Pace Calculator

How it works

Pace is time divided by distance. Finish time is distance multiplied by pace, and distance is time divided by pace after bringing both quantities into consistent units. The calculator uses exact rational decimal-distance and unit boundaries internally, with clock inputs in integer milliseconds; reported numeric values are rounded browser numbers. A kilometre is 1000 metres; one international mile is exactly 1609.344 metres. Speed in kilometres per hour and miles per hour is the inverse view of the same supplied or computed pace. Changing a unit changes how the number is interpreted; it does not silently convert your typed entry into a different value. Review the unit beside each field.

Choose the quantity to calculate before entering the other two. In Pace mode, supply distance and elapsed time. In Finish time mode, supply distance and pace per kilometre or mile. In Distance mode, supply elapsed time and pace. The derived result is reported in kilometres alongside both pace units and both speed units. Starter example values are labelled and excluded from workflow measurement until you edit the inputs. Reset example restores the initial 5 km / 25-minute example. Clear empties the fields and removes the previous result.

Clock text has two explicit forms: M:SS and H:MM:SS. Thus 1:30 is one minute thirty seconds, while 1:30:00 is one hour thirty minutes. Seconds may contain up to three decimal places; 25:00.125 includes 125 milliseconds. A minutes or seconds field after a colon must have two digits from 00 to 59. Bare decimal minutes such as 5.5 are rejected to avoid confusing minutes with seconds. Decimal-point distance values and scientific notation are accepted within the shared browser-number validation rules. There is no location lookup, GPS track, route upload or account requirement.

Supported distance is 1 metre through 1,000 kilometres. Supplied or computed time must be positive and no more than 1000 hours; computed pace per kilometre and per mile must each remain from 1 millisecond through 1000 hours. Invalid, zero, negative, nonfinite, underflowed or out-of-range values reject the calculation instead of producing Infinity or a misleading plan. The split table is limited to 1000 intervals. These are software bounds, not recommendations about physical exercise.

Kilometre splits place a boundary every 1000 metres; mile splits place one every 1609.344 metres. The final boundary is always the total distance, including a shorter final interval. A split's cumulative elapsed time is total time multiplied by the fraction of total distance completed. Cumulative times are rounded to the nearest millisecond, then each interval duration is the difference from the previous rounded cumulative time. Therefore the interval durations add to the rounded finish time; independently rounding a repeated pace and multiplying it is not used. The final interval is explicitly marked partial when it is shorter than the chosen unit. Boundary counts use exact decimal-distance and unit ratios, so an exact whole-mile distance cannot create an extra microscopic interval. A genuinely tiny partial interval is retained: when its rounded interval time is zero milliseconds, the display says <0.001 s and the exports retain its positive unrounded duration and a sub-millisecond flag.

The on-page table previews the first 30 intervals, while CSV and JSON retain every supported interval. CSV includes cumulative and interval distance, rounded numeric millisecond times, readable clock times, the positive unrounded interval duration, and partial / sub-millisecond flags. JSON also retains the source settings and unrounded computed values. Displayed clocks are rounded to milliseconds; speed and distance labels use a limited number of significant digits. Browser binary64 arithmetic is approximate and does not make entered decimal distances exact. A mathematical constant-pace plan cannot establish a person's sustainable pace or a real-world finish prediction.

The calculation and downloads stay in the current browser tab; your distances and times are not sent to a route or exercise service, stored in history or put into the page URL. Changing any input or setting removes stale results and exports. Optional anonymous measurement records one explicit calculation and its outcome, plus a result-download action, without distances, times or location. Downloaded files contain the values you deliberately retain, and remain wherever your browser saves them.

Common use cases

• Work out pace per kilometre and per mile from a known distance and elapsed time.
• Calculate a constant-pace finish time for an explicitly chosen distance.
• Prepare kilometre or mile splits that retain the final partial interval.
• Download a checkable split schedule instead of repeatedly converting rounded clock labels.

Frequently asked questions

Standards and limitations

• NIST: international-mile conversion factor
• World Athletics: the 42.195 km marathon distance