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Tap the Capacity card on Today.
Two pills at the top switch between views. Details — today’s figure, and the three arms it is built from:
  • Autonomic — your overnight physiology, chiefly HRV and resting heart rate
  • Sleep — how well and how long you slept
  • Feelings — what you reported in the Daily Journal
A line beneath names the one holding you back — “yesterday’s feelings is today’s main limiter” — which is usually the most useful sentence on the screen. Trends — the same figure over time, with the underlying measurements beneath it. This is the more useful view, for the usual reason.

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What feeds it

Capacity is built from overnight physiology and recent load:
  • HRV — the largest single input
  • Resting heart rate — and its direction over recent days
  • Sleep — duration and quality
  • Recent training load — what you have asked of yourself lately
  • Respiratory rate and heart-rate dip, where available
Not all of these will be present for everyone. The calculation uses what it has and says so rather than substituting defaults.

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”Needs HRV”

The commonest message here. It means the overnight HRV reading has not arrived. Usual causes, in order of likelihood:
  1. Your wearable has not synced yet — often fixed by opening its own app
  2. You did not wear it, or it ran out of charge
  3. Your Capacity source is set to a device you do not wear at night
The third one is worth checking if it keeps happening: see Choosing your sources, and remember that the device you wear in bed should be your Capacity source, even if a different one is your main device.

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”Sleep data not ready”

A message you will meet on the Today screen rather than here, usually first thing in the morning.
It means the same thing as Needs sleep: last night has not arrived from your source yet. Capacity cannot be worked out without it, so the app says so instead of computing something from a night it cannot see. It names the source it is waiting on. Open that source’s own app to make it sync, then pull down on Today to refresh.
Waking before your wearable has synced is the ordinary cause, and it resolves itself within minutes. Worth reporting only if the message is still there hours later with the wearable’s own app showing the night.

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Blank baseline metrics

On the Trends view, some measurements — respiratory rate, heart-rate dip — stay blank for one to two weeks. They are compared against your baseline, and in your first fortnight you do not have one. This is not the app failing to fetch something.

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The calibration caveat

Capacity is one of the four engines we are still tuning. The number is real and grounded in published science, but the weights are still being tuned — partly against your data.If it produces something that feels clearly wrong for a day you can explain — a terrible night that scored well, a great night that scored badly — that is one of the most valuable things you can tell us.

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Ask Eir

The circular button gives a plain-language reading. See Ask Eir.