Capacitance Units
Capacitance is measured in farads (F), the SI unit of capacitance. One farad represents the ability of a capacitor to store one coulomb of electrical charge when one volt is applied across its terminals. Because one farad is an extremely large value for most electronic circuits, smaller units such as millifarads, microfarads, nanofarads and picofarads are used much more frequently.
The Farad (F)
The farad (F) is named after the English scientist Michael Faraday.
One farad is defined as:
1 F = 1 Coulomb / Volt
A one-farad capacitor stores one coulomb of charge when charged to one volt.
Common Capacitance Units
| Unit | Symbol | Equivalent Value |
|---|---|---|
| Farad | F | 1 F |
| Millifarad | mF | 0.001 F |
| Microfarad | µF | 0.000001 F |
| Nanofarad | nF | 0.000000001 F |
| Picofarad | pF | 0.000000000001 F |
Unit Conversion Table
| Equivalent Values |
|---|
| 1 F = 1,000 mF |
| 1 mF = 1,000 µF |
| 1 µF = 1,000 nF |
| 1 nF = 1,000 pF |
| 1 F = 1,000,000 µF |
| 1 F = 1,000,000,000 nF |
| 1 F = 1,000,000,000,000 pF |
Quick Conversion Examples
| Value | Equivalent |
|---|---|
| 0.1 µF | 100 nF |
| 0.01 µF | 10 nF |
| 0.001 µF | 1 nF |
| 1000 pF | 1 nF |
| 2200 pF | 2.2 nF |
| 4700 pF | 4.7 nF |
| 100 nF | 0.1 µF |
| 470 nF | 0.47 µF |
| 2200 µF | 2.2 mF |
Typical Capacitance Ranges
| Capacitance | Typical Application |
|---|---|
| 1–100 pF | RF tuning circuits. |
| 100 pF–10 nF | Oscillators and filters. |
| 10 nF–100 nF | Signal coupling and decoupling. |
| 100 nF | Microcontroller bypass capacitor. |
| 1–100 µF | Audio coupling and timing circuits. |
| 100–10,000 µF | Power supply filtering. |
| 1–5,000 F | Supercapacitors and energy storage. |
Reading Capacitor Values
Manufacturers may mark capacitors using their actual value or a numerical code.
| Marking | Capacitance |
|---|---|
| 100 pF | 100 pF |
| 1 nF | 1000 pF |
| 10 nF | 0.01 µF |
| 100 nF | 0.1 µF |
| 1 µF | 1000 nF |
| 104 | 100 nF (0.1 µF) |
| 473 | 47 nF |
| 223 | 22 nF |
| 472 | 4.7 nF |
| 102 | 1 nF |
Memory Aid
Each step between units changes by a factor of one thousand.
F ↓ mF ↓ µF ↓ nF ↓ pF
Moving down the list multiplies by 1,000. Moving up the list divides by 1,000.
Common Mistakes
| Mistake | Correct Information |
|---|---|
| Confusing mF with µF. | 1 mF = 1,000 µF. |
| Using 100 pF instead of 100 nF. | 100 nF is 1,000 times larger. |
| Ignoring capacitor codes. | Many small capacitors use three-digit markings. |
| Mixing nF and µF. | 1 µF = 1,000 nF. |
Real-World Examples
| Equipment | Typical Capacitor |
|---|---|
| Arduino | 100 nF ceramic capacitor. |
| ESP32 Module | 10 µF electrolytic capacitor. |
| Audio Amplifier | 4700 µF filter capacitor. |
| FM Radio | 22 pF tuning capacitor. |
| Power Supply | 2200 µF smoothing capacitor. |
Key Points
- The SI unit of capacitance is the farad (F).
- Most electronic circuits use µF, nF and pF.
- Each step between units is a factor of 1,000.
- Understanding unit conversions helps prevent component selection errors.
- Many capacitors are identified using standard three-digit value codes.