This calculator requires times from a 100/500 or 200/800 swim test performed as a single back-to-back effort with 1 minute of recovery between the two distances.

• Short distance (100 or 200): Swim as fast as possible — this is an all-out sprint effort from a push start.
• Rest 1 minute, then immediately begin the longer distance.
• Long distance (500 or 800): Swim at the fastest pace you can sustain for the full distance — hard but controlled.

Accurate test times are essential for reliable pace zones. Long-course athletes (70.3 / Ironman) are encouraged to use the 200/800 test for better race-specific data, while short-course athletes may prefer the 100/500.

Count your strokes (optional): During each test swim, count your strokes on every length. Count each time a hand enters the water. Add them up and divide by the number of lengths to get your average strokes per length (SPL) for the short and the long swim. Enter both to get stroke count feedback on top of your pace zones, or leave both blank to skip it. Count per length of whatever pool you tested in and set the pool length in the additional pool data section.

Racing open water? Open the Open Water Predictions and Planning section to turn your pool test into a predicted race swim time, adjusted for your experience, the conditions, your sighting and navigation, and whether you wear a wetsuit.

New to swimming? If you know your short distance time but haven't yet completed the full test, use the ⚡ Estimate button next to the longer distance field. It will calculate an approximate time based on your short distance multiplied out and adding 25%. This is a starting point — completing the full test will always give you more accurate pace zones.