Electronics · Math shelf · Optional — for the curious · build 2026.09.23-1644
The idea
Electronics spans absurd ranges — millionths of a volt to millions of ohms. Prefixes keep the numbers human: every step is exactly ×1,000.
Power shorthand
The numbers below get too big for commas, so they wear exponents: 10⁹ means a 1 with 9 zeros (1,000,000,000). Every three zeros is one rung of the ladder.
| Prefix | Say it | Means | Where you'll meet it |
|---|---|---|---|
| Z | zetta | × 10²¹ — a sextillion | ZB — a whole year of the entire internet's traffic |
| E | exa | × 10¹⁸ — a quintillion | exaflops — the fastest supercomputers' calculations per second |
| P | peta | × 10¹⁵ — a quadrillion | PB — a data center's storage |
| T | tera | × 10¹² — a trillion | TB — big hard drives |
| G | giga | × 10⁹ — a billion | GB, GHz — your phone's storage, and its processor's clock |
| M | mega | × 10⁶ — a million | MΩ — your hand-to-hand resistance; MB — a photo |
| k | kilo | × 10³ — a thousand | kΩ — the 1 k, 4.7 k, 10 k resistors; km — road signs |
| — | (plain) | × 1 — one | V, Ω, A |
| c | centi | ÷ 100 — a hundredth | cm — rulers everywhere; the odd one out (a half-rung — see below) |
| m | milli | ÷ 10³ — a thousandth | mV, mA — LED currents live here; mm |
| µ | micro (Greek "mu") | ÷ 10⁶ — a millionth | µF — capacitors, coming soon; µm — a bacterium is a few of these |
| n | nano | ÷ 10⁹ — a billionth | nF — mid-size capacitors; nm — your phone chip's transistors |
| p | pico | ÷ 10¹² — a trillionth | pF — the smallest capacitors are labeled in these |
| f | femto | ÷ 10¹⁵ — a quadrillionth | fs — laser pulses quick enough to photograph chemistry happening |
| a | atto | ÷ 10¹⁸ — a quintillionth | as — clocking electrons in motion won the 2023 Nobel Prize in physics |
The half-rung
Centi (÷100) isn't on the ladder — it's half a rung, a survivor from metric's early days. Engineering sticks to full ×1,000 steps (your meter will never say "cV"), but centimeters are too woven into daily life to retire. Its cousins deci (÷10) and hecto (×100) survive in a few corners too — deciliters on drink bottles, hectares for land — and nowhere in electronics.
Case matters — a lot
Capital M is mega; lowercase m is milli. They differ by a factor of a billion. Worse still: capital P (peta) and lowercase p (pico) differ by a factor of a billion billion billion. Writing one for the other is among the most expensive typos in engineering — always copy the letter exactly as the meter or the label shows it.
Each rung moves the decimal point three places. Down the ladder to a smaller unit, the number grows; up to a bigger unit, it shrinks:
The display only has about four digits, so the meter (and every engineer) picks the prefix that lands the number between 1 and 999. Nobody writes 4,700 Ω or 0.014 A; they write 4.7 kΩ and 14 mA. When the meter's reading crosses 1,000, it just hops up the ladder — the resistor didn't change, only its clothes did.
Answers at the bottom.
1. 0.22 kΩ (and now you see why nobody writes it that way). 2. 1,234 Ω. 3. 0.5 V = 500 mV, so 0.5 V wins. 4. 850 kΩ = 850,000 Ω. 5. 0.1 µF — one rung up the ladder. 6. 2,000 GB = 2,000,000 MB — one rung down, then another ×1,000.