SWOLF Calculator - Swim Efficiency Score by Length

Calculate a SWOLF score for one pool length or average a complete interval while keeping pool length and stroke-count convention explicit.

How the SWOLF Calculator Works

SWOLF combines elapsed seconds and a consistently recorded stroke or stroke-cycle count. For one length, add the two values. For a multi-length interval, add the swimming-time and recorded-count totals and divide by completed lengths. Exclude rest time when comparing with a swim-only device score. Enter a positive time as seconds, M:SS or H:MM:SS, with optional fractional seconds. Colon seconds must be below 60, and colon minutes must be below 60 when hours are present. Leading minutes or hours are not capped at 24 hours; the parsed time and derived results must remain finite. Recorded counts may be zero but must be nonnegative whole numbers; completed lengths must be positive whole numbers. Counts and length counts are limited to safely representable integers, at most 9,007,199,254,740,991.

Result	Calculation	Best use
Single-length SWOLF	Length seconds + recorded count	Quick repeat comparison in one pool
Average interval SWOLF	(Total seconds + total count) / lengths	Smoothing variation across a set
Distance	Pool length × completed lengths	Confirming the interval entered

How to compare scores

Keep the pool length, stroke, equipment, and counting method the same. A lower value can reflect less time, fewer recorded strokes, or both, but it does not by itself explain why a swim changed.

Garmin Swim 2 counts a stroke when the arm wearing the watch completes a full cycle. Other device or manual methods can differ. Select the convention matching your recorded data; this calculator uses the entered count without halving or doubling it. Avoid mixing individual arm entries, complete cycles and device-reported counts.

Example

An eight-length interval completed in 240 seconds with 120 recorded counts averages 30 seconds and 15 counts per length. The average SWOLF is 45.

Sources

Sources: Garmin Swim 2 owner’s manual, Swim Terminology (length, interval, watch-arm stroke count and SWOLF) and Data Fields (average interval SWOLF and swim time excluding rest); accessed October 23, 2026. The interval calculation is the arithmetic mean from totals covering the same completed lengths, before display rounding; it does not reproduce undocumented device rounding or count-detection behavior.