An app that counts squat reps — automatically
Yes, your phone camera can count squat reps automatically: prop it side-on, and pose tracking reads your knee angle every frame — each descent past a depth threshold and return to standing is one rep. Done well it's more reliable than wrist-based counting for barbell lifts (a wearable can't see your legs), and a good counter doesn't just count: it scores each rep so you know which ones were actually deep.
How camera rep counting works
The phone runs a body-pose model on the live camera feed and computes your knee-flexion angle frame by frame. A hysteresis state machine — standing → descending → bottom → ascending — registers a rep only when you pass genuine depth and return to standing, which filters out half-reps, walkouts and re-racks.
Because the model runs on-device (Apple's Vision framework), counting is instant and the video never leaves the phone.
Why not just count in your head — or with a watch?
Everyone loses count under a heavy bar; effort eats attention. Wrist wearables are worse for squats — your arm barely moves, so they routinely miscount leg work. The camera sees the actual movement that defines the rep.
The bigger win is what counting unlocks: if the app knows rep 4 happened and how deep it was, it can score the set, speak the count out loud, auto-run your rest timer, and decide next session's weight — a rep counter becomes a coach.
Counting is the floor, scoring is the point
Spotter counts every squat rep and scores each one on depth and tempo the moment it lands. Hit your prescribed reps with good depth and it adds 2.5 kg next session; miss and it holds or deloads. The count you can't keep in your head becomes the progression you don't have to plan.
Answers
Can my iPhone count squat reps automatically?
Yes — with the phone propped side-on, on-device pose tracking reads your knee angle and counts each full descent-and-return as a rep, live, with no wearable needed.
Do fitness watches count squats accurately?
Not reliably. Wrist-based sensors infer reps from arm motion, and in a squat your arms barely move — the camera sees the legs, which is where the rep actually happens.
Does Spotter count reps for lifts other than the squat?
The squat is camera-counted and scored today. Bench, row, press and deadlift are logged with one tap and still auto-progress their own working weights; camera scoring for more lifts is on the roadmap.
Related: AI squat form app · Spotter vs StrongLifts · How Spotter works