GPX Pace Calculator

How the GPX Pace Calculator works

GPX pace calculator: distance, time and splits

A GPX file from a watch or phone is a list of points with a position, usually an elevation, and a timestamp. Everything a running or cycling app tells you about a workout is derived from that list, and this tool does the same arithmetic in your browser without uploading the file anywhere.

Distance is the sum of the straight-line distances between consecutive points, using the haversine formula on the WGS84 sphere. Watches sample every second or every few metres, so the result is within a fraction of a percent of what the device reported. A route exported from a planning site with only a few hundred points will read slightly short on bendy roads, since corners are cut.

Elapsed versus moving time. Elapsed time is first timestamp to last. Moving time drops every interval where you were travelling under 0.5 metres per second — stopped at lights, waiting at a gate, fiddling with the watch — which is roughly how Strava and Garmin define it, though each uses its own threshold. Average pace is shown for both, and the moving figure is the one that matches what a watch shows as you run.

Splits. The time at each whole kilometre or mile is interpolated between the two points either side of it, so a split is accurate to within one sample. A final partial split appears when the remainder is more than a couple of percent of a unit, with its pace scaled up to a full unit. The elevation column is the net change over that split, and the CSV download has the same rows for a spreadsheet.

Routes without times. KML and GeoJSON exports, and GPX files from planners like Komoot or Ride with GPS, usually have no timestamps. Enter a target pace such as 5:30 and the tool projects a finish time and even splits at that pace, which is handy for pacing a race or estimating how long a planned walk will take. The map tiles are from OpenStreetMap; the file itself never leaves your computer.

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