TimerPlanHow long is this interval session?
Interval sessions are written as 40 on, 20 off, eight rounds — three numbers that decide a fourth nobody works out until they are already sweating.
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How this works
Session shapes that already have names
Common interval blocks, and what the whole thing costs in wall-clock time once the rest is counted.
| Work | Rest | Rounds | Whole block | Known as |
|---|---|---|---|---|
| 20s | 10s | 8 | 4:00 | Tabata |
| 30s | 30s | 10 | 10:00 | Even intervals |
| 40s | 20s | 8 | 8:00 | Class round |
| 45s | 15s | 8 | 8:00 | Eight-station circuit |
| 60s | 60s | 8 | 16:00 | Rowing or running repeats |
| 3m | 1m | 3 | 12:00 | Boxing rounds |
The total is always longer than the work — at 2:1 the rest is a third of the session, which is where lunch breaks overrun.
Frequently asked questions
What work-to-rest ratio should I use?
It depends what the interval is training. Around 1:1 — 40 on, 20 off is close — keeps the heart rate high and suits conditioning. Longer rest, 1:2 or 1:3, lets each effort be genuinely maximal and suits speed work. Very short rest, 2:1 and beyond, is muscular endurance and is where form goes first.
Why is the total longer than I expect?
Because rest counts. Eight rounds of 40 on and 20 off is eight minutes, not five and a half — the rest is a third of the session. Sessions written as “twenty minutes of intervals” almost always mean twenty minutes including rest, and that is what this total gives you.
Can I run the session from a timer?
Set each block on the timer as you reach it, or use the classroom timer full screen where a group has to see it. A plan is the sheet; the timer is the thing that counts. Keeping them separate is deliberate — a plan that has to run in real time is a plan you cannot look at while you exercise.