Running Tools

Pace converter, race predictor, heart-rate zones, VO₂max estimate and split pacer — no login required.

Pace Converter

Distance

Time

Pace per km5:00 /km

Pace per mile8:03 /mi

Enter distance and finish time to convert pace and estimate standard-distance times.

5K25:00

10K50:00

Half1:45:29

Marathon3:30:59

Race Predictor (Riegel)

Known race distance

Known time

Prefill from my races：

Based on your recent race, predict other distances with the Riegel formula t₂=t₁×(d₂/d₁)^1.06.

5K23:59

10K50:00

Half1:50:19

Marathon3:50:01

Heart-Rate Zone Calculator

Max HRRest HR

Five training zones by heart-rate reserve (HRR, Karvonen method).

Z1 Recovery123–136 bpm

Z2 Aerobic base136–150 bpm

Z3 Aerobic150–163 bpm

Z4 Threshold163–177 bpm

Z5 Anaerobic177–190 bpm

VO₂max / VDOT Estimator

Recent test distance

Recent test time

VO₂max43.5 ml/kg/min

Empirical estimate from the ACSM running equation; for reference only.

Split Pacer (Negative Split)

Target total time

Number of splits (e.g. 1 per km)Negative split % (second half faster)

Generate per-km target pace for a negative-split strategy: second half faster by the set percentage.

14:51/km4:51

24:51/km9:41

34:51/km14:32

44:51/km19:23

54:51/km24:14

64:51/km29:04

74:51/km33:55

84:51/km38:46

94:51/km43:36

104:51/km48:27

114:51/km53:18

124:51/km58:09

134:51/km1:02:59

144:51/km1:07:50

154:51/km1:12:41

164:51/km1:17:32

174:51/km1:22:22

184:51/km1:27:13

194:51/km1:32:04

204:51/km1:36:54

214:51/km1:41:45

224:33/km1:46:18

234:33/km1:50:52

244:33/km1:55:25

254:33/km1:59:58

264:33/km2:04:32

274:33/km2:09:05

284:33/km2:13:38

294:33/km2:18:11

304:33/km2:22:45

314:33/km2:27:18

324:33/km2:31:51

334:33/km2:36:24

344:33/km2:40:58

354:33/km2:45:31

364:33/km2:50:04

374:33/km2:54:38

384:33/km2:59:11

394:33/km3:03:44

404:33/km3:08:17

414:33/km3:12:51

424:33/km3:17:24