Resistor code

Work out the resistance from the 3-digit code printed on a chip resistor. Example: 103 = 10 kΩ

Code

Resistance

1kΩ

History

Press Enter in any field to keep a snapshot here.

Formula

Formula: first two digits × 10^(third digit) [Ω]
Example: 103 → 10 × 10³ Ω = 10 kΩ

Design notes

Chip resistors are marked with a three-digit code (four digits on precision parts). Even when the print on a small chip is hard to read, the code tells you the value straight away.

Codes you will see often:
• 103 → 10 kΩ (dividers and pull-ups)
• 472 → 4.7 kΩ (LED current limiting)
• 331 → 330 Ω
• 000 → 0 Ω (a jumper)

When you need this

For reading the marking on a chip resistor, or turning a three-digit code into a resistance. Unlike capacitors, resistors are marked, so they are one of the few parts you can identify from the board itself.

Reading the three-digit code

The first two digits are the significant figures and the third is the number of zeros. The unit is Ω.

"102" is 10 followed by two zeros: 1,000Ω = 1kΩ. "472" is 47 followed by two zeros: 4,700Ω = 4.7kΩ. The rule matches capacitors; only the base unit is Ω rather than pF.

Common values

Code	Resistance	Typical use
100	10 Ω	Damping, supply filtering
220	22 Ω	Standard damping value
330	33 Ω	Standard damping value
101	100 Ω	General purpose
221	220 Ω	LED current limiting
102	1 kΩ	General purpose, pull-up
472	4.7 kΩ	The standard I²C pull-up
103	10 kΩ	The standard pull-up/pull-down
104	100 kΩ	Weak pull-up
105	1 MΩ	Bleed paths, high impedance

Other markings

Codes containing "R". "4R7" is 4.7Ω and "R47" is 0.47Ω, with R as the decimal point. Common on current-sense resistors.
Four-digit codes (±1% parts). Three significant figures plus a zero count. "4701" is 470 followed by one zero: 4,700Ω = 4.7kΩ. Used for E96 values.
EIA-96 codes. Parts 0603 and smaller use three-character codes such as "01A": two digits index the E96 series and the letter is the multiplier. You need a lookup table.
"000" or "0". A zero-ohm jumper, used to configure the board through the layout.

Know the E series

Resistance values are not continuous; they come from the E series. E24 (24 values per decade, for ±5%) and E96 (96 values, for ±1%) are the common ones.

You cannot order the ideal value your calculation produced, so you must re-check the design with the E-series value you will actually buy. Rounding to E24 introduces up to about 2% error.

E24: 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91 — each multiplied by a power of ten.

Frequently asked questions

Is "103" 103Ω?

No, it is 10kΩ. The first two digits "10" are the significant figures and the third digit "3" is the number of zeros, giving 10,000Ω. Reading it literally as 103 is a common error.

What are zero-ohm resistors for?

Reconfiguring a board after layout: option settings, enabling circuit variants, and jumping across traces. Unlike a wire link, a machine can place them like any other component. The resistance is not truly zero — expect tens of milliohms.

How do I read colour bands?

That marking is used on leaded resistors. Four bands are two significant figures, a multiplier and a tolerance; five bands are three significant figures, multiplier and tolerance. Black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, grey=8, white=9. This calculator handles numeric codes only.

Why such odd numbers in E24?

They are spaced logarithmically. E24 divides a decade into 24 steps, so adjacent values differ by 10^(1/24) ≈ 1.101, roughly 10%. With ±5% tolerance that spacing covers every value with no gaps. E96 is for ±1% and steps by about 2.4%.

Standards and references

IEC 60062 — Marking codes for resistors and capacitors.
IEC 60063 — Preferred number series (E6 / E12 / E24 / E96).
IEC 60115-1 — Generic specification for fixed resistors.

Last updated: 2026-08-29