Master capacitor units — pF, nF, and µF — with easy conversion tables, 3-digit code reading, and real PCB design tips from an engineer’s perspective.
If you’ve spent any time working with electronics, you’ve inevitably stared at a capacitor datasheet and wondered whether 0.1µF and 100nF are actually the same thing. Spoiler: they are. But when you’re knee-deep in a PCB layout and cross-referencing BOM values with component datasheets, those unit mismatches can cause real confusion — and real mistakes.
Understanding capacitor units isn’t just academic. It directly affects how you read datasheets, how you order components, and how you verify your circuit is built correctly. In this guide, I’ll walk you through every unit you’ll encounter, how to convert between them confidently, and how to avoid the common errors that trip up beginners and intermediate engineers alike.
Why Capacitor Units Matter in Real PCB Work
Before jumping into the math, let me make the case for why this matters practically. When you’re placing a capacitor on a PCB, the value printed on the schematic has to match what’s in your BOM, which has to match what’s on the component you physically solder down. A 10pF cap and a 10nF cap are not interchangeable — that’s a 1000× difference. In an RF filter, swapping those two would completely destroy the circuit’s frequency response.
Distributor databases like Digi-Key and Mouser let you search by capacitance value, but they don’t always standardize units — you might see the same component listed as 0.01µF, 10nF, or 10,000pF depending on the manufacturer’s datasheet. If you can’t quickly recognize that all three are identical, you’re going to waste time and risk sourcing errors.
The Base Unit: What Is a Farad?
The Farad (F) is the SI unit of capacitance, named after Michael Faraday. One Farad is defined as the capacitance of a capacitor that stores one coulomb of charge when one volt is applied across its terminals.
In practice, one Farad is an enormous amount of capacitance. A 1F capacitor is a supercapacitor — a physically large, specialized component used in energy storage applications. The capacitors you work with day-to-day on PCBs are a tiny fraction of a Farad, which is why we use smaller sub-units for virtually everything in standard circuit design.
The Three Main Capacitor Units You’ll Use Every Day
Microfarad (µF) — The Workhorse for Power Circuits
The microfarad (µF) is one millionth of a Farad:
1 µF = 0.000001 F = 10⁻⁶ F
This is the most common unit you’ll see for electrolytic and tantalum capacitors. Power supply bulk capacitors, audio coupling caps, and voltage regulator bypass caps are almost always specified in µF. You’ll regularly encounter values from 0.1µF up to 10,000µF or more in power electronics.
The µ symbol (Greek letter mu) is sometimes written as “u” in ASCII contexts where the special character isn’t available — so “10uF” and “10µF” mean exactly the same thing. You’ll see both in datasheets and schematics.
Nanofarad (nF) — The Middle Ground
The nanofarad (nF) is one billionth of a Farad:
1 nF = 0.000000001 F = 10⁻⁹ F
The nanofarad sits between µF and pF. It’s commonly used for ceramic capacitors in filter circuits, timing networks, and signal coupling. Values like 10nF, 100nF, and 220nF appear constantly in general-purpose circuit design. Interestingly, many US-based schematics skip nF entirely and express these values in µF or pF instead — a habit that causes endless unit-matching headaches.
Picofarad (pF) — For RF and High-Frequency Work
The picofarad (pF) is one trillionth of a Farad:
1 pF = 0.000000000001 F = 10⁻¹² F
Picofarads are the territory of RF circuits, oscillator load capacitors, impedance matching networks, and parasitic capacitance calculations. Crystal oscillator circuits typically use load capacitors in the 6pF–22pF range. Antenna matching networks work in single-digit picofarads. At these tiny values, even the parasitic capacitance of a PCB trace (typically 0.5–2pF per cm) becomes significant.
Full Capacitor Unit Reference Table
Here’s a complete reference for all capacitance units you might encounter, from largest to smallest:
| Unit | Symbol | Power of 10 | Equivalent in Farads | Common Use Case |
| Farad | F | 10⁰ | 1 F | Supercapacitors, reference unit |
| Millifarad | mF | 10⁻³ | 0.001 F | Rarely used; supercap spec sheets |
| Microfarad | µF (uF) | 10⁻⁶ | 0.000001 F | Power supply caps, electrolytics |
| Nanofarad | nF | 10⁻⁹ | 0.000000001 F | General ceramic caps, filters |
| Picofarad | pF | 10⁻¹² | 0.000000000001 F | RF, oscillators, high-freq circuits |
Capacitor Unit Conversion: The Definitive Chart
This is the table I wish I’d had when I started doing PCB layout. Bookmark it.
Converting Between µF, nF, and pF
| To Convert | Multiply By | Example |
| µF → nF | × 1,000 | 0.1µF = 100nF |
| µF → pF | × 1,000,000 | 0.001µF = 1,000pF |
| nF → µF | ÷ 1,000 | 47nF = 0.047µF |
| nF → pF | × 1,000 | 4.7nF = 4,700pF |
| pF → nF | ÷ 1,000 | 10,000pF = 10nF |
| pF → µF | ÷ 1,000,000 | 100,000pF = 0.1µF |
The Most Common Equivalent Values — All Three Units Side by Side
This is where engineers lose time most often. Here’s a cheat sheet covering the values you’ll see most frequently in real designs:
| pF | nF | µF | Common Application |
| 10 pF | 0.01 nF | 0.00001 µF | Crystal load cap, RF matching |
| 100 pF | 0.1 nF | 0.0001 µF | RF decoupling, EMI filter |
| 1,000 pF | 1 nF | 0.001 µF | General filter, snubber |
| 10,000 pF | 10 nF | 0.01 µF | Gate drive, bypass |
| 100,000 pF | 100 nF | 0.1 µF | IC decoupling (most common) |
| 1,000,000 pF | 1,000 nF | 1 µF | Bulk decoupling, audio coupling |
| 10,000,000 pF | 10,000 nF | 10 µF | Power supply filtering |
| 100,000,000 pF | 100,000 nF | 100 µF | Bulk storage, motor drives |
Pay special attention to 100nF = 0.1µF — this is the single most commonly used decoupling capacitor value in all of digital electronics, and you’ll see it expressed both ways depending on who drew the schematic.
How to Read Capacitor Codes and Convert Them
The 3-Digit Code System
Small ceramic capacitors — especially SMD types — rarely have the value printed in a human-readable format. Instead, they use a 3-digit code where the result is always in picofarads (pF).
The rule: first two digits are the value, third digit is the multiplier (number of zeros)
| Code | Calculation | Value in pF | Converted |
| 101 | 10 × 10¹ | 100 pF | 0.1 nF |
| 102 | 10 × 10² | 1,000 pF | 1 nF |
| 103 | 10 × 10³ | 10,000 pF | 10 nF / 0.01 µF |
| 104 | 10 × 10⁴ | 100,000 pF | 100 nF / 0.1 µF |
| 105 | 10 × 10⁵ | 1,000,000 pF | 1 µF |
| 220 | 22 × 10⁰ | 22 pF | 22 pF |
| 472 | 47 × 10² | 4,700 pF | 4.7 nF |
| 333 | 33 × 10³ | 33,000 pF | 33 nF |
The “9” multiplier is a special case — it means × 10⁻¹, so a code of “229” means 22 × 0.1 = 2.2 pF.
Tolerance Codes
Capacitors often carry a letter after the 3-digit code to indicate tolerance:
| 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 precision filter and timing circuits, you want J (±5%) or better. For bulk bypass and power supply caps, K or M is usually fine.
Understanding Capacitor Unit Notation in Datasheets and Schematics
One source of genuine confusion is that different regions and different companies use different notation conventions.
European notation often uses the unit prefix as a decimal point. So “4n7” means 4.7nF and “2p2” means 2.2pF. You’ll see this on older component markings and European-sourced datasheets. “1µ0” means 1.0µF.
American notation tends to write values with explicit decimal points and full unit symbols: 4.7nF, 2.2pF, 1.0µF.
Some older US schematics express everything in µF with scientific notation: 1×10⁻⁴ µF instead of 100pF, or skip nF entirely and jump from pF to µF. This is why a 0.01µF capacitor can appear in datasheets, schematics, and BOMs as 0.01µF, 10nF, or 10,000pF — all simultaneously correct.
Practical Conversion Tips From PCB Design Work
Mental math shortcut: Moving between µF, nF, and pF is always a factor of 1,000. So every time you step down one unit (µF → nF → pF), multiply the number by 1,000. Every time you step up (pF → nF → µF), divide by 1,000.
When checking your BOM: Always normalize all capacitance values to the same unit before comparing. I use pF as the base when working on RF designs, and µF when working on power electronics. Pick one and convert everything to it.
Watch out for mF: Millifarads (10⁻³ F) appear on some supercapacitor spec sheets but are almost never used in standard circuit design. Don’t confuse mF (millifarad) with µF (microfarad) — that’s a 1,000× error.
Useful Resources for Capacitor Unit Conversion and Component Selection
| Resource | Type | What It’s Good For |
| Digi-Key Capacitor Search | Component Database | Parametric search by value, voltage, package |
| Mouser Capacitor Selector | Component Database | Cross-reference and filter by specs |
| Murata SimSurfing | Simulation Tool | Frequency response of real ceramic caps |
| TDK Product Finder | Datasheet Library | Detailed specs including ESR, temperature curves |
| KEMET Capacitor Finder | Product Database | Filter by dielectric, voltage, capacitance |
| Vishay Capacitor Catalog | Datasheet Library | Film and ceramic capacitor selection |
| All About Circuits – Capacitors | Educational | Deep technical background |
| IPC-2221 Standard | Design Standard | PCB design rules including component placement |
Frequently Asked Questions About Capacitor Units
1. Is 0.1µF the same as 100nF?
Yes, exactly the same. 0.1µF = 100nF = 100,000pF. This is the most common decoupling capacitor value in digital circuit design, and you’ll see it written all three ways depending on the source. When in doubt, convert everything to pF and compare the raw numbers.
2. What does “uF” mean on a capacitor?
“uF” is the ASCII substitute for “µF” (microfarad). Because the Greek letter µ (mu) isn’t available on standard keyboards, many manufacturers, datasheets, and software tools use “u” as a substitute. So 10uF and 10µF are identical — both mean 10 microfarads.
3. How do I convert nF to µF quickly?
Divide by 1,000. So 470nF ÷ 1,000 = 0.47µF. Going the other direction (µF to nF), multiply by 1,000: 0.047µF × 1,000 = 47nF. The factor between any two adjacent units (pF↔nF, nF↔µF, µF↔mF) is always 1,000.
4. Why do some schematics skip nF and go straight from pF to µF?
This is a legacy convention, particularly common in older American engineering documentation. Designers would express values under 1,000pF in pF, and everything above in µF — completely skipping the nF unit. So a 10,000pF cap would be written as 0.01µF rather than 10nF. Both are correct; the convention just varies by region and era.
5. Does the unit affect which type of capacitor I should use?
Not directly — the unit is just a way of expressing the capacitance value. However, in practice there’s a strong correlation: pF-range caps are almost always ceramic (C0G/NP0 for precision RF), nF-range caps are usually ceramics (X7R, X5R), and µF-range caps can be ceramic (for small values like 1–10µF) or electrolytic/tantalum (for larger values). The full spec — including voltage rating, dielectric type, ESR, and package — comes from the datasheet, not just the capacitance value.
Final Thoughts
Getting capacitor units right is one of those foundational skills that pays dividends every time you sit down to read a datasheet, build a BOM, or debug a circuit. The math is simple once you internalize that each step between pF, nF, and µF is exactly 1,000×. The conversion table and code-reading guide in this article should cover 95% of everything you’ll encounter in real PCB design work.
The other 5% — exotic units like mF, or the European decimal-substitution notation — is easy enough to handle once you know it exists. Now you do.
