Clock Repair Calculators
Free clock repair calculators for pendulum length, gear ratios, mainspring sizing, and escapement timing.
Tools for horologists and clock enthusiasts.
Pendulum length, beat rate, gear ratios and mainspring sizing. 9 calculators for horologists. The physics behind the swing sits under Physics.
Pendulum length runs on Huygens’ 1673 result, period equals 2π times the square root of length over gravity, and the square root is what makes regulation feel counterintuitive. Quadrupling the length only doubles the period, and a seconds-beating pendulum lands near 994 mm almost regardless of what the bob is made of. Two things fall out of that. Bob weight does not affect rate, which surprises nearly everyone. Gravity does, which is why a clock carried a long way north or up a mountain has to be regulated again.
Escapement beat rate counts ticks per hour, and the trap is that a beat is half a period. One full swing gives two beats, so beats per hour is 7,200 divided by the period, not 3,600. Halve that once and every gear ratio downstream comes out wrong.
Pivot wear and rate error pages assume the clock is in beat. Level it first.
Clock Pivot Bushing Wear Tolerance
Determine when a clock pivot hole needs re-bushing. Compares measured hole size to acceptable wear, with replacement bushing size selection.
Clock Wheel Tooth Count Calculator
Calculate the gear tooth count needed for any output RPM ratio in a clock train. Useful for replacement wheels, train design, and verifying restoration.
Quartz Watch Battery Life Calculator
Estimate quartz watch and clock battery life by movement type and battery capacity. Get years before replacement for analog, chronograph, and digital movements.
Weight-Driven Clock Drop Time Calculator
Calculate how long a weight-driven clock runs between windings. Enter cord drop length and gear train ratio to get the run time in hours and days.
Clock Rate Error Calculator (Seconds Per Day)
Calculate clock seconds-per-day error from observed gain or loss over a period. Includes pendulum-length adjustment to regulate the rate.
Clock Escapement Beat Rate Calculator
Calculate clock escapement beat rate in BPH from pendulum length, or the length needed for a target beat rate, with the adjustment to correct timing.
Clock Mainspring Size Calculator
Calculate clock mainspring width, thickness, and length for mechanical clock repair. Returns spring strength and replacement specifications for restoration.
Clock Gear Train Ratio Calculator
Calculate clock gear train ratios from wheel and pinion tooth counts. Returns total ratio needed for 60-minute and 12-hour hand cycles in mechanical movements.
Pendulum Clock Length Calculator
Calculate pendulum length from beat period using L = g × (T/2π)². Returns length in inches and cm for grandfather, mantel, and cuckoo clock adjustments.