Takeaway
- Capacitance is measured in Farads (F), but real-world capacitors use three practical sub-units
- picofarads (pF), nanofarads (nF), and microfarads (µF/uF)
- each 1,000 times larger than the last. 1µF = 1,000nF = 1,000,000pF. A capacitor marked “104” decodes to 100,000pF, or 100nF, or 0.1µF
- the industry-standard value for power supply decoupling.
- Getting this conversion wrong is a leading cause of BOM and rework errors.
Why Capacitance Needs Three Different Units
The base SI unit of capacitance is the Farad, named after physicist Michael Faraday. In practice, a full Farad is an enormous amount of charge storage — a 1F capacitor charged to just 1 volt holds roughly the same charge that flows through a 100-watt light bulb in about two seconds. That’s far more capacitance than almost any circuit needs, which is why engineers rarely work in whole Farads at all.
Instead, the electronics industry standardized on three practical fractions of the Farad, each separated from the next by a factor of 1,000:
- Microfarad (µF or uF) = 10⁻⁶ F
- Nanofarad (nF) = 10⁻⁹ F
- Picofarad (pF) = 10⁻¹² F
That thousand-fold spacing isn’t arbitrary — it mirrors the metric prefix system (micro, nano, pico) used throughout science and engineering, so the same logic that governs milliamps and kilohms governs capacitor values too. Once you internalize the ladder — pF, then nF, then µF, each a thousand times bigger — converting between them becomes second nature.
The “u” vs “µ” Question
You’ll often see microfarads written as “uF” instead of “µF,” and both mean exactly the same thing. The substitution dates back to older schematics, printed component labels, and early text-based systems that didn’t support the Greek letter mu (µ) as a standard character. “uF” became the practical stand-in, and it stuck. Occasionally you’ll also encounter “MFD” or “mfd” on vintage or industrial-grade capacitors — that’s an older abbreviation for microfarad, not a typo for millifarad. All of these — µF, uF, and MFD — refer to the identical unit: one-millionth of a Farad.
Doing the Conversion Math
The relationship between the three units follows a simple, consistent rule:
1 µF = 1,000 nF = 1,000,000 pF
That means moving from µF to nF, you shift the decimal three places to the right (multiply by 1,000). Moving from nF to pF, you shift three more places (multiply by another 1,000). So a 0.1µF capacitor is the same physical component as a 100nF capacitor, which is the same as a 100,000pF capacitor — three different ways of writing one identical value.
This is exactly why manufacturers need a compact way to print these values on components that are sometimes smaller than a grain of rice.
How to Read the 3-Digit EIA Marking Code
Ceramic capacitors, especially small surface-mount (SMD) parts, are physically too small to print a full decimal value like “0.1µF.” Instead, manufacturers use a 3-digit code standardized under EIA/IEC conventions:
- The first two digits are the significant figures.
- The third digit tells you how many zeros to add.
- The result is always expressed in picofarads.
Take the earlier example: a capacitor marked “104” breaks down as “10” (significant figures) plus “4” (add four zeros), giving 100,000 pF. Convert that using the 1,000x rule above, and you get 100nF, or 0.1µF — one of the most common values in electronics, used constantly for bypass and decoupling capacitors next to IC power pins.
A two-digit code works differently: there’s no multiplier at all, and the number is a direct picofarad reading. A capacitor marked “47” is simply 47pF — not 470pF, and not 4,700pF. This trips up more engineers than you’d expect, because the eye wants to treat every capacitor code the same way.
There’s also R-notation (sometimes called RKM notation), where the letter R, n, or u stands in for the decimal point to avoid a printing error from a faded or smudged dot. In this system, “4R7” means 4.7pF, and “1n0” means 1.0nF. It’s a clever workaround for a real manufacturing problem: decimal points are the first thing to disappear on low-resolution printing.
Tolerance Codes: The Letter After the Number
Right after the numeric code, you’ll often see a single letter — commonly J, K, or M — indicating the component’s tolerance, or how far the actual capacitance may deviate from the marked value, per EIA/IEC 60062:
| Letter | Tolerance |
| J | ±5% |
| K | ±10% |
| M | ±20% |
A capacitor marked “104K” is a 100,000pF (0.1µF) part with ±10% tolerance. For general-purpose decoupling, ±20% is often perfectly acceptable. For timing circuits or precision analog work, engineers typically specify J or tighter — because a 20% swing in capacitance can visibly shift an RC time constant or filter cutoff frequency.
Why 4.7µF Exists but 5µF Doesn’t
If you’ve ever searched a distributor catalog for a 5µF capacitor and come up empty, you’re not misremembering — it typically doesn’t exist as a standard catalog value. That’s because capacitor values follow the E-series system of preferred numbers, which spaces standard values logarithmically rather than linearly within each decade. This is the same standardized logic used across resistors, inductors, and other passive components, and it’s why you’ll consistently find 1, 1.5, 2.2, 3.3, 4.7, and 6.8 as standard steps — but not 2, 4, or 5. Manufacturers concentrate production on E-series values because spreading tooling and stock across every possible decimal number would be inefficient for everyone in the supply chain.
Matching Unit Range to Application
Different capacitance ranges naturally map to different jobs in a circuit, largely because of how physically large a capacitor needs to be to store that much charge:
pF range — RF and tuning circuits. Single and double-digit picofarad capacitors show up in oscillators, filters, and impedance-matching networks, where tiny, precise capacitance values shape high-frequency behavior. Ceramic C0G/NP0 dielectrics and mica types dominate here for their stability over temperature.
nF range — timing and coupling. Nanofarad-range capacitors are the workhorses of RC timing circuits, debounce networks, and signal coupling between amplifier stages, where they block DC while passing AC. X7R ceramic and film dielectrics are common choices.
µF range — bulk storage and power filtering. From the ubiquitous 0.1µF decoupling cap parked next to nearly every IC’s power pins, up through hundreds or thousands of microfarads in electrolytic capacitors used for power supply rectification and ripple smoothing, this is the range associated with real energy storage. Electrolytic and tantalum types dominate at the higher end, and — unlike most pF/nF ceramic parts — they’re frequently polarized, meaning orientation matters when you solder them in.
Reading Larger Capacitors
Not every capacitor relies on cryptic 3-digit codes. Larger electrolytic and tantalum capacitors typically have enough physical surface area to print the value directly, along with a voltage rating — something like “47µF 25V” printed right on the can. This removes the decoding step entirely wherever package size allows it, which is one reason larger capacitors are generally easier to identify at a glance during rework or field repair than their tiny SMD cousins.
That said, compact 0402 and 0603 SMD packages frequently carry no printed marking at all — there simply isn’t room. For those, engineers commonly rely on an LCR meter for incoming verification, or strict BOM and reel-label traceability, rather than trying to read a value off the part itself.
A Quick Reference Table
| Attribute | pF Range | nF Range | µF Range |
| Typical technology | Ceramic (C0G/NP0), mica | Ceramic (X7R), film | Electrolytic, tantalum, larger ceramic |
| Common marking | 2-digit direct or 3-digit EIA code | 3-digit EIA code or “n” notation | Direct printed value (“47µF 25V”) |
| Typical application | RF, oscillators, tuning | Timing, coupling, filtering | Power filtering, bulk storage |
| Polarity | Non-polarized | Non-polarized | Often polarized (electrolytic/tantalum) |
| Example marking | “47” = 47pF | “473” = 47,000pF = 47nF | “106” = 10,000,000pF = 10µF |
Sourcing and Manufacturing Notes
Capacitors spanning the full pF-to-µF range are broadly available from stock across ceramic, film, tantalum, and electrolytic technologies, with prototype-friendly small quantities alongside cut-tape or reel packaging for automated SMT lines. For unusual capacitance, voltage, or tolerance combinations, most distributors offer engineering support to source custom values or suggest the nearest E-series alternative. Standard lead times range from same-day availability for common E-series stock values to several weeks for tightly toleranced or high-voltage custom parts — worth factoring in early if your design calls for anything outside the standard catalog.
Frequently Asked Questions
How many pF are in 1µF?
1µF equals 1,000,000pF. The conversion follows the standard 1,000x step between each unit: 1µF = 1,000nF = 1,000,000pF, so you can move between any two units by shifting the decimal point three places per step.
What does the capacitor code “104” mean?
It’s a 3-digit EIA code: the first two digits (10) are the significant figures, and the third digit (4) means “add four zeros.” The result, 100,000pF, equals 100nF or 0.1µF — the standard value used for bypass and decoupling capacitors across most digital and analog circuits.
Why is “uF” sometimes written instead of “µF”?
Older schematics, printed labels, and text-only systems that lack the Greek mu (µ) character substitute “u” as a readable equivalent, so “uF,” “µF,” and occasionally “mfd” or “MFD” all refer to the same microfarad unit — there’s no functional difference.
How do I read a two-digit capacitor code like “47”?
Two-digit codes represent the value directly in picofarads with no multiplier applied — “47” means 47pF, not 470pF or 4,700pF. This is a different rule from the 3-digit EIA code, which is where mix-ups most often happen.
Why can I buy a 4.7µF capacitor but not a 5µF capacitor?
Capacitor values follow the E-series system of preferred numbers, which spaces standard values logarithmically within each decade instead of counting in whole numbers. 4.7 is a standard E-series step; 5 is not, so manufacturers don’t produce or stock it as a catalog value.
Getting It Right the First Time
Capacitance unit confusion is preventable once the 1,000x ladder between pF, nF, and µF becomes automatic, and once you know which decoding rule applies to which marking — direct pF for two digits, multiplier-based pF for three digits, decimal substitution for R-notation. That small bit of fluency pays off directly in BOM accuracy, faster prototype debugging, and fewer wrong parts pulled during field repair.
Find What You Need on LCSC
Whether your design calls for a pF-range NP0 ceramic for an RF filter or a bulk µF-range electrolytic for power smoothing, LCSC stocks the full capacitance spectrum from leading manufacturers, with clear datasheets, verified specifications, and real-time stock availability so you’re never guessing at a marking code. Filter by capacitance, voltage rating, tolerance, and dielectric type to find the exact part your BOM calls for, from same-day-shippable E-series values to harder-to-source custom specifications. For engineers and procurement teams who need components fast and right the first time, LCSC’s searchable catalog and detailed technical parameters take the guesswork out of sourcing — so you can spend less time decoding capacitor markings and more time building.
