Swim Interval Sendoff Calculator
Calculate swim sendoff times from repeat distance, pace per 100, target rest, and repeat count, with total set time and pacing notes.
Why this calculator is useful for swimmers
A sendoff is the clock time at which each repeat starts. If a swimmer is doing 10 × 100 on 2:00, every repeat starts two minutes after the previous one, and the remaining time after finishing becomes rest. This calculator helps build sendoffs from actual pace instead of guessing.
Formula and calculation method
The calculator estimates swim time from the selected repeat distance and pace per 100. It then adds the target rest to produce a sendoff and multiplies by the number of repeats to estimate total set time.
How to use the result in real swim training
Use sendoff planning for aerobic sets, threshold sets, CSS work, sprint sessions, and masters workouts. If you want consistent technique, choose a sendoff that allows enough rest to hold form. If the goal is endurance stress, use a tighter sendoff that still allows you to complete the set without falling apart.
Important context and trusted references
For race and pool context, this page treats pool length carefully because official pool standards distinguish 50 m long-course pools and 25 m short-course pools; the World Aquatics facilities rules describe those standard competition pool lengths and measurement tolerances. For efficiency metrics, Garmin's swim terminology page explains SWOLF and critical swim speed terminology. Research also connects swim velocity with stroke rate and distance per stroke; a classic PubMed-indexed paper on stroke rate, distance per stroke, and swimming velocity is useful background when interpreting stroke metrics.
Common mistakes to avoid
Do not choose a sendoff based only on ego. If the first two repeats feel easy but the last five collapse, the sendoff may be too aggressive for the goal. Also remember that a sendoff includes swim time and rest together; it is not the same thing as rest time.
Frequently asked questions
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It is mainly designed for pool swimming because most swim pace, lap-count, split, SWOLF, and sendoff calculations depend on a known pool length. You can still use the distance-based calculators for open-water estimates, but open water adds variables such as current, sighting, wetsuit use, drafting, turns, and GPS accuracy. For precise training comparisons, use the same course or the same pool length whenever possible.
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Use the same unit your pool or race uses. A 25-yard pool and a 25-meter pool are not the same distance, so pace and lap counts can differ enough to matter. The calculators include both units because swimmers often compare short-course yards, short-course meters, and long-course meters. If you are tracking progress, consistency is more important than the unit itself.
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Swim watches estimate lengths, strokes, pace, and rest using sensors and pool-length settings. If the pool length is wrong, if a turn is missed, or if a drill set does not produce normal stroke motion, the watch can produce a different pace or distance than a manual calculation. Manual calculators are useful for planning sets and checking results, while watch data is useful for recording actual sessions.
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Beginners should use these numbers as feedback rather than as strict judgment. A slower pace with relaxed breathing and good form is often more useful than forcing a fast pace with poor technique. Track one or two metrics at a time, such as pace per 100 m and stroke count per length, then watch how they change across several weeks.
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No calculator can see your body position, catch, kick timing, breathing rhythm, or fatigue pattern. These tools are best for planning and analysis. They can help you understand pace, splits, stroke rate, distance per stroke, CSS, SWOLF, and sendoff timing, but technical feedback from a coach or video analysis can still be much more valuable for improving form.