Metric Prefixes: Pico to Giga
The base units of electronics — the farad, the henry, the ohm, the ampere, the hertz — were defined at sizes that are either far too large or far too small for the components and signals you actually work with. The metric prefix system solves this by attaching standard multipliers to those base units, producing convenient-sized quantities like picofarads, kilohms and megahertz. Knowing these prefixes fluently, without a lookup table, is one of the most practical skills you can develop as an electronics learner.
The Problem of Range
The base units in electronics were defined at scales that are either far too large or far too small for practical components.
A 1-farad capacitor is a very large component (they exist but they weigh kilograms and are used for energy storage, not signal circuits). A typical signal capacitor is around one millionth of a millionth of a farad — 1 picofarad. A 1-henry inductor is a large, heavy coil; most RF inductors are measured in nanohenries. A 1-ohm resistor is barely a resistor at all in most signal circuits; you routinely encounter megaohms (millions of ohms). The base unit for frequency — 1 hertz — is one cycle per second; a standard 2 m transceiver operates at 144 million hertz.
Rather than writing 0.000000000001 farads every time, electronics uses a system of standard prefixes that attach to the base unit and carry the scaling information. Once you know the prefixes, a value like 47 nH tells you everything you need instantly.
The Full Prefix Table
| Prefix | Symbol | Power of 10 | Decimal | Electronics example |
|---|---|---|---|---|
| pico | p | 10−12 | 0.000000000001 | 100 pF capacitor |
| nano | n | 10−9 | 0.000000001 | 100 nH inductor |
| micro | μ | 10−6 | 0.000001 | 10 μF capacitor |
| milli | m | 10−3 | 0.001 | 500 mA fuse |
| (base unit) | — | 100 | 1 | 50 Ω coax |
| kilo | k | 103 | 1,000 | 4.7 kΩ resistor |
| mega | M | 106 | 1,000,000 | 14.2 MHz (HF) |
| giga | G | 109 | 1,000,000,000 | 2.4 GHz (Wi-Fi) |
The prefix tera (T, 1012) is not commonly used in ham radio but appears in some digital communications contexts such as data transfer rates in fiber optic systems.
Electronics Examples for Each Prefix
Pico (p, 10−12)
The smallest prefix you will regularly use in electronics. Small capacitors in RF circuits are routinely in the range of 5 pF to 1000 pF. Crystal stray capacitances are often just a few pF. Varactor diodes have capacitances of 5–100 pF that vary with applied voltage, allowing them to tune resonant circuits. The matching capacitor in a 14 MHz antenna matching network might be around 100 pF.
Nano (n, 10−9)
RF inductors are typically in the nanohenry range — a 100 nH coil is a small, low-inductance component used in VHF and UHF circuits. Capacitors in the range 1 nF to 999 nF are also common, though these are often written as pF (1 nF = 1000 pF) or μF (1 nF = 0.001 μF) depending on context. A 10 nF decoupling capacitor on a logic IC supply pin is a typical value.
Micro (μ, 10−6)
Electrolytic capacitors for power supply filtering and decoupling are usually in the 10–10,000 μF range. Coupling and bypass capacitors in audio circuits are often 0.1–10 μF. Inductors in the range 1–1000 μH are used in RF filters, matching networks and switching power supplies.
Milli (m, 10−3)
Current in small-signal circuits is often measured in milliamps. A typical transistor collector current might be 2–50 mA. Milliwatts (mW) appear in signal level specifications: the 0 dBm reference level is exactly 1 mW. A QRP transmitter might produce 5 W (5000 mW) output.
Base unit
At the base unit level you find values like 50 Ω (coaxial cable characteristic impedance), 1 A (current through a logic IC power pin), 5 V (digital logic supply), 13.8 V (standard ham radio shack supply voltage).
Kilo (k, 103)
Resistors are most commonly in the kilohm range: 1 kΩ, 4.7 kΩ, 100 kΩ. Frequencies in the LF and MF range are in kilohertz — AM broadcast radio occupies 500–1600 kHz. The 160 m amateur band runs from 1800 to 2000 kHz.
Mega (M, 106)
HF radio frequencies are in megahertz: 3.5 MHz (80 m), 7 MHz (40 m), 14 MHz (20 m), 21 MHz (15 m), 28 MHz (10 m). High-value resistors in oscillator bias circuits are often in the megaohm range: 1 MΩ, 10 MΩ. Bandwidth specifications for equipment are sometimes in MHz.
Giga (G, 109)
VHF frequencies climb into the lower gigahertz. The 23 cm amateur band is at 1240–1300 MHz = 1.24–1.3 GHz. Wi-Fi at 2.4 GHz and 5 GHz, Bluetooth at 2.4 GHz, and microwave links all use gigahertz frequencies. Modern transceivers and SDR receivers often specify their upper frequency limit in GHz.
Converting Between Prefixes
Each step up the prefix table is a factor of 1000 (103). This is the single most important fact to know about metric prefixes.
Going from a smaller prefix to a larger prefix: divide by 1000 per step.
Going from a larger prefix to a smaller prefix: multiply by 1000 per step.
pico ↔ nano ↔ micro ↔ milli ↔ base ↔ kilo ↔ mega ↔ giga
×1000 each step down ÷1000 each step up
Worked examples:
- 4700 nF → μF: one step up → ÷ 1000 → 4.7 μF
- 0.022 μF → nF: one step down → × 1000 → 22 nF
- 100 MHz → kHz: two steps down → × 1000 × 1000 = × 106 → 100,000 kHz
- 1500 kHz → MHz: one step up → ÷ 1000 → 1.5 MHz
- 47 kΩ → Ω: one step down → × 1000 → 47,000 Ω
pF to nF is one step up the prefix ladder (pico is smaller than nano).
Going up one step means divide by 1000.
330 ÷ 1000 = 0.33 nF
Answer: 330 pF = 0.33 nF
Step-Up and Step-Down Conversion
For multi-step conversions, count the number of prefix steps between source and destination, then multiply or divide by 103 per step (which is the same as multiplying or dividing by 10(3 × steps)).
10,000 pF = 10,000 ÷ 1,000,000 μF = 0.01 μF
GHz to MHz (one step down): multiply by 103
2.4 GHz = 2.4 × 1000 MHz = 2400 MHz
Safe alternative for any conversion:
Convert to base unit first (multiply or divide by the source prefix value), then convert to target prefix.
Example: 47 nH to μH
47 nH = 47 × 10−9 H (base) = 47 × 10−9 ÷ 10−6 μH = 47 × 10−3 μH = 0.047 μH
The Metric Prefix Converter
Enter any value and select its prefix. The converter shows the equivalent in all prefixes from pico to giga.
Metric Prefix Converter
Enter a value and select its prefix. The converter shows the equivalent in all prefixes from pico to giga.
Common Mistakes
m = milli (10−3), M = mega (106). A 10 MΩ resistor and a 10 mΩ resistor differ by a factor of 109 — a billion times. Always check case when reading or writing prefix symbols.
μ is the Greek letter mu; m is lower-case Latin m for milli. On circuit boards and datasheets, μ is sometimes written as u (since μ is not on a standard keyboard) — 4u7 means 4.7 μF, not 4.7 mF. Some manufacturers also write 4R7 for a 4.7-ohm resistor (R marks the decimal point position). These notations are common enough that you should recognize them, but always use the correct μ symbol in your own written work.
When converting pF to μF directly, it is easy to get the factor wrong. Count the steps explicitly: pF → nF = ÷1000, nF → μF = ÷1000, so pF → μF = ÷106. Alternatively, convert via the base unit as a safety check.
A 50 kΩ resistor is 50,000 ohms. If you need it in Ohm's Law (V = IR), you must enter 50,000 (or 50 × 103), not 50. Forgetting to convert prefixed values to base units before substituting into a formula is the most common source of error in simple calculations.
The metric prefix system from pico (10−12) to giga (109), showing the factor-of-1000 steps between adjacent prefixes.
View LargerFrequently Asked Questions
Why does the metric prefix table skip some powers of 10?
Standard SI metric prefixes step in factors of 1000 (103), not 10. So the standard sequence is pico (10−12), nano (10−9), micro (10−6), milli (10−3), base (100), kilo (103), mega (106), giga (109). The prefixes centi (10−2) and deci (10−1) exist in the SI system (used in centimetres and deciliters) but are essentially never used in electronics — you will never see a "centifarad." The reason the system skips by 1000 is that it maps to engineering notation, which uses exponents that are multiples of 3, which in turn matches the visual chunking of digits into groups of three (1,000,000 vs 1000000). This makes the numbers easier to read and directly corresponds to the metric prefix.
Why is micro written as μ and not u?
μ is the Greek letter mu, the SI standard symbol for micro. It is correct to write μF (microfarad), μH (microhenry), μA (microamp). Because μ is not available on a standard ASCII keyboard, it is often substituted with the letter u in schematics, circuit boards, datasheets and computer input. You will see 100u on a capacitor footprint meaning 100 μF, or 4u7 meaning 4.7 μF. Some manufacturers also write 4R7 for a 4.7-ohm resistor (R as the decimal point position marker). These notations are common enough that you should recognize them, but always use the correct μ symbol in your own written work.
What is the difference between kB and KB in data?
While not strictly an electronics question, this distinction matters if you work with digital systems. In SI metric, kilo always means exactly 1,000. In computing, however, "KB" traditionally meant 1024 bytes (210) because computer memory is binary. Modern standards resolve this: kB = 1,000 bytes (SI kilo); KiB (kibibyte) = 1,024 bytes (binary). In radio engineering, frequencies and signal levels always use SI metric exactly — 14 MHz is exactly 14,000,000 Hz, not 14 × 10242 Hz. The confusion only arises in data storage and data rate contexts.
Test Your Knowledge
Answer the questions below to check your understanding of this lesson. Every answer can be found in the lesson above.