift fast. Check pace at mile 1 and mile 3; if you're ahead, slow down. Lost seconds in the first 5K are cheap; seconds spent in the red before halfway are expensive.
Hit halfway within 5 seconds of your target
The split percentage collapses to noise if you arrive at halfway off-plan. Use the mile-by-mile progression table (expandable panel above) as a waypoint system. If you're 10+ seconds fast at halfway, hold current pace — do not accelerate further. If you're 10+ seconds slow, start gradual acceleration now rather than waiting for mile 20.
Increase pace in the second half by 3–5 s/mi every 3–4 miles
A gradual drop is kinder than a step change. Practically: miles 14–16 at even pace, 17–19 five seconds/mi faster, 20–22 ten seconds/mi faster, then race the last 5K. The step-mode progression table is a planning tool; in execution, think in 3- to 4-mile blocks.
Save the last 5K for racing, not surviving
A successful negative split feels like passing people in the last 5K — not like running scared. If you're fighting to hold the even-pace number at mile 23, the split percentage was too aggressive. Dial it back 1–2 percentage points next cycle. Over a 12-week marathon block, two or three workouts ending with a 2-mile pickup at goal pace hard-code the skill of finishing fast.

Two pacing strategies for goal-time races

Even splits

Same pace from start to finish; lowest cognitive load in execution
Mathematically optimal when glycogen lasts the full distance — which it usually does not beyond 25 km for most amateurs
Best for: time-trial efforts, flat parkruns, 5K and 10K races
Risk: a hot first mile can push pace 5–10 s/mi faster than planned and silently become a positive split
Used by: world-record marathon attempts on paced courses (Kipchoge Berlin 2018, 1:01:06 / 1:01:33 — functionally even with a tiny negative)

Reliable when fitness, conditions, and fuelling are dialled in

Negative splits

Second half 1.5–5% faster than the first; cognitive load: higher, requires discipline to hold back early
Best for: marathons, halfs, and trail/ultra races where glycogen, cumulative fatigue, or heat are in play
Risk: start too slow and the second-half pace becomes unrealistic — aim for 2–3% for most runners
Used by: 70%+ of marathon PRs at NYC and Boston 2019 (RunRepeat); common in championship marathons where podium position depends on a closing surge
Particularly valuable for first marathons and return-to-racing blocks where execution is a bigger unknown than fitness

The safer strategy when in doubt — it builds in a buffer against heat, wind, and bad early mile splits

Explore More Running Tools

Race Split Calculator

Generate full split tables for even, positive, and negative strategies across any distance.

Marathon Pace Calculator

Goal-time marathon pacing with mile- and kilometre-by-kilometre splits.

Half Marathon Pace Calculator

Per-mile and per-km splits for goal-time half marathons — the distance where negative splits pay off most reliably.

Race Pace Calculator

Goal-time pace tables for every standard race distance from 5K to marathon.

Training Pace Calculator

VDOT-based easy, marathon, threshold, and interval paces — the paces that make a negative split sustainable.

Sources

1.Negative-split pacing (F12) — PaceSplit methodology — PaceSplit Methodology (accessed 2026-04-22)
2.Santos-Lozano, A. et al. — Influence of sex and level on marathon pacing strategy: Insights from the New York City race — International Journal of Sports Medicine, 35(11), 933–938, 2014 (accessed 2026-04-22)
3.RunRepeat — Marathon Pacing Statistics (NYC + Boston, n=19,614) — RunRepeat, 2019 (accessed 2026-04-22)
4.Eliud Kipchoge — Berlin Marathon 2018 (2:01:39, halves 1:01:06 / 1:00:33) — BMW Berlin Marathon Official Results, 2018 (accessed 2026-04-22)

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