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Swim Time Converter
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Swim Interval & Send-off Calculator

Turn a target pace into a complete set. Enter repeats, distance and pacing, get the repeat time, send-off, total set distance and wall-clock leave times.

Set Builder

Enter repeats, distance and pacing to build your set and find the send-off.

How to Use the Set Builder

  1. 1

    Enter the repeats and distance per repeat, e.g. 8 × 100.

  2. 2

    Set your pace per 100 — your CSS or target race pace works well.

  3. 3

    Either pick a rest per repeat (swim + 15s) or a fixed send-off (on the 1:30) — the calculator fills in the other.

  4. 4

    Read the repeat time, send-off, set totals and a chase-table of wall-clock leave times for the set.

Classic Sets to Try

CSS set: 8–10 × 100 at your CSS pace, 10–15 seconds rest (≈ on a 1:30–1:45 send-off).

Aerobic set: 20 × 50 on a :60 send-off, holding comfortably under :50.

Mid-distance set: 6 × 200 at goal-400 pace on 3:00 send-offs — read around 2:30–2:45.

Ladder/descend: pick a distance with the pace calculator, then run it with send-offs that get tighter as the set progresses.

Find the target pace for any race in the Pace Calculator, then slot it into the set builder above.

Why Use the Swim Interval & Send-off Calculator?

Coaches write sets like "8 × 100 on 1:30" and swimmers nod — then do the mental math at the wall. A swim interval calculator removes the arithmetic: give it repeats, distance and pace, and it produces the send-off, the rest per repeat, the total set distance and a wall-clock table you can follow from the pace clock without thinking.

It is the set builder behind the whole site: take a pace from the Pace Calculator or a CSS pace from the CSS Calculator and turn it into a full training set in three fields.

Send-off math, solved before you dive

"On what send-off do I swim a 1:20 pace with 10 seconds rest?" Leave the wall every 1:30. This calculator does that lookup in both directions — fixed rest or fixed send-off — and rounds to the 5- and 10-second marks you can actually read on the pace clock. That rounding is the difference between a set that runs itself and a set nobody can follow.

Classic swim sets, calculated and repeated

The popular sets — 10 × 100 on 1:30, 20 × 50 on :60, 6 × 200 on 3:00, CSS threshold sets — are all in the quick-start examples. Swimmers asking "what is a good swim set?" get a complete answer: the pace, the send-off and the total distance, so they can slot the set into any practice of any length.

Plan the whole practice, not just one repeat

Sets with chasing send-offs (getting tighter as the set progresses) need a full leave-time table — which is exactly what this builder prints. Combine a couple of sets plus the warm-up in the Calories calculator if you want the practice's total burn, and you have a complete session planned before you reach the deck.

Interval Calculator FAQ

What is a swim send-off?
The send-off is the fixed time interval at which you leave the wall for each repeat. Swim your repeat faster than the send-off, and the leftover time is your rest. For example, 10 × 100 on a 1:30 send-off means leaving every 90 seconds — if each 100 takes 1:20, you get 10 seconds rest per repeat.
Should I build sets around a fixed send-off or a fixed rest?
Both appear in real training. Fixed send-offs (usually rounded to a convenient 1:15, 1:30, 2:00) teach consistent pacing and make a set fit a schedule. Fixed rest (swim + 15 seconds) keeps the work:rest ratio honest as you slow down with fatigue — your rest shrinks as your repeats slow, which is usually the brutal part you want.
What send-off should I pick for a threshold (CSS) set?
A classic CSS set is 8–10 × 100 at your CSS pace with 10–15 seconds rest. Leave the wall every CSS-100 time plus that rest. The calculator rounds up to the nearest 5 or 10 seconds so you can use the pace clock without mental math.
Why do some coaches say "on the :15 or :30"?
On a pace clock, send-offs usually land on a 5- or 15-second mark so swimmers can read them easily (40, 45, 50 on the clock, and so on). That is why the calculator shows your send-off rounded to both 5 and 10 seconds — use a rounding that lands on a mark you can actually follow.
How do I turn a set like 10 × 100 into a full workout plan?
Enter 10 repeats of 100 at your pace per 100, choose a send-off (or a rest such as swim + 15s), and the swim set calculator returns the repeat time, the wall-clock send-off, the total set distance and a chase table of leave times. Work from that table and every rep goes out on time.
What rest should I take between repeats for a speed set?
Speed sets need near-full recovery: 20–30 seconds or more between short repeats. Threshold and CSS sets use tighter rest (10–15 seconds) so the set stays uncomfortable but sustainable. The calculator lets you test both and read the resulting send-off before you touch the water.

More Swimming Tools

Calculators

Course Converters

New here? Start with the Pace Calculator for any race, or read the course conversion guide before comparing times across pools.