Capacitance Converter

Storing Electrical Charge: Capacitance

Capacitance is one of the three fundamental properties of electrical circuits, alongside resistance and inductance. It represents the ability of a physical system to store an electrical charge. The components that perform this task are called Capacitors. Unlike chemical batteries, which store energy slowly and release it over hours, capacitors store electrical energy directly in an electrostatic field and can discharge all of their energy in a fraction of a millisecond.

This rapid discharge capability makes capacitors essential for almost every modern electronic device. They smooth out power supplies, filter out unwanted audio frequencies in stereo systems, and provide the massive instantaneous burst of energy required to trigger a camera flash. Because capacitor values span an enormous mathematical range, from trillionths of a unit up to whole units, mastering capacitance conversion is a mandatory skill for electronics engineering.

The Farad (F): An Astonishingly Large Unit

The International System of Units (SI) base unit for capacitance is the Farad (F), named after the brilliant English physicist Michael Faraday. One Farad is defined as the capacitance of a capacitor across which, when charged with one Coulomb of electricity, there is a potential difference of one Volt.

However, the Farad is a wildly impractical unit for daily use because it is astronomically huge. To put it in perspective: the natural self-capacitance of the entire planet Earth is only about 0.00071 Farads. For over a century, building a physical 1-Farad capacitor required a component the size of a barrel. Because of this, virtually all consumer electronics use highly fractional units.

Microfarads (μF), Nanofarads (nF), and Picofarads (pF)

When you open up a television or a computer motherboard, you will see cylindrical and disc-shaped capacitors covered in microscopic text. The values written on them are almost exclusively in Microfarads (μF), Nanofarads (nF), or Picofarads (pF).

A Microfarad is one-millionth of a Farad. This is the standard unit for power-smoothing capacitors found in air conditioners and power supplies (typically ranging from 10 μF to 10,000 μF). Stepping down further, a Nanofarad is one-billionth of a Farad, heavily used in audio filters to block out hums and hisses. The smallest practical unit is the Picofarad, which is one-trillionth of a Farad. Picofarad capacitors are vital for tuning high-frequency radio transmitters and Wi-Fi antennas.

The Capacitor Conversion Trap

Converting between these units mentally is a notorious trap for engineering students and hobbyists. Because they are separated by factors of 1,000, moving a decimal point the wrong way turns a 0.1 μF capacitor into a 100 pF capacitor, completely ruining the frequency response of a circuit. Furthermore, many vintage electronics schematics from the US use outdated jargon, like "mfd" (which actually means microfarad, not millifarad) or "mmfd" (micromicrofarad, an old term for picofarad). Unitomatic's Capacitance Converter provides an ironclad, mathematically perfect translation to ensure you purchase and solder the exact components your schematic demands.