Purpose and context
What does the Workout Rest Timer do?
Browser timers can be delayed when a tab is throttled. This timer recalculates remaining time from elapsed timestamps instead of subtracting one each interval.
Who it supports: General workout timing.
Transparent calculation
Formula and calculation method
The display updates frequently, but the authoritative remaining value comes from the high-resolution end timestamp.
Worked calculation example
A 90-second rest started at timestamp T ends at T + 90,000 ms even if a screen update is briefly delayed.
The live calculator retains greater internal precision and rounds only when presenting the result.
How to use the Workout Rest Timer
- Choose a rest preset.
- Start the timer after the set.
- Pause or add 15 seconds when needed.
- Reset before changing the planned interval.
Understanding your result
The result card identifies the value, unit, method, supporting values and an accuracy notice. Estimated and predicted outputs are labelled so that apparent precision is not mistaken for certainty.
Continue with the Interval Timer for a related measurement using its own documented method.
Accuracy, assumptions and limitations
Browser suspension can delay audible alerts, and the timer is not a medical or safety device.
Common input and interpretation mistakes
- Relying on setInterval tick count as elapsed time.
- Leaving sound on in a quiet environment.
- Using a countdown instead of monitoring symptoms or readiness.
Primary method source: https://www.w3.org/TR/hr-time-3/.
Frequently asked questions about Workout Rest Timer
It calculates from actual elapsed time, so delayed screen updates do not accumulate countdown drift.
Yes. The timer preserves the remaining duration and creates a new end timestamp on resume.
Presets include 30, 60 and 90 seconds plus 2, 3 and 5 minutes.
Device and browser power management can delay audio even when elapsed time is corrected.
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