Use this horology calculation to interpret a stated watch, clock, timing-machine, water-resistance, alarm, or historical respiratory-timing quantity under its defined convention.

Starting Reserve Hours (h)

Required number input.

Elapsed Hours (h)

Required number input.

Remaining power-reserve hours after elapsed running hours, with no winding during the interval. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Remaining Hours (h)

The resulting remaining hours returned as a number.

• Mechanical-watch amplitude and beat measurements depend on lift angle, position, state of wind, movement condition, instrument setup, and elapsed sampling. ATM markings are test-pressure classifications rather than literal safe diving depths.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Confirm movement specifications and measure in multiple positions and power states; follow the manufacturer's water-resistance guidance and obtain pressure testing after case service.

• Amplitude Decline Power Reserve

  Observed linear balance-amplitude decline in degrees per hour over a running interval.

• Mainspring Turns Power Reserve

  Ideal running hours from usable barrel turns and measured running hours per barrel turn.

• Hand Wind Turns Per Day

  Average crown turns per day needed to replace a full wind distributed over its power reserve.