Interval / Lap Timer

An interval timer built for workouts — set work and rest durations plus a round count, and it cycles through automatically with a beep at every transition.

Interval training exists because of a fairly counterintuitive fact about the human body: shorter bursts of harder effort, separated by planned rest, tend to build more capacity than the same total time spent at a steady, moderate pace. That's true whether you're talking about sprinting, weightlifting circuits, or even structured study sessions — the "work hard, then genuinely rest" pattern outperforms "grind continuously" in a lot of contexts, which is exactly why interval timers exist as their own category separate from a plain countdown.

The mechanical difference from a regular countdown timer is that an interval timer alternates automatically between two states — work and rest — for a set number of rounds, without you having to restart anything in between. That automation matters more than it sounds like it should: in the middle of an actual workout, fumbling with a phone to restart a timer between rounds breaks the rhythm that makes interval training effective in the first place. The whole point is to be able to put the device down, hear the transitions, and stay in the effort.

This version lets you set your own work duration, rest duration, and number of rounds, so it works whether you're doing a quick five-round sprint session or a longer structured circuit. A distinct sound marks each transition between work and rest, so you always know which phase you're in without needing to look.

1. Set your work time, rest time, and number of rounds.
2. Press Start to begin round 1.
3. Listen for the beep at each work/rest transition.
4. The timer stops automatically after your final round.