THE NUMORIX GUIDE
How to use the Capacitance Calculator
Last reviewed September 14, 2026
What this calculator does
Capacitance is calculated from C = Q / V.
Formula and method
Capacitance is calculated from C = Q / V. The engine then estimates ideal stored energy with E = 1/2 C V^2 using the entered charge Q and voltage V.
Variables and inputs
Voltage V is in volts and charge Q is in coulombs; the UI defaults to 12 V and 0.001 C and requires a positive voltage. Capacitance is returned in farads and stored energy in joules, with both engine values rounded to six decimal places.
Worked example
For V = 12 V and Q = 0.001 C: C = 0.001 / 12 = 8.3333e-5 F, displayed as 0.000083 F, and E = 1/2(8.3333e-5)(12^2) = 0.006 J.
How to interpret the result
Capacitance measures how much charge a capacitor stores per volt. The energy result is the ideal energy associated with that charge-voltage state, not the usable energy after leakage, resistance, or a converter's losses.
Common mistakes to avoid
Convert microcoulombs and microfarads before substituting, and do not confuse charge Q with current I. Keep voltage in volts; a negative charge is a signed input, while the physical energy of a capacitor is normally based on a nonnegative stored state.
Assumptions and limitations
The model treats the capacitor as linear and ideal. It does not include dielectric geometry, voltage rating, leakage, equivalent series resistance, discharge behavior, or AC frequency; the UI only guards the voltage and does not reject a negative charge.
Practical use and checks
The Capacitance Calculator uses C = Q/V and estimates ideal stored energy with E = one-half C V squared. Enter voltage 12 V and charge 0.001 C as a check; capacitance should be about 0.0000833 F and stored energy about 0.006 J. Convert the capacitance to 83.3 microfarads if that is the practical component scale. If voltage doubles while charge is held fixed, the calculated capacitance halves because the inputs describe a different charge-voltage state. Use the result to connect measured charge and voltage or to estimate the ideal energy in a capacitor at a specified voltage. Keep coulombs and volts consistent, and do not substitute current for charge. Physical energy is nonnegative for an ordinary capacitor even though a signed charge can represent polarity. The model assumes a linear, ideal capacitor; it omits dielectric geometry, voltage rating, leakage, equivalent series resistance, tolerance, frequency, discharge path, and converter losses. A negative or zero voltage is an edge case for the quotient and should be handled through the circuit's sign convention, not treated as a normal component specification. For a design decision, compare the ideal result with the capacitor's rated voltage, ripple current, temperature, and stored-energy hazard.