PACER
01 · PACE / TIME / DISTANCE — EDIT ANY TWO

RUN THE
NUMBERS.

DISTANCE PRESET
DISTANCE
km
= 6.21 mi
TIME
h:m:s
0.83 hours
PACE· OUTPUT
5:00
/km
8:03 /mi · 12.0 km/h
Computed · TIME ÷ DISTANCE
SPEED12.00 km/h
EQUIV8:03 /mi
1KM SPLIT5:00
02PACE ↔ SPEED
PACE
/km
SPEED
km/h
03SPLITS — 10 KM AT 5:00/km
SPLIT BY
#SPLITPACECUM
015:005:00 /km5:00
025:005:00 /km10:00
035:005:00 /km15:00
045:005:00 /km20:00
055:005:00 /km25:00
065:005:00 /km30:00
075:005:00 /km35:00
085:005:00 /km40:00
095:005:00 /km45:00
105:005:00 /km50:00
04RACE TIMES — FROM A KNOWN RESULT

Enter a recent race you ran. We project to other distances.

SEED DISTANCE
km
SEED TIME
h:m:s
SEED DISTANCE
FATIGUEk = 1.06–1.12
DISTANCEPREDICTEDPACE
1 mi5:573:42 /km
5KSEED20:004:00 /km
10K41:594:12 /km
Half1:34:424:29 /km
Marathon3:28:544:57 /km
50K4:23:395:16 /km
PACER · MADE FOR RUNNERS · NO TRACKING · OPEN-SOURCE MATHv1.0 — RIEGEL · OPENFREEMAP · MINETTI GRADE COST

How to use the marathon pace calculator

Type your goal finish time (e.g. 3:30:00) and the calculator gives you the exact pace — 4:58 /km or 8:00 /mi. Or pin PACE and edit the time; the splits and predictions all update live. No submit button, no reload.

For a smarter race, plan a negative split — running the back half faster than the front. Pick NEG in the Splits section and the table redistributes your target time across each kilometre, with the first split intentionally conservative. The drift slider tunes how aggressive the split is.

Looking for benchmark times? A sub-4 marathon needs 5:41 /km (9:09 /mi). Sub-3:30 needs 4:58 /km (8:00 /mi). A Boston-qualifying 3:00 for most age groups means 4:16 /km (6:52 /mi).

Marathon pace chart

FINISH TIME PACE /KM PACE /MI
2:30 3:33 5:43
3:00 4:16 6:52
3:15 4:37 7:26
3:30 4:58 8:00
3:45 5:20 8:35
4:00 5:41 9:09
4:30 6:24 10:18
5:00 7:06 11:26
Marathon FAQ
What's a good marathon pace?
A "good" pace depends on training, age, and goals. As benchmarks: 4:00 marathon = 5:41 /km (9:09 /mi). 3:30 marathon = 4:58 /km (8:00 /mi). 3:00 marathon = 4:16 /km (6:52 /mi). Boston qualifying times for most age groups land between 3:00 and 4:00.
What's a negative split and why does it matter?
A negative split means running the second half of a race faster than the first half. Research consistently shows it produces faster overall times than positive or even splits, because you stay aerobic longer and have energy when others fade. Most world records — including the marathon — were set with negative splits. Pick "NEG" in the Splits section to plan one.
How accurate is the race time predictor?
It uses the Riegel formula T₂ = T₁ × (D₂ / D₁)^k with the Vickers-Vertosick (2016) distance-dependent exponent — k=1.06 short, climbing through 1.08 (half), 1.10 (marathon), 1.12 (ultras). That fixes Pete Riegel's original fixed-k=1.06 which underestimates marathon fade. Accurate to within ~2% for trained runners on flat courses; less accurate for first-time marathoners or hilly courses (in which case nudge k toward 1.10–1.15 manually). The connected coach goes further — see /coach.
How do I convert min/km to min/mile?
A mile is 1.609344 km, so min/mile = min/km × 1.609344. 5:00 /km = 8:03 /mi. 4:00 /km = 6:26 /mi. 6:00 /km = 9:39 /mi. Toggle KM ↔ MI at the top of the calculator to see your pace in both units instantly.
How do I convert pace to speed?
Pace and speed are reciprocals. Speed (km/h) = 60 ÷ pace (min/km). So 5:00 min/km = 12 km/h. Going the other way, pace (min/km) = 60 ÷ speed (km/h). The PACE ↔ SPEED converter on this page does the math for both units (km/h and mph) live as you type.
Can I share my calculation with someone?
Yes. Every change updates the URL with your full state — distance, time, pace, units, split mode, predictor seed, everything. Copy the URL or hit SHARE to grab a clipboard-ready link. Sending it to a friend opens the calculator with exactly the same numbers you saw.