Swim Interval & Set Builder
Set your reps, distance, target pace, and rest, and the builder returns the swim time per rep, the total distance and time, and a send-off interval rounded to the pace clock.
Turning a pace into a workout
Interval sets are the backbone of pool training: repeated efforts at a target pace with measured rest, so you can hold speed longer than you could in one continuous swim. The arithmetic — swim time per repeat, rest, send-off, and total — is easy to get wrong in your head on the pool deck. This builder does it instantly, so you can write a set that fits the time you have and the pace you want to hold.
Find your target pace first with the Swim Pace Calculator, and check the set’s total against a round figure using the Distance & Lap Counter.
Frequently Asked Questions
What is a send-off interval?
The send-off is the time you leave on for each repeat — swim plus rest combined. On a set of 10 × 100 on 1:50, you push off every 1:50: if a repeat takes 1:30 you get 20 seconds' rest, and if you swim 1:35 you only get 15. The tool adds your target swim time to your chosen rest and rounds up to the next five seconds, the way a pace clock is read.
How is the total set time worked out?
It multiplies your target pace by the per-rep distance to get the swim time for one repeat, multiplies that by the number of reps for total swimming, and adds the rest taken between reps — that is the rest for every repeat except the last, since you stop at the wall on the final one. Swim time plus rest time gives the total the set should take.
Should I set rest by seconds or by a send-off time?
Both are common. Fixed rest — say 20 seconds between each — keeps the recovery constant regardless of speed and suits technique or endurance work. A fixed send-off keeps the whole interval constant, so swimming faster earns more rest, which builds race discipline. This builder takes a rest value and then shows you the send-off it implies, so you can plan either way.
How do I make a set harder or easier?
Tighten the send-off by cutting the rest, and the same swim becomes a tougher aerobic effort with less recovery. Lengthen the rest and you can hold a faster pace on each repeat for speed work. Changing reps or distance scales the total volume. Adjust one variable at a time and watch how the total set time and rest respond.
A planning estimate. Send-offs assume you hold the target pace — adjust rest to your real fitness and how you feel on the day.