Solve Q = C × V for whichever value you're missing — charge, capacitance, or voltage.
How to Use the Capacitance Calculator
Pick which quantity to solve for — Charge, Capacitance, or Voltage — then fill in the other two fields. Charge and capacitance each carry their own unit dropdown, since real capacitor values rarely land on a clean whole coulomb or farad.
Capacitance is a capacitor's willingness to store charge at a given voltage — nothing more mystical than that. Double the voltage across the same capacitor and it holds twice the charge; the ratio between the two never changes for an ideal capacitor, which is exactly what makes capacitance a fixed, describable property of the component rather than a moving target. The relationship rearranges three ways depending on what's missing:
Q = C × V
C = Q ÷ V
V = Q ÷ CQ is charge in coulombs, C is capacitance in farads, V is voltage in volts. A farad is an enormous unit in practice — a 1F capacitor storing 1C at 1V would be the size of a soup can or bigger for anything but a supercapacitor — so nearly everything on a circuit board gets measured in microfarads, nanofarads, or picofarads instead, and charge correspondingly in microcoulombs or smaller.
Take a fairly ordinary 470 nF capacitor charged to 10V: that's 4.7 µC sitting on the plates, a number too small to mean anything as a fraction of a full coulomb. This calculator does that unit juggling for you — switch the dropdown and the same physical quantity just gets relabeled at whatever scale is legible.
Two failure modes are worth flagging before you plug numbers in. Solving for capacitance with a zero voltage entered has no answer — charge divided by zero volts is undefined, not infinite in any useful sense — and the same goes for solving voltage against a zero-capacitance component, since a capacitor with no capacitance can't be holding charge at all. Both cases throw an error message instead of a nonsense number.
Need this relationship for a single fixed direction rather than an any-two solver? The Capacitance to Charge Conversion Calculator elsewhere on this site does just the Q = C × V leg without the mode toggle, which is often the faster tool when you already know exactly which two values you're starting from.