Turn your phone into a personal rep counter. Pick squats, push-ups, jumping jacks or chair stands, prop your phone 2–3 metres away, and an on-device AI watches your form, counts every rep out loud and saves your personal best. Your video never leaves your device.
How the AI rep counter works
When you tap Start camera, the page loads Google’s open-source MediaPipe Pose Landmarker, a version of the BlazePose model. It finds 33 points on your body (shoulders, elbows, wrists, hips, knees, ankles and more) many times per second, directly in your browser. From those points the counter works out your joint angles, smooths out the jitter, and counts a rep only when you move through both the bottom and the top of the movement. A buffer between the two positions stops small wobbles from being counted twice.
Joint angles are measured the simple way: 180° is a straight leg or arm, and the number gets smaller the more you bend.
| Exercise | A rep counts when | Best camera position |
|---|---|---|
| Squat | Knees bend to about 110° or less, then you stand back up (knees straighter than 150°). “Great depth” means about 95° or less. | 2–3 m away, turned 45° or side-on, whole body in view |
| Push-up | Elbows bend to about 100° or less, then straighten past 145° with your body roughly horizontal. “Full range” means about 90° or less. | Phone on the floor about 2 m away, side-on |
| Jumping jack | Hands go above your shoulders and feet go wider than about 1.3 times shoulder width, then both come back together. | 2.5–3 m away, facing the phone |
| Chair stand | You go from seated to fully upright (knees and hips straighter than 150°). | 2–3 m away, side-on or at 45° |
These cut-offs are our own counting rules, chosen to be fair rather than strict. They are not a clinical standard. If the counter misses a rep, use the +1 and −1 buttons.
Tips for an accurate count
- Get your whole body in the frame. Prop the phone at about hip height, 2–3 metres away. Portrait works well for squats and jumping jacks, landscape for push-ups.
- Turn side-on for squats and push-ups. The AI judges bending most reliably from the side or at 45°.
- Use good light and wear clothes that contrast with the background. Baggy clothes can hide your knees and elbows.
- Keep other people out of view. The counter follows one person.
- Tap the full-screen button so the count is easy to read from a distance, and turn on Count out loud so you do not need to look.
Try the 30-second chair stand
Choose Chair stand, then Timed challenge and 30 s. This is the 30-second chair stand test, a simple measure of leg strength and endurance developed by Jones, Rikli and Beam. Use a sturdy chair without arms (about 43 cm or 17 inches high) with its back against a wall, cross your arms over your chest, and stand up fully and sit down as many times as you can in 30 seconds.
The test was designed for adults aged 60 and over. In the CDC’s STEADI version, fewer than 14 stands is below average for men aged 60–64 and fewer than 12 for women of that age. There is no official standard for people in their 30s, 40s or 50s, so use your first score as your personal baseline and retest every month or two.
Why push-ups and squats are worth tracking after 35
The World Health Organization recommends muscle-strengthening activity that works all major muscle groups on 2 or more days a week, on top of aerobic exercise. Bodyweight squats and push-ups are an easy way to do that at home, and counting reps shows you are getting stronger.
In a 10-year study of 1,104 active male firefighters (average age about 40), men who could do more than 40 push-ups at the start had 96% fewer cardiovascular events than men who managed fewer than 10. It was an observational study in fit, working men, so it shows a link, not cause and effect, and it may not apply to women or less active men. Treat your push-up count as a fitness marker, not a heart test.
Safety first
- Stop straight away if you feel pain, chest pain or pressure, dizziness, or unusual shortness of breath. Seek urgent medical help if chest pain does not settle with rest.
- Check with your doctor before hard or timed efforts if you have a heart condition, high blood pressure that is not under control, recent surgery, a joint injury, or you have not exercised for a long time.
- Clear the space around you, put your phone somewhere it cannot fall, and use a chair that will not slide.
- Quality beats speed. Stop the set when your form breaks down.
Your privacy
Everything happens on your device. Your camera images go straight from the camera into the AI model running in your browser and are never uploaded, saved or recorded. The page downloads the MediaPipe library from jsDelivr and the pose model file from Google’s servers, the same way a page downloads a font or an image. Your personal best is kept only in your own browser, and the share card includes only the exercise, reps and time.
Sources
- Google AI Edge: MediaPipe Pose Landmarker guide (33 body landmarks, model variants)
- Bazarevsky V, Grishchenko I, Raveendran K, et al. (2020). BlazePose: on-device real-time body pose tracking. arXiv:2006.10204
- Google: Model card, BlazePose GHUM 3D
- Jones CJ, Rikli RE, Beam WC (1999). A 30-s chair-stand test as a measure of lower body strength in community-residing older adults. Research Quarterly for Exercise and Sport, 70(2), 113–119
- CDC STEADI: Assessment, 30-Second Chair Stand
- Yang J, Christophi CA, Farioli A, et al. (2019). Association between push-up exercise capacity and future cardiovascular events among active adult men. JAMA Network Open, 2(2), e188341
- World Health Organization (2020). Guidelines on physical activity and sedentary behaviour
This tool is for general fitness and education, not medical advice, and it is not a medical device. Rep counts are estimates and can be wrong. Check with your doctor before starting a new exercise plan, especially if you have a heart condition, high blood pressure, an injury or another health condition.
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