What is the Capacitor Calculator?
This is the capacitor calculator — an all-encompassing tool that helps you answer the questions What is the capacitor code? and What is the general formula for capacitors? While this calculator is both a code-to-capacity and capacity-to-code converter, it also finds the stored charge for a capacitor with specific parameters. Have you ever wondered what the 3-digit capacitor codes mean? Below you'll find an explanation — with examples!
Capacitor Formula
The most general equation for capacitors states that:
C = Q / V
where:
- C — Capacitance of the electronic element (farads, F);
- Q — Electrical charge stored in the capacitor (coulombs, C); and
- V — Voltage on the capacitor (volts, V).
The formula indicates that the capacitor is a passive element capable of storing electric charge as long as we apply some voltage across it. Rearranged, the charge stored is Q = C × V.
There are multiple types of capacitors. The most popular are parallel plates and cylindrical ones, but spherical capacitors are also used. The general capacitor formula is the same in each case — charges of equal absolute value but opposite sign are stored on opposing sides of the capacitor. Capacitors can be arranged both in series and in parallel; in either case the system behaves like a single capacitor whose resulting capacitance combines all parts.
Capacitor Code
Every capacitor usually has two numbers that characterize it: its capacitance and its voltage rating. The voltage rating tells us the maximum voltage at which the element will still work correctly. Producers often write the capacity directly, so a capacitor marked 220 µF 25 V simply has a capacity of 220 µF and works safely up to 25 V.
However, when the capacitance is lower than 100 µF, we usually find a 3-digit capacitor code that defines the value. The rule is simple: the first and second digits give the capacity in pF (picofarads), while the third digit is a multiplier factor (the power of 10) — for the number n, the capacitance is multiplied by 10ⁿ. The last digit is usually within the range 0–6. If there is a one- or two-digit number, it simply defines the value directly in pF.
Example: code 104
- The first two digits give the capacity in pF: 10.
- The 3rd digit is the multiplier factor: 10⁴ = 10,000.
- The resulting value is 10 pF × 10⁴ = 10⁵ pF = 100 nF = 0.1 µF.
Reverse example: C = 1.24 µF
- We need two significant figures, so round the value: 1.24 µF → 1.2 µF, giving the first two digits 12.
- Using picofarads: 1.2 µF = 1,200,000 pF = 12 × 10⁵ pF, so the 3rd digit is 5.
- Therefore, the capacitor code for 1.24 µF is 125.
Fortunately, this capacitor calculator works both as a code-to-capacity and a capacity-to-code converter! Just choose the appropriate mode, and the result appears in the blink of an eye.
What is the Capacitor Tolerance Code?
Right next to the 3-digit capacitor code, you can usually find a letter describing the tolerance range within which the actual capacitance lies. Tolerances can be written as absolute values (in pF) or as percentage ranges. The most commonly used tolerance codes are:
| Letter | Tolerance |
|---|---|
| B | ±0.1 pF |
| C | ±0.25 pF |
| D | ±0.5 pF |
| F | ±1% |
| G | ±2% |
| J | ±5% |
| K | ±10% |
| M | ±20% |
| Z | +80% / −20% |
For example, a capacitor marked 104J has a nominal value of 100 nF (0.1 µF) with a ±5% tolerance, meaning the real capacitance lies between roughly 95 nF and 105 nF.
Units and Measurement Systems
This calculator supports both the Metric (SI) and American unit systems for arranging the conversion output. Capacitance is expressed across the full prefix range:
- F (farad), mF (millifarad), µF (microfarad), nF (nanofarad), pF (picofarad)
- Charge: C (coulomb), mC, µC, nC, pC
- Voltage: kV (kilovolt), V (volt), mV (millivolt)
FAQs
What does the capacitor code 104 mean?
It means 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. The first two digits (10) are the significant figures and the third digit (4) is the power-of-ten multiplier.
How do I read a small ceramic capacitor?
If you see a three-digit number, apply the code rule above. If you see a one- or two-digit number, that value is simply the capacitance in picofarads. A trailing letter indicates the tolerance.
What is the general capacitor formula?
C = Q / V. The capacitance equals the stored charge divided by the voltage across the plates. Equivalently, the stored charge is Q = C × V, and the stored energy is E = ½ × C × V².
Why is the multiplier digit usually 0–6?
Because practical ceramic and film capacitors range from a few picofarads up to about 1 µF, the power-of-ten multiplier rarely needs to exceed 10⁶. Larger electrolytic capacitors are normally labeled directly in µF instead of using a code.