3 different things get called a gym timer app, they solve different problems, and most complaints about them come from having installed the wrong one.
A rest timer counts down the gap between sets of a lift. An interval timer runs a fixed work and rest pattern for a set number of rounds. A circuit timer does the same but names what you are doing in each round. Pick by the job, not by the ratings.
The 3 timers, in one table
| Rest timer | Interval timer | Circuit timer | |
|---|---|---|---|
| What you type | One duration | Work, rest, rounds | Work, rest, and a list of movements |
| Starts when | You finish a set | You start the session | You start the session |
| Runs unattended | No, one countdown at a time | Yes, to the end | Yes, to the end |
| Tells you what to do | No | No | Yes, the next station |
| Typical use | Heavy squats, bench, deadlift | Tabata, HIIT, bag rounds | 4-station circuit, 2 times through |
| Fails when | You forget to start it | The structure changes mid-session | The movements do not divide evenly into rounds |
The mismatch that annoys people most: using an interval timer as a rest timer. Interval timers assume the clock is in charge, and a lifter is not on a clock between sets. They are ready when they are ready. Using a rest timer for circuits is the same mistake mirrored, and it means touching the phone 20 times in a session with chalk on your hands.
The rest timer, and the drift nobody notices
Rest between sets is the one part of a training session almost everybody measures badly. It starts at 90 seconds. 6 sets in, it is 3 minutes, because a set got hard and then somebody talked to you.
That drift matters differently depending on what you are doing. For heavy strength work, long rest is correct and the timer is only there to stop it running to 5 minutes when you meant 3. For hypertrophy work at 60 to 90 seconds, the drift is the difference between the stimulus you planned and a considerably easier session.
What a rest timer needs is small: one duration, a big start button, and a cue you can hear with the phone in a pocket. What it must not need is your attention, because the reason it exists is that your attention is on the next set.
The interval timer
Once the clock is in charge, the requirements change completely. You are now going to be mid-effort at every transition, which means the timer has to work without being looked at, and it has to keep the right time while you are nowhere near it.
Both of those are harder than they sound on iPhone. The system suspends an app within about 5 seconds of the screen locking, and a timer built on a ticking counter simply stops. Wake the phone 2 minutes later and it resumes from where it froze, handing you rest you did not earn. That is the single most common defect in the category, and it is invisible in an App Store listing.
The timers that survive never count. They record the instant you started, expand the session into a list of phases, and answer every question by subtracting one time from another. Nothing to fall behind, because nothing is being kept.
The other half is audio: a distinct tone into work and into rest, a count-in before the change so you can finish the rep rather than be interrupted by it, and ducking your music instead of stopping it.
The circuit timer
A circuit is an interval session where the rounds are not the same as each other. 4 stations with 40 seconds each and 20 seconds to move, 2 times through. What makes it a circuit is that round 3 is not round 1, and a timer that only counts rounds cannot help you with that.
The requirement it adds is a name on every work interval. That sounds cosmetic until you are on station 3 of 4 with a heart rate of 170, at which point “what am I supposed to be doing” is a real and frequent question. Getting the answer from a Lock Screen, without picking the phone up, is the difference between a circuit that runs and one that stops every round.
The arithmetic is where circuit timers differ most. 4 movements over 8 rounds is 2 times through. 4 movements over 6 rounds is 1 and a half, which is either an error or exactly what you meant, and it is worth knowing which one your app assumes.
The 30-20-10 structure is the same problem in miniature: 30 seconds easy with 20 moderate and 10 flat out, which is 3 phases in a minute rather than 2. An interval timer with a work field and a rest field cannot express it at all.
What breaks in a gym, specifically
All the requirements above are ordinary. These 4 are what the room adds.
It is loud. Cues have to survive plates, fans and somebody’s speaker. This is the case for a wrist haptic as a backup, and against any timer whose only signal is visual.
The phone is not in your hand. It is face down on a bench, on the floor, or in a pocket. Everything the timer wants to tell you has to arrive as sound, as a Lock Screen glance, or not at all.
Your hands are unusable. Chalk, gloves, a bar, or just being out of breath. Any interaction that needs opening a phone is an interaction that will not happen.
Sessions get interrupted. Somebody wants the rack. A timer that cannot pause and resume without losing its place turns a 2-minute interruption into a restarted session.
Choosing without installing 5 apps
- Only ever rest between heavy sets? A rest timer, or the stock Clock app, and stop reading.
- Fixed work and rest, same every round? An interval timer, judged on the locked-screen test.
- Different movement each round? A circuit timer, and check what it does when the movements do not divide evenly.
- Both, in the same session? An interval timer that lets you name movements, which is the overlap where most people live.
Whichever you pick, the 7 criteria that separate the good ones are worth running through before you pay for anything.
The Rounds setup for the gym
Rounds is the second and third of those three. Type the work seconds, the rest seconds, the rounds and the sets, name a movement per round if it is a circuit, and press start. The round, the phase, the seconds left and the next movement live on the Lock Screen and in the Dynamic Island, with pause and skip as buttons there, so a set that gets interrupted does not become a session that gets restarted.
It does not keep a rest timer for heavy singles and it is not a training log. The timing engine holds no counter of any kind, which is why a session that spent 10 minutes in a pocket comes back on the right round.
Rounds is in open beta through TestFlight. Before you trust any gym timer, run the same test on it: start a session, lock the phone, wait 2 minutes, and see whether it comes back where the clock says it should be.
Common questions
Can I set up an interval timer on my phone?
Yes, and on iPhone you have 3 routes. The stock Clock app runs one countdown at a time with no repeats, so you restart it by hand at every change. Shortcuts can chain countdowns and is fiddly to change. A dedicated interval timer app is where you type the work seconds, the rest seconds and the round count once and press start. Only the third one survives a session where your hands are busy.
What is a good app for keeping track of workouts?
That is a different app from a timer, and mixing the two is why so many are bloated. A training log records what you lifted and how it changed over months. A timer runs the clock during the session. Some apps do both adequately and neither well. Decide which job is the one that fails you today, because the timer job is the one that has to work with your hands occupied.
What is the 30-20-10 rule for HIIT training?
A minute broken into 30 seconds easy with 20 seconds moderate and 10 seconds all-out, usually repeated 5 times for a 5-minute block. It came out of running research and it works as a conditioning finisher on a bike or a rower. As a timer requirement it is a 3-phase interval rather than a 2-phase version, which some interval timers cannot express at all.
How long should I rest between sets?
For heavy strength work, 2 to 5 minutes, and the long end is not laziness. For hypertrophy work, 60 to 90 seconds. For conditioning circuits, whatever the structure says. The reason a rest timer earns its place is that unmeasured rest drifts upward across a session, and by the last set you are often taking twice what you took on the first without noticing.
Is there a free gym timer app?
Plenty, and free takes 3 shapes: ad-supported, a paid app with a limited free tier, and free tools with no business model behind them. The one to avoid in a gym is ad-supported, because the ad appears at the interval change, which is the one moment you needed the screen to be a timer.
Does a gym timer keep running when the screen locks?
The well-built ones do, and a surprising number do not. iOS suspends an app within seconds of the screen locking, so a timer that counts seconds as they pass freezes and comes back late. Test it before you rely on it: start a session, lock the phone for 2 minutes, and check whether the round it shows matches a wall clock.