Setting Custom Plate Diameters for Accurate Velocity Tracking
How to set the exact diameter of your plates so velocity readings stay accurate when you're not training on standard plates.
Metric measures bar speed by tracking how far your plates move between video frames, then converting that to real-world distance using the plate’s diameter as the reference. By default, Metric is set for standard 45cm (17 inch) Olympic lifting/bumper plates, however you can customise this value before you record.
For most gyms, and most lifters you will never have to touch this plate size setting as all your lifts are done with standard bumper/olympic weight plates. If you’re training with non-standard plates, or using a custom tracking disc for non-barbell exercises, you need to adjust the plate size before starting your recording otherwise data will be inaccurate.
Tip: Metric only cares about the largest diameter plate on the bar, since that’s what it tracks. If you’re lifting with two 20kg plates and a 5kg change plate outside that, the 20s are what matters — set the size for those.
When to set a custom plate size
Set a custom size if any of the following are true for the plates you’re using:
- Fractional / change plates only — These range from 15–30cm. If a fractional plate is the largest plate on the bar, use its size.
- Tri-grip weight plates — Some brands of weight plate, most commonly the rubber-coated trip grip style plates have 20kg plates that are slightly below the regulation 45cm diameter.
- Non-Olympic gym plates — standard 1-inch hole plates often come in non-standard diameters.
If you’re unsure, measure the full diameter across the face of the largest plate on the bar with a tape measure or a measuring app on your phone. Round to the nearest centimetre.
Setting a custom plate size
- Open the recording screen for the lift you’re about to do.
- Tap the recording settings icon near the top of the screen.
- Toggle off default plate size and enter your plate diameter in centimetres.
- Confirm. This plate size setting persists for all sets unless you change it back.
Plate detection preview
Before you start recording, the preview shows a green ring on the plate Metric expects to track. Use this to confirm the right plate is being picked up.
Note: The preview can bounce between the bigger and smaller plates of your barbell as you adjust framing. This is purely cosmetic and the small plate is ignored once tracking starts, set your plate size to the largest plate on the bar regardless of which ring is highlighted in preview. Once the bar starts moving, Metric tracks the largest moving plate.