With this capacitive reactance calculator you can calculate Xc, from the frequency and capacitance.
To improve understanding, we show the formula used, the definition and some examples.
More information about calculating the capacitive reactance:
- Formula to calculate the capacitive reactance.
- Capacitive reactance definition
- Typical capacitance units
- How to calculate the capacitive reactance
- Examples of capacitive ballast conversions
- How to use the capacitive reactance calculator
The formula that is used for the calculation of the capacitive reactance is the following:
Where:
- Xc = Capacitive reactance in ohms, (Ω)
- π (pi) = 3.142 (decimal) or as 22 ÷ 7 (fraction)
- ƒ = Frequency in hertz, (Hz)
- C = Faradays capacitance (F)
Return to the table of initial contents ↑
Definition of capacitive reactance:
The capacitive reactance is the complex impedance of a capacitor whose value changes with respect to the applied frequency.
When a DC (Direct Current) voltage is applied to a capacitor, the capacitor itself draws a charge current from the source and charges to a value equal to the applied voltage.
In the same way, when the supply voltage is reduced, the charge stored in the condenser is also reduced and the capacitor is discharged.
But in an AC (Alternating Current) circuit in which the applied voltage signal continuously changes from a positive polarity to a negative polarity at a rate determined by the frequency of the supply, as in the case of a sine wave voltage, For example, the capacitor is charged and discharged continuously at a rate determined by the frequency of supply.
As the capacitor is charged or discharged, a current flows through it, which is restricted by the internal impedance of the capacitor. This internal impedance is commonly known as capacitive reactance and is given the symbol Xc in ohms.
Unlike the resistance that has a fixed value, for example, 100Ω, 1kW, 10k etc, (this is because the resistance obeys Ohm’s Law), the capacitive reactance on the contrary varies with the applied frequency so that any variation in the power frequency will have a large effect on the value of the “capacitive reactance” in the capacitor.
As the frequency applied to the capacitor increases, its effect is to decrease its reactance (measured in ohms). In the same way, as the frequency through the capacitor decreases, its reactance value increases. This variation is called complex impedance of the capacitor.
Return to the table of initial contents ↑
Standard capacitance units:
| Prefix Name | Abbreviation | Weight | Equivalent Farad |
| Picofaradio | pF | 10 -12 | 0.000000000001 F |
| Nano farad | nF | 10 -9 | 0.000000001 F |
| Microfarad | μF | 10 -6 | 0.000001 F |
| Mili faradio | mF | 10 -3 | 0.001 F |
| Kilo faradio | kF | 10 3 | 1000 F |
| These are the commonly available capacitor values. The tolerances depend to a large extent on the type of dielectric and package. | ||||||||||
| PF | PF | PF | PF | μF | μF | μF | μF | μF | μF | μF |
| 1.0 | 10 | 100 | 1000 | 0.01 | 0.1 | 1.0 | 10 | 100 | 1000 | 10,000 |
| 1.1 | eleven | 110 | 1100 | |||||||
| 1.2 | 12 | 120 | 1200 | |||||||
| 1.3 | 13 | 130 | 1300 | |||||||
| 1.5 | fifteen | 150 | 1500 | 0.015 | 0.15 | 1.5 | fifteen | 150 | 1500 | |
| 1.6 | sixteen | 160 | 1600 | |||||||
| 1.8 | 18 | 180 | 1800 | |||||||
| 2.0 | twenty | 200 | 2000 | |||||||
| 2.2 | 22 | 220 | 2200 | 0.022 | 0.22 | 2.2 | 22 | 220 | 2200 | |
| 2.4 | 24 | 240 | 2400 | |||||||
| 2.7 | 27 | 270 | 2700 | |||||||
| 3.0 | 30 | 300 | 3000 | |||||||
| 3.3 | 33 | 330 | 3300 | 0.033 | 0.33 | 3.3 | 33 | 330 | 3300 | |
| 3.6 | 36 | 360 | 3600 | |||||||
| 3.9 | 39 | 390 | 3900 | |||||||
| 4.3 | 43 | 430 | 4300 | |||||||
| 4.7 | 47 | 470 | 4700 | 0.047 | 0.47 | 4.7 | 47 | 470 | 4700 | |
| 5.1 | 51 | 510 | 5100 | |||||||
| 5.6 | 56 | 560 | 5600 | |||||||
| 6.2 | 62 | 620 | 6200 | |||||||
| 6.8 | 68 | 680 | 6800 | 0.068 | 0.68 | 6.8 | 68 | 680 | 6800 | |
| 7.5 | 75 | 750 | 7500 | |||||||
| 8.2 | 82 | 820 | 8200 | |||||||
| 9.1 | 91 | 910 | 9100 | |||||||
Return to the table of initial contents ↑
How to calculate the capacitive reactance:
Step 1:
To calculate the capacitive reactance you must initially multiply 2xπxfxC and then divide the result by 1.
Example: a capacitor of 320nF, has a frequency of 1kHz, which will be the capacitive reactance, to find it you must multiply 2x320xπx10 ^ -9 × 1000 = 0.002010624 and the result is divided as follows: 1 / 0.00064 = 497.36 Ohm.
Return to the table of initial contents ↑
Examples of capacitive reactance conversions:
Example of capacitive reactance No1:
Calculate the capacitive reactance value of a 520nF capacitor at a frequency of 4 kHz.
Rta: // To know the answer you must multiply 2x520xπx10 ^ -9 × 4000 = 0.013069056 and then simply perform the following division: 1 / 0.013069056 = 76.5 Ohm.
Example of capacitive reactance No2:
Calculate the capacitive reactance value of a 520nF capacitor at a frequency of 10 kHz.
Rta: // To know the answer you must multiply 2x520xπx10 ^ -9 × 10000 = 0.03267264 and then simply perform the following division: 1 / 0.03267264 = 30.6 Ohm.
Example of capacitive reactance No3:
Calculate the capacitive reactance value of a 520nF capacitor at a frequency of 25kHz.
Rta: // The calculation, like the previous ones, is 2x520xπx10 ^ -9 × 25000 = 0.0816816 and then you must make the following division: 1 / 0.0816816 = 12.24 Ohm.
Therefore, it can be seen that as the frequency applied through the 520nF capacitor increases, from 4 kHz to 10 kHz to 25 kHz, its reactance value, Xc decreases, from about 76Ω to only 12Ω and this is always true as capacitive reactance.
Xc is always inversely proportional to the frequency with the current passing through the capacitor for a given voltage that is proportional to the frequency.
Return to the table of initial contents ↑
How to use the capacitive reactance calculator:
First you must insert the frequency, then the capacitance that can be in Nano faradio, micro farad, pico faradio or the unit in which this, finally you just have to click on calculate.