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Resistor colour code and SMD code calculator
Both directions: pick the bands or type the mark to read a value; type a value to get the bands and every SMD marking it can carry.
The formula
4 band: d1 d2 × multiplier ± tol 5 band: d1 d2 d3 × multiplier ± tol EIA-96: E96 index (01–96) + multiplier letter
When to use it
Reading a through-hole part on a legacy board, checking a reel against the BOM, or labelling a drawer. SMD marks are the trap: a 3-digit mark reads as two digits and a multiplier, a 4-digit mark as three and a multiplier, and an EIA-96 mark is two digits and a letter where the digits are a table index, not a value — 01C is 10 kΩ, not 1 kΩ.
Pitfalls
- Read the bands from the end where they sit closest to the edge; the tolerance band is usually spaced apart. Gold and silver are never a first digit.
- Many small SMD resistors (0402 and below) carry no mark at all. The only reliable record is the BOM and the reel label.
- An R in an SMD mark is the decimal point: 4R7 is 4.7 Ω, R47 is 0.47 Ω. A lone 0 or 000 is a jumper.
- EIA-96 letters: Z ×0.001, Y or R ×0.01, X or S ×0.1, A ×1, B or H ×10, C ×100, D ×1 k, E ×10 k, F ×100 k.
Reading a board you didn’t design? We reverse-engineer and redraw it.