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Capacitance Calculator

Calculate capacitance, charge, or voltage using Q = CV.

Capacitance Calculator tool

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About This Tool

Capacitance describes how much electric charge an ideal capacitor stores per volt of potential difference. This calculator solves the fundamental relationship Q = C × V for any one of its three quantities: capacitance C, charge Q, or voltage V. It also converts a capacitance value directly between farads, millifarads, microfarads, nanofarads, and picofarads. All calculations run locally in your browser.

How To Use It

  1. Choose whether to calculate capacitance, charge, or voltage.
  2. Enter the two known quantities and select their units.
  3. Read the result in the selected unit; the calculator converts values through SI units internally.
  4. For a direct unit conversion, use the capacitance unit converter below the formula result and choose the source and destination units.
  5. Use the result as an ideal capacitor calculation and check real component ratings, tolerance, dielectric behavior, and safety separately.

Examples

Find capacitance

If a capacitor stores 50 µC at 5 V, C = Q/V = 50 µC ÷ 5 V = 10 µF.

Find stored charge

A 4.7 µF capacitor at 5 V has ideal charge Q = CV = 23.5 µC.

Find voltage

If 50 µC is stored on a 10 µF capacitor, V = Q/C = 5 V.

Convert microfarads to nanofarads

One microfarad equals 1,000 nanofarads, so 4.7 µF converts to 4,700 nF.

Useful Notes

Capacitance formula

The defining ideal relationship is Q = C × V. Rearranging gives C = Q/V and V = Q/C. In SI units, one farad equals one coulomb per volt.

Common capacitance units

The farad is large for many practical components, so capacitors are commonly labeled in millifarads (mF), microfarads (µF), nanofarads (nF), or picofarads (pF). The calculator converts these prefixes before solving the equation.

Charge and voltage signs

The algebraic relationship can use signed charge and voltage. Their signs depend on which capacitor plate and voltage reference are being described. Capacitance itself is non-negative in this passive ideal-capacitor model, so charge and voltage must have matching signs when they are used to calculate C = Q/V.

Ideal capacitor assumption

Q = CV treats capacitance as a fixed value. Real capacitors have tolerance, leakage, equivalent series resistance, voltage coefficients, temperature effects, dielectric absorption, and maximum voltage ratings that this basic calculator does not model.

Division by zero

Calculating capacitance requires non-zero voltage, and calculating voltage requires non-zero capacitance. The calculator reports these undefined cases rather than returning an infinite result.

FAQ

What does one farad mean?

One farad is the capacitance that stores one coulomb of charge for one volt of potential difference: 1 F = 1 C/V.

Is µF the same as uF?

Yes in ordinary electronics notation. µF is the SI-symbol form for microfarad, while uF is commonly typed when the micro symbol is inconvenient.

Does this calculate capacitor energy?

No. This tool focuses on Q = CV. Capacitor energy uses a different relationship, such as E = 1/2 CV².

How many nanofarads are in one microfarad?

One microfarad (µF) equals 1,000 nanofarads (nF). Use the direct unit converter for other F, mF, µF, nF, and pF values.

Can this select a safe capacitor for a real circuit?

No. A numerical capacitance result does not determine safe voltage rating, dielectric type, tolerance, ripple-current capability, temperature range, polarity, or other component requirements.