Farads, microfarads, nanofarads, picofarads — decoding capacitor markings
A farad is enormous. Every real capacitor is µF, nF, or pF. Once you can read the three-digit EIA code, every part number becomes obvious.
Capacitance in farads: unrealistic for discrete components. A 1 F capacitor is the size of a small can and stores enough charge to weld metal. Real electronics uses microfarads to picofarads, and each range has its own marking convention.
The exact ladder
1 F = 10⁶ µF = 10⁹ nF = 10¹² pF > 1 µF = 1,000 nF = 10⁶ pF > 1 nF = 1,000 pF > Bulk power supply: 100–10,000 µF (electrolytic) > Decoupling: 0.1 µF = 100 nF (ceramic) > RF tuning: 1–100 pF
The three-digit code
For ceramic caps, three digits mean 'first digit × 10^second digit, in pF'. So '104' = 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. '473' = 47 × 10³ pF = 47 nF. '221' = 22 × 10¹ = 220 pF. Two-digit codes (like '47') are literal in pF. The system is universal across manufacturers.
Ceramic tolerance codes
The letter after the value is the tolerance: J = ±5%, K = ±10%, M = ±20%, Z = +80%/−20% (typical for high-K ceramics used in decoupling). A '104K' cap is 100 nF ±10%. High-K ceramics also drop 30–70% of their capacitance at rated DC bias — a fact that shocks first-time designers.
Worked example — decoupling an MCU
A microcontroller datasheet calls for '0.1 µF decoupling on each power pin'. 0.1 µF = 100 nF = '104' on a ceramic cap marking. Add a 10 µF bulk cap (code 106) for lower-frequency ripple. Total per rail: two caps, ~10 cents. This exact pair appears on essentially every consumer PCB built in the last 30 years.
The five-second recap
1 µF = 1000 nF = 10⁶ pF. Three-digit code: first two × 10^third, in pF. '104' = 100 nF. Letter suffix = tolerance.
Try the converters mentioned in this article
FAQ
What is a supercapacitor?+
A capacitor with capacitance in the farad range (1–3000 F common). Used for backup power and energy buffering; not a drop-in replacement for electrolytics due to low voltage rating (2.5–2.7 V per cell).
Why does my measured capacitance not match the label?+
Ceramic caps lose capacitance under DC bias (up to 70% at rated voltage). Electrolytics have ±20% tolerance and lose capacitance with age. Always measure at the operating voltage.
Is 'MFD' the same as µF?+
Yes — 'MFD' (microfarad) is a legacy US marking, still seen on motor-run capacitors. Modern electronics uses µF.
This article was written by The Turbo Unit Converter engineering desk (Electronics) and last reviewed on 2026-06-30 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.