Fitness trackers and smart rings
Tracker and Ring Runtime
The one wrist category where a listing will commit to a week, and the reason it can.
A full turn is 30 days
- WHOOP 5.0 with 12-Month Membership14 days
- RingConn Gen 2 Air, Size 910 days
- OURA Ring 4, Size 88 days
- Google Fitbit Air Special Edition7 days
- Stated range
- 7 to 14 days
- Listings with a figure
- 4 of 7
Every figure on this page is the manufacturer’s own stated number, produced under conditions the manufacturer chose and usually does not describe. Nothing here was measured by this site.
What the figure measures
A figure in days on a tracker is a duty-cycle claim. The device is asleep most of the time, waking to sample a sensor and to talk to a radio, and the manufacturer has calculated how long a cell lasts at that rhythm.
The rhythm is the whole number. A screenless band and a ring have almost no display cost, so the sampling schedule is what the figure is really about. Change the schedule and you have changed the figure, which is why two devices with similar cells can state seven days and fourteen.
None of these listings describes the schedule behind their number. They print the output of a calculation and keep the inputs.
What shortens it
- Continuous rather than periodic sensor sampling, which several of these listings name as a feature in its own right.
- A screen, where the device has one, and any setting that keeps it lit longer.
- Frequent syncing to a phone, which wakes the radio on a schedule the app decides rather than the device.
- Cold weather, which reduces the usable capacity of every lithium cell temporarily.
- Age. Cells lose capacity across charge cycles, and no listing in this catalog states a figure for that.
What the listing does not say
- Which features were switched on while the figure was produced.
- Whether the number assumes a phone in range or out of it.
- What the figure looks like after a year of charge cycles.
And the fee side
This is the category where the runtime figure and the recurring cost are most likely to appear in different listings. Three tracker listings here state a membership or app fee and only one of those three states a runtime figure at all.