What work and rest split should I start with?

Thirty seconds on and thirty seconds off is a fair first setting for most people. Once the work stops feeling hard by the last round, cut the rest to fifteen or twenty seconds rather than adding rounds.

Will the screen stay awake while the timer runs?

The timer asks your browser to hold the screen on for the length of the session. Locking the phone by hand or switching to another app still stops the audio cues, so leave the tab in front.

Do I need an account?

No. The clock runs inside the page, nothing is stored and nothing is sent anywhere.

How many rounds make a session?

Ten rounds of thirty on and thirty off is ten minutes on the clock, half of it working. Most conditioning sessions land between eight and twenty rounds.

Timer

Interval timer

A work and rest clock you set yourself. Choose the seconds on, the seconds off and the number of rounds, then run it fullscreen.

The timer

Work

Rest

Rounds

Lead-in

The clock runs fullscreen and keeps the screen awake. It needs JavaScript, so with scripting off the plan below is the whole session written out.

Total: 9:40
Working: 5:00
Periods: 20

01ReadyGet ready0:10
02WorkWork0:30
03RestRest0:30
04WorkWork0:30
05RestRest0:30
06WorkWork0:30
07RestRest0:30
08WorkWork0:30
09RestRest0:30
10WorkWork0:30
11RestRest0:30
12WorkWork0:30
13RestRest0:30
14WorkWork0:30
15RestRest0:30
16WorkWork0:30
17RestRest0:30
18WorkWork0:30
19RestRest0:30
20WorkWork0:30

How it works

An interval timer counts a fixed period of work, then a fixed period of rest, and repeats both until the rounds run out. That is the whole job. Setting the two numbers yourself is what separates it from a protocol timer, and it is why the same clock covers rowing intervals, kettlebell work and a run on a hill.

Set the work seconds, the rest seconds and the round count, then press start. The clock runs fullscreen with a beep for the last three seconds of every period, so you never have to look at it. Arrow keys move between periods and the space bar pauses.

Ten rounds of forty seconds on and twenty off is a common conditioning session: twenty minutes of clock, thirteen of it working. Ten rounds of twenty on and forty off is the same total length and a completely different session, because the long rest lets you go far harder in each burst.

The ratio between work and rest is the setting that decides what you are training. Rest longer than the work and you are training how hard you can go. Rest shorter than the work and you are training how long you can keep going while tired. Neither is better, and running the same ratio every session is how conditioning stalls.

One warning about very short rests. Below about ten seconds there is no recovery at all, so the work periods get slower and slower and the session turns into a slow grind at a fixed effort. If that happens, either add rest or cut the number of rounds.

Questions

What work and rest split should I start with?: Thirty seconds on and thirty seconds off is a fair first setting for most people. Once the work stops feeling hard by the last round, cut the rest to fifteen or twenty seconds rather than adding rounds.
Will the screen stay awake while the timer runs?: The timer asks your browser to hold the screen on for the length of the session. Locking the phone by hand or switching to another app still stops the audio cues, so leave the tab in front.
Do I need an account?: No. The clock runs inside the page, nothing is stored and nothing is sent anywhere.
How many rounds make a session?: Ten rounds of thirty on and thirty off is ten minutes on the clock, half of it working. Most conditioning sessions land between eight and twenty rounds.