Crystal Load Capacitance Calculator

Enter C1, C2 and stray capacitance to get the load capacitance.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

A quartz crystal is only accurate at its rated frequency when the oscillator circuit presents it with the exact load capacitance (CL) printed on its datasheet. In the common Pierce oscillator topology, two capacitors C1 and C2 connect the crystal pins to ground, and the load they present is CL = (C1·C2)/(C1+C2) + Cstray, where Cstray accounts for PCB trace and pin capacitance, typically 2-5 pF.

Embedded and hardware engineers work this formula backward — starting from the crystal's specified load capacitance — to pick C1 and C2 values that keep the oscillator's actual frequency within its tolerance, since a mismatched load capacitance causes frequency pulling or unreliable startup.

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