🌊 phantomturn

Your watch counted turns that never happened. This puts the numbers back.

🔒 Runs entirely in your browser — the file never leaves this page.

Drop your .fit or .zip here or click to choose one — the .zip from “Export Original” works as it comes, no unpacking

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⚙️ Assumptions

Every default here was calibrated on one swimmer, a Forerunner 265 and a 50 m pool. If your numbers come out wrong, this is where to fix them.

Pool length in metres Leave blank to trust what the watch recorded. Set it if the watch had the wrong pool size — that makes every distance wrong by a fixed ratio and nothing in the data gives it away. Everything else here scales with it.

Lengths per lap button press auto works it out separately for each lap by measuring it against how long one length takes you in this swim — so a session where you lapped every length at first and then swam a continuous block comes out right in both halves. Put a number here instead to force it.

Breaststroke above … strokes per length auto scales it from the pool size — 80 strokes per 100 m, so 40 in a 50 m pool and about 14 in an 18 m one. A fixed number only means anything for one pool size.

… and above … seconds per length A cross-check on the stroke count; auto scales it from the pool too. When the two disagree the lap is reported as ambiguous and the watch's own label is kept.

Reclassify stroke Overrides the watch's stroke classification with the thresholds above.

Trim elapsed time to timer time Drops the gap between stopping the timer and saving. Only applied when the timer was never paused.

🔍 Show the working

Lap	Watch lengths	Fixed lengths	The lengths it saw

Rest laps hold no lengths and are left out, so lap numbers skip where you stopped. Lengths are only ever merged, never split — unless you switch on a split for a possible missed turn, and then only that one, marked as made up. So if the target is wrong for how you actually lapped, the lengths it loses are real, and this table is where that shows.

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