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Capacitor tolerance calculator

Enter measured and rated microfarads. See how far off the capacitor is and whether it's within ±6%.

  • Free, no sign-up
  • Built for your phone
  • Same math as the FieldLoom app
Enter your readingsResults update as you type
Printed on the capacitor label.

How to check a capacitor

Off rated (%) = (measured µF − rated µF) ÷ rated µF × 100
  1. Turn off power at the disconnect and confirm it's off.
  2. Discharge the capacitor safely.
  3. Remove the wires and measure with your meter's capacitance setting.
  4. On a dual capacitor, test HERM to C and FAN to C separately.
Worked example

A 45 µF capacitor measures 41 µF. That's (41 − 45) ÷ 45 × 100 = −8.9%, outside ±6% (42.3–47.7 µF). Replace it.

Replace with the same µF rating and the same or higher voltage rating.

Questions

What is the tolerance on a run capacitor?

Most HVAC run capacitors are rated ±5% or ±6%. The tolerance is printed on the label. FieldLoom uses ±6% by default.

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