Running tools
Do the math, then head out
Pace, split and track calculations run locally in the browser. Every tool publishes its formula, rounding and independent examples.
Pace and splits
Pace calculator: distance, time, pace and speed
Choose any two of distance, time and pace to solve the third, with pace per kilometre, pace per mile and average speed shown together. A road-running arithmetic tool that does not model hills, stops or wind.
Open tool 1.0.0Race time prediction: the Riegel formula and its 1.06 exponent
Use one known road race result to estimate the finish time and pace at another distance from 5 km to the marathon under the Riegel model. An empirical estimate, not a promise.
Open tool 1.0.0Run-walk planner: cycles or total duration
Plan run-walk intervals. Enter a run and walk duration, then lay out the intervals by number of cycles or by total time, marking any truncated final segment. Time arithmetic only; no distance, pace or fitness estimate.
Open tool 1.1.0Split table: break a target time into segments
Enter total distance, total time and split distance, then choose an even or negative-split strategy to build a printable table. The final segment may be short, and all whole seconds add up exactly to the total.
Open toolTrack files
Files are read in this browser only and are never uploaded; processing runs in a Worker.
Route comparison: distance, elevation basis and technicality across published versions
Compare two to four published route versions field by field: distance, elevation basis, surface and technicality. Missing values stay unknown, and no safety or difficulty ranking is generated.
Open tool 1.0.0Track conversion: GPX and GeoJSON lines
Convert a GPX or GeoJSON line to the other format in your browser, preserving coordinate order and available elevation while stripping times, devices, names and original metadata.
Open tool 1.0.0Track simplification: projected tolerance, point and distance comparison
Simplify each segment independently with a local metric projection and iterative RDP, keeping endpoints and segment breaks while reporting the change in points and WGS84 distance. The original file is never modified.
Open tool 1.0.0Track viewer: read your GPX and GeoJSON
Inspect a track's point count, start and end, distance and available elevation locally in your browser, without uploading the file. Missing elevation is shown as unknown, never filled with zero.
Open toolThe tools do not send distances, durations or track files to a server. Empirical models state their limits; results are not training, medical or safety guarantees.
Further planned tools join once their formula, sources and independent examples are complete. Empty shells are not published. Formula and sources are listed on each tool page.