๐ Capacitor Charge & Energy Calculator
Enter a capacitorโs capacitance and voltage to calculate the electric charge it stores (Q=CV) and the energy stored in its electric field (E=ยฝCVยฒ).
How to use
- Enter the capacitance value and select its unit (pF, nF, ยตF, mF, F).
- Enter the voltage (V).
- The charge and energy are calculated automatically.
How the calculation works
This tool calculates how much charge and energy a capacitor stores at a given voltage. Charge Q = C ร V (coulombs) Energy E = ยฝ ร C ร Vยฒ (joules) C is capacitance in farads and V is voltage in volts. Charge rises in proportion to voltage, but energy rises with the square of voltage, so doubling the voltage stores four times the energy. Capacitance can be entered from pF (pico) up to F (farads). Results are shown with a p, n, ยต or m prefix chosen to suit their size.
Worked example
A 100 ยตF capacitor at 12 V Charge: 100 ร 10โปโถ ร 12 = 1.2 mC Energy: ยฝ ร 100 ร 10โปโถ ร 12ยฒ = 7.2 mJ A 1 F supercapacitor at 5 V Charge: 5 C Energy: 12.5 J
Things to be aware of
- Every capacitor has a voltage rating. Never exceed it, and mind the polarity (+ and โ) of electrolytic capacitors.
- Large capacitors hold their charge after the power is off and can give a shock or damage parts. Discharge them through a resistor before touching them.
- The usable energy is only what is released down to the lowest voltage the device can run on: ยฝC(V1ยฒ โ V2ยฒ) as the voltage falls from V1 to V2.
FAQ
What formulas does this use?
It uses the fundamental capacitor formulas: charge Q = C ร V, and stored energy E = ยฝ ร C ร Vยฒ.
How is the unit of the result chosen?
Results are based on coulombs (C) for charge and joules (J) for energy, with the p (pico), n (nano), ยต (micro), or m (milli) prefix chosen automatically based on the magnitude of the value.
Which capacitance unit should I choose?
Common electrolytic capacitors are usually rated in ยตF (microfarads), while ceramic capacitors are often in the pF to nF range. Match the unit to whatโs printed on your component.