Farads to Amps Converter
A 100 microfarad capacitor on a 230 volt, 50 hertz supply passes about 7.23 amps.
Quick answer: Multiply the voltage by 2 times pi, the frequency and the capacitance in farads. For example, 100 uF, 230 V, 50 Hz is 7.226 A, 10 uF, 120 V, 60 Hz is 0.4524 A and 1 uF, 12 V, 1,000 Hz is 0.0754 A.
The farads to amps formula
Current in amps equals voltage times 2 times pi times frequency times capacitance.
It is the RMS current through an ideal capacitor on an AC supply.
Take 100 uF, 230 V, 50 Hz. 230 × 2 × π × 50 × 0.0001 gives 7.226 A.
Take 10 uF, 120 V, 60 Hz. 120 × 2 × π × 60 × 0.00001 gives 0.4524 A.
Current from reactance
A capacitor on AC passes a current equal to the voltage divided by its reactance. The reactance is 1 divided by 2 times pi times frequency times capacitance (TutorChase: Capacitive reactance).
Putting the two together gives the voltage times 2 times pi times frequency times capacitance.
How to convert farads to amps step by step
- Read the capacitance in farads, the AC voltage and the frequency.
- Multiply 2 times pi by the frequency and by the capacitance.
- Multiply the result by the voltage.
- Read the answer in amps, or multiply by 1,000 for milliamps.
Example 1: 100 uF, 230 V, 50 Hz
- Start with 100 uF, 230 V, 50 Hz.
- 230 × 2 × π × 50 × 0.0001 = 7.226.
- The current is 7.226 A.
100 uF, 230 V, 50 Hz = 7.226 A
Example 2: 10 uF, 120 V, 60 Hz
- Start with 10 uF, 120 V, 60 Hz.
- 120 × 2 × π × 60 × 0.00001 = 0.4524.
- The current is 0.4524 A.
10 uF, 120 V, 60 Hz = 0.4524 A
Example 3: 1 uF, 12 V, 1,000 Hz
- Start with 1 uF, 12 V, 1,000 Hz.
- 12 × 2 × π × 1,000 × 0.000001 = 0.0754.
- The current is 0.0754 A.
1 uF, 12 V, 1,000 Hz = 0.0754 A
The three examples below use common sizes.
Each one shows the sum in full.
farads to amps conversion table
| Capacitor, voltage and frequency | Current (A) | Current (mA) |
|---|---|---|
| 1 uF, 12 V, 1,000 Hz | 0.0754 A | 75.398 mA |
| 1 uF, 230 V, 50 Hz | 0.0723 A | 72.257 mA |
| 10 uF, 12 V, 1,000 Hz | 0.754 A | 753.98 mA |
| 10 uF, 120 V, 60 Hz | 0.4524 A | 452.39 mA |
| 10 uF, 230 V, 50 Hz | 0.7226 A | 722.57 mA |
| 20 uF, 230 V, 50 Hz | 1.445 A | 1,445.13 mA |
| 50 uF, 230 V, 50 Hz | 3.613 A | 3,612.83 mA |
| 100 uF, 12 V, 50 Hz | 0.377 A | 376.99 mA |
| 100 uF, 120 V, 60 Hz | 4.524 A | 4,523.89 mA |
| 100 uF, 230 V, 50 Hz | 7.226 A | 7,225.66 mA |
| 100 uF, 230 V, 60 Hz | 8.671 A | 8,670.8 mA |
| 200 uF, 120 V, 60 Hz | 9.048 A | 9,047.79 mA |
The highlighted row is the default of the calculator. The last column gives mA.
A quick mental shortcut for farads to amps
Multiply the farads, the volts and the hertz, then by 6.28. For 100 uF at 230 V and 50 Hz that is 0.0001 x 230 x 50 x 6.28, which is about 7.2 A.
Double the capacitance and the current doubles.
A small capacitor on mains
A 1 uF capacitor on 230 V at 50 Hz passes about 72 mA. That is enough to cause a serious shock.
Never judge a part as safe because it is small.
Rated voltage and current
Capacitors have a maximum voltage and a maximum ripple current on their data sheet. The result here is only the ideal current, so check it against the part ratings.
A capacitor run beyond its ratings can overheat or fail.
RMS and ideal parts
Use the RMS voltage, such as 230 V, and the answer is the RMS current. A real capacitor also has a little resistance and inductance that this page ignores.
For most checks the ideal result is a good guide.
Quick conversion answers
| Conversion | Result |
|---|---|
| 100 uF, 230 V, 50 Hz | 7.226 A |
| 10 uF, 120 V, 60 Hz | 0.4524 A |
| 1 uF, 12 V, 1,000 Hz | 0.0754 A |
| 200 uF, 120 V, 60 Hz | 9.048 A |
Where this conversion is used
Designers check the current a capacitor draws from a supply.
Students link capacitance, voltage and current in AC circuits.
Common mistakes to avoid
- Entering microfarads as farads. The answer would be one million times too large.
- Using peak voltage. Use the RMS value to get RMS current.
- Using DC. A capacitor passes no steady current at DC.
- Ignoring the safety limits. Mains voltage across a capacitor can be dangerous.
Related converters
More capacitor, voltage and frequency sets
0.1 uF, 230 V, 50 Hz is 0.007226 A. 2.2 uF, 120 V, 60 Hz is 0.09953 A. 4.7 uF, 230 V, 50 Hz is 0.3396 A.
10 uF, 5 V, 10,000 Hz is 3.142 A. 22 uF, 24 V, 50 Hz is 0.1659 A. 33 uF, 230 V, 50 Hz is 2.384 A.
47 uF, 12 V, 400 Hz is 1.417 A. 68 uF, 120 V, 60 Hz is 3.076 A. 470 uF, 12 V, 50 Hz is 1.772 A.
Doubling the first number
0.2 uF, 230 V, 50 Hz is 0.01445 A. 4.4 uF, 120 V, 60 Hz is 0.1991 A. 9.4 uF, 230 V, 50 Hz is 0.6792 A.
20 uF, 5 V, 10,000 Hz is 6.283 A. 44 uF, 24 V, 50 Hz is 0.3318 A. 66 uF, 230 V, 50 Hz is 4.769 A.
94 uF, 12 V, 400 Hz is 2.835 A. 136 uF, 120 V, 60 Hz is 6.152 A. 940 uF, 12 V, 50 Hz is 3.544 A.
The same capacitor at different voltages
100 uF, 12 V, 50 Hz is 0.377 A. 100 uF, 120 V, 50 Hz is 3.77 A. 100 uF, 230 V, 50 Hz is 7.226 A.
100 uF, 400 V, 50 Hz is 12.57 A.
Frequently asked questions
How do I convert farads to amps?
Multiply the voltage by 2 times pi, the frequency and the capacitance in farads.
How many amps does 100 uF pass at 230 V and 50 Hz?
About 7.226 A.
Does a capacitor draw current at DC?
Not once it is charged. The formula applies to AC.
Why does the current rise with frequency?
The reactance falls as the frequency rises, so more current flows.
Is the answer RMS?
Yes, if you use the RMS voltage.
Is it safe to connect a capacitor across mains?
Only if it is rated for it and installed by a qualified person.
Sources
- TutorChase: Capacitive reactance (tutorchase.com)
- Wikipedia: Electrical reactance (en.wikipedia.org)
