Pace calculator
Solve pace, time or distance and read even splits in kilometres or miles. Keep every assumption beside the number.
Pick the unknown
Choose Calculate pace and enter distance plus duration; Calculate time and enter distance plus pace; or Calculate distance and enter duration plus pace. Inactive fields are excluded. Enter hours, minutes and seconds separately. A pace of 5:30 is five minutes thirty seconds.
Distance units are km, mi or m. Pace and split units are km or mi. Switching input units converts the physical quantity. Presets use 5 km, 10 km, 21.0975 km and 42.195 km. Copy saves a plain-text note to the device clipboard; denied permission offers selectable text.
Pace, duration and distance
With distance D in kilometres and duration T in seconds: pace P = T/D seconds per kilometre; duration T = D × P; distance D = T/P. Speed in km/h = 3600/P. One mile equals exactly 1.609344 km, so seconds per mile = P × 1.609344.
The default 10 km in 50:00 gives 5:00/km, 8:03/mi when rounded, and 12 km/h. Calculation values retain precision; clock displays round to whole seconds. Do not multiply rounded displays and expect exact agreement with the original total.
Equal distances and the finish
Each cumulative checkpoint equals its distance times the unrounded average pace. The individual duration is the distance since the previous checkpoint times that pace. A partial finish segment is labeled. These are even splits, not observed laps.
At most 100 complete rows are shown. Longer tables add a finish row and explain that middle rows are omitted; that gap is not labeled as a regular one-unit split. Changing split units changes checkpoint positions, not the physical result.
Race-time scenarios
The optional formula is T2 = T1 × (D2/D1)^k, using consistent distance units. T1 and D1 are the main result; D2 is the selected target. The default exponent is 1.06 and is editable between 1 and 1.2. At k = 1 the relationship is constant pace.
A 25:00 source 5k gives 52:07 for 10 km at k = 1.06, compared with 50:00 at constant pace. The model does not evaluate training, health, course conditions or personal suitability. A primary recreational-runner study reports limitations of simple race-time scaling. This output is a scenario, not a promised result.
Read a result or compare a scenario
Check a previous average, convert a mile pace into kilometre units, or inspect an even finish-time schedule. See the marathon and half marathon guide and 5k pace examples. Match distance to the same timed interval and label elapsed versus moving time.
Bounded arithmetic
Physical distance: 0.001–1000 km. Duration: 1 second–7 days. Hours must be whole 0–168; minutes whole 0–59; seconds 0–59.999. Input pace: whole minutes 0–180 and seconds 0–59.999, totaling at least one second per chosen unit. Computed duration must also stay within the duration bound; computed distance within the distance bound.
Optional target distance uses the same physical range, exponent 1–1.2, and modeled duration must be at most seven days. These are software bounds, not running recommendations. Invalid active inputs hide previous results and disable copying. The calculator keeps fields in browser memory without upload, calculation cookies or history.
Distance conventions and scope
Conventional race presets follow the distances listed in World Athletics terminology. We are independent of event organizers and device providers. The tool does not certify courses, calibrate devices or reproduce timing-service definitions.
Informational arithmetic only. This is not a training, medical or health assessment.
Calculator questions
What can this pace calculator solve?
Choose pace, time or distance as the unknown. Enter the other two quantities, then read equivalent kilometre and mile pace, speed and even-distance splits.
Do the splits describe my actual run?
No. The table applies the calculated average evenly. A final partial segment is labeled, and long tables show an omission note after 100 complete segments.
Is the race-time prediction a guarantee?
No. The optional power-law model uses the stated distance ratio and exponent. It does not assess your preparation, health or race conditions.
Are my inputs uploaded or stored?
No. Calculation fields stay in browser memory. The theme creates no calculation account, upload or persistent history. Copying uses your device clipboard.
What does 5:30 mean?
Five minutes and thirty seconds. This is 5.5 decimal minutes, not 5.30 decimal minutes. Enter the minute and second components separately.
What distances do the race presets use?
5 km, 10 km, 21.0975 km for the half marathon and 42.195 km for the marathon. They convert into your selected distance unit.
Why can the shown splits add to a slightly different total?
Each display is rounded to whole seconds. Cumulative checkpoints and finish time use the unrounded calculation rather than a sum of rounded labels.
Can I compare moving time and elapsed time?
You can calculate each separately. Label the time definition and associated distance; the calculator does not detect pauses or implement another service’s moving-time rule.