When to use this calculator
Capacitive reactance falls as frequency rises, so the same capacitor presents different opposition to different AC frequencies.
Explore the ac power & reactance calculators for other questions in this topic. For a related calculation, use the Decibel Power Ratio Calculator: Express a power ratio as a decibel difference.
PUTTING IT INTO PRACTICE
Capacitive Reactance: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Frequency (Hz) | 50 |
| Capacitance (μF) | 100 |
| Result | 31.830989 Ω |
- Check the input labels and enter the example values above.
- Apply the relationship: Reactance = 1/(2π × frequency × capacitance in farads).
- The result is 31.830989 Ω, rounded for display.
How to interpret your result
Magnitude only; ideal capacitive impedance has a negative imaginary sign.
Use RMS values in the AC power relationships. Apparent power is measured in VA and real power in watts. Pure-sine conversions and balanced three-phase equations only apply under their stated assumptions.
Frequently asked questions
Why can volt-amps differ from watts?
Apparent power is the RMS voltage-current product, while real power also reflects power factor. They are numerically equal only at a power factor of one.
When is the capacitive reactance calculator useful?
Capacitive reactance falls as frequency rises, so the same capacitor presents different opposition to different AC frequencies.
How do I use the capacitive reactance calculator?
Enter frequency (hz), capacitance (μf). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Reactance = 1/(2π × frequency × capacitance in farads).
What should I check before using the result?
Magnitude only; ideal capacitive impedance has a negative imaginary sign.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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