Capacitor Calculator
Calculate capacitive reactance, impedance, and analyze capacitor properties
Microfarads (µF)
Volts (V) - rated voltage of capacitor
Hertz (Hz) - leave empty if not calculating reactance
How to Use This Calculator
Enter Capacitance
Enter the capacitor value in microfarads (µF). This is the capacitance rating printed on the capacitor.
Enter Operating Voltage (Optional)
Enter the voltage rating of the capacitor in volts. This helps identify the capacitor but doesn't affect reactance calculation.
Enter Frequency (Optional)
Enter the operating frequency in hertz (Hz) to calculate capacitive reactance. Leave empty if you only want to record capacitor specifications.
View Results
Click calculate to see the capacitive reactance at the specified frequency. The reactance is shown in ohms or kilohms.
Formula
XC = 1 / (2π × f × C)
Where:
- XC = Capacitive reactance (Ω)
- f = Frequency (Hz)
- C = Capacitance (F)
- π ≈ 3.14159
Key Relationships:
- Reactance decreases as frequency increases
- Reactance decreases as capacitance increases
- At DC (f = 0), reactance is infinite (capacitor blocks DC)
- At high frequencies, reactance approaches zero (capacitor passes AC)
Example 1:
Capacitance = 100 µF, Frequency = 1000 Hz
C = 100 × 10-6 = 0.0001 F
XC = 1 / (2 × π × 1000 × 0.0001)
XC = 1 / 0.628 = 1.59 Ω
Example 2:
Capacitance = 10 µF, Frequency = 60 Hz
XC = 1 / (2 × π × 60 × 10 × 10-6)
XC = 1 / 0.00377 = 265.3 Ω
About Capacitor Calculator
The Capacitor Calculator is a free online tool that helps you calculate capacitive reactance and analyze capacitor behavior in AC circuits. Capacitive reactance is the opposition that a capacitor offers to alternating current, similar to resistance but frequency-dependent. This calculator is essential for filter design, impedance matching, and understanding how capacitors behave in AC circuits.
When to Use This Calculator
- Filter Design: Calculate reactance for high-pass, low-pass, and band-pass filters
- Impedance Matching: Determine capacitor values for impedance matching networks
- Power Factor Correction: Calculate capacitor values for power factor correction
- Coupling Circuits: Design AC coupling capacitors for signal transmission
- Educational Purposes: Learn about capacitive reactance and AC circuit behavior
Why Use Our Calculator?
- ✅ Accurate Calculations: Uses the correct capacitive reactance formula
- ✅ Easy to Use: Simple interface requiring capacitance and frequency
- ✅ Multiple Units: Displays results in ohms or kilohms automatically
- ✅ Educational: Includes formulas and examples for learning
- ✅ Free Tool: No registration or payment required
- ✅ Instant Results: Get calculations in seconds
Common Applications
Filter Circuits: Capacitors are used in filters to block or pass certain frequencies. A 100 µF capacitor at 60 Hz has a reactance of 26.5 Ω, allowing it to pass AC while blocking DC. This is essential in power supply filters and audio circuits.
AC Coupling: In amplifier circuits, capacitors are used to couple AC signals while blocking DC bias. The reactance must be low enough at the signal frequency to avoid significant voltage drop.
Power Factor Correction: Capacitors are added to inductive loads to improve power factor. The capacitor reactance must be calculated to provide the correct amount of reactive power compensation.
Impedance Matching: In RF circuits, capacitors are used for impedance matching. Calculating reactance helps design matching networks that transfer maximum power.
Tips for Accurate Results
- Enter capacitance in microfarads (µF) - the calculator converts to farads internally
- Reactance is inversely proportional to frequency - higher frequency means lower reactance
- Reactance is inversely proportional to capacitance - larger capacitor means lower reactance
- At DC (0 Hz), reactance is infinite - capacitors block DC current
- Consider capacitor tolerance - actual reactance may vary by ±5-20%
- For AC circuits, ensure capacitor voltage rating exceeds peak AC voltage
Frequently Asked Questions
What is capacitive reactance?
Capacitive reactance (Xc) is the opposition that a capacitor offers to alternating current. Unlike resistance, reactance depends on frequency - higher frequency means lower reactance. It's measured in ohms (Ω).
Why does reactance decrease with frequency?
At higher frequencies, the capacitor charges and discharges more quickly, allowing more current to flow. This means less opposition to current, resulting in lower reactance. The relationship is inverse: Xc = 1/(2πfC).
What happens at DC (0 Hz)?
At DC (direct current), frequency is 0, making reactance infinite. This means capacitors block DC current completely, which is why they're used for AC coupling and DC blocking in circuits.
Is reactance the same as resistance?
No, reactance and resistance are different. Resistance opposes both DC and AC equally, while reactance only opposes AC and depends on frequency. Reactance also causes a 90-degree phase shift between voltage and current.
Can I use this for capacitors in series or parallel?
This calculator finds reactance for a single capacitor. For multiple capacitors, calculate each reactance separately, then combine them: series reactances add (Xtotal = X1 + X2), parallel reactances combine like parallel resistors (1/Xtotal = 1/X1 + 1/X2).