Capacitor Impedance Calculator Formula
Understand the math behind the capacitor impedance calculator. Each variable explained with a worked example.
Formulas Used
Capacitive Reactance (Xc)
reactance = 1 / (2 * pi * frequency_hz * cap_f)Variables
| Variable | Description | Default |
|---|---|---|
capacitance_uf | Capacitance(µF) | 10 |
frequency_hz | Frequency(Hz) | 1000 |
cap_f | Derived value= capacitance_uf / 1000000 | calculated |
How It Works
Capacitive Reactance
Xc = 1 / (2 x pi x f x C)
Reactance decreases with frequency: capacitors pass high frequencies and block low frequencies (DC).
Worked Example
10 uF capacitor at 1 kHz.
capacitance_uf = 10frequency_hz = 1000
- 01C = 10 uF = 0.00001 F
- 02Xc = 1 / (2 x pi x 1000 x 0.00001)
- 03Xc = 1 / 0.06283 = 15.92 ohms
Frequently Asked Questions
Why does reactance decrease with frequency?
At higher frequencies the capacitor charges/discharges faster, presenting less opposition to current flow.
Is reactance the same as resistance?
No. Reactance causes a 90-degree phase shift between voltage and current. It does not dissipate power.
What about ESR?
Real capacitors have equivalent series resistance (ESR) that adds to the impedance and does dissipate power.
Ready to run the numbers?
Open Capacitor Impedance Calculator