Resistor Color Code Calculator
Decode 4- and 5-band resistor colour codes, encode a value back into bands, and translate between SMT markings (3-digit, 4-digit, EIA-96, R-notation) and resistance.
Resistance
470 Ω
±5%
Nearest preferred value
- E12 (±10%)470 Ω✓ exact
- E24 (±5%)470 Ω✓ exact
How resistor colour codes work
Each colour band encodes a digit or multiplier from a fixed table. A 4-band resistor uses two significant digits + multiplier + tolerance. A 5-band resistor adds a third significant digit for precision parts (±1 % or tighter).
Reading a 4-band code
- Band 1 — first significant digit
- Band 2 — second significant digit
- Band 3 — multiplier (×10ⁿ)
- Band 4 — tolerance (Gold = ±5 %, Silver = ±10 %)
SMT markings
Switch to the SMT tabs above to decode chip markings (3-digit, 4-digit, EIA-96, R-notation).
E-series preferred values
Resistors are manufactured only in standard preferred values — E12 (12 per decade, ±10 %) and E24 (24 per decade, ±5 %). The "Nearest preferred value" hint shows the closest available off-the-shelf part for any value you enter.
Quick experiments
- Read the classic 470 Ω. Yellow-Violet-Brown-Gold decodes as 4, 7, then ×10, giving 470 Ω at ±5 %. Change the third band to Red and the same first two digits become 4.7 kΩ — the multiplier band is the only thing that moved.
- Watch precision cost you a band. Brown-Black-Black-Red-Brown is 10 kΩ at ±1 %. Five-band parts spend an extra band on a third significant digit, which is why 1 % resistors can hit values like 4.99 kΩ that no 4-band part can express.
- Decode surface-mount. Switch to the SMT tab and enter
103— 10 followed by three zeros, so 10 kΩ. Then try4R7: the R stands in for the decimal point, giving 4.7 Ω. Codes below 10 Ω almost always use it. - Go backwards. Use Value → Color with 2.2 kΩ. You will get Red-Red-Red, which is worth memorising — the repeated band is a useful sanity check when you are squinting at a real part.
Resistor color code — reference
The colour bands encode a number in scientific notation. Each colour maps to a digit: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. Read them from the end where the bands are crowded together — the tolerance band sits alone at the far end, usually gold or silver.
Four bands versus five
A four-band resistor spends two bands on significant digits, one on the power-of-ten multiplier, and one on tolerance. A five-band part adds a third significant digit, which is what lets tight-tolerance resistors express values the E24 series cannot. A rare sixth band gives the temperature coefficient in ppm/°C.
Why the values look arbitrary
Values are not evenly spaced — they follow the E-series, which spaces them logarithmically so that consecutive values differ by roughly the tolerance. E12 (10 %) gives 12 values per decade: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82. E24 (5 %) gives 24. That is why 4.7 kΩ is everywhere and 5 kΩ is not — a 5 kΩ part would overlap its neighbours once tolerance is applied.
Surface-mount codes
SMT resistors are printed rather than banded. Three-digit codes give two significant digits and a multiplier (472 = 4.7 kΩ). Four-digit codes give three (4701 = 4.7 kΩ, more precisely). An R marks a decimal point for sub-10 Ω parts. The EIA-96 system on very small packages uses two digits plus a letter, where the digits index a lookup table rather than reading directly as a value.
Tolerance and what it means in practice
Gold is ±5 %, silver ±10 %, brown ±1 %, red ±2 %. Tolerance matters where the resistor sets a ratio you care about — an op-amp gain network or a voltage divider feeding an ADC — and matters far less for a pull-up or an LED series resistor, where anything in the right decade will do.
Common mistakes
Reading the bands from the wrong end.
Start from the end whose bands sit closest to the lead. The tolerance band — usually gold or silver — is spaced slightly apart and belongs last. Reading brown-black-red backwards gives 2 kΩ instead of 1 kΩ.
Treating a gold multiplier band as tolerance.
In the multiplier position gold means ×0.1 and silver ×0.01. A 4-band resistor ending gold-gold is 0.1 × the digits at 5 %, not a 5 % part read some other way.
Counting a 5-band resistor as 4-band.
A 5-band part has three digit bands. Reading only two turns 4.99 kΩ into 49 × 10 = 490 Ω — off by an order of magnitude and easy to miss on a board.
Confusing an inductor for a resistor.
Small inductors use a near-identical band scheme but the unit is microhenries. Check the body shape and the silkscreen designator (R vs L) before decoding.
Ignoring tolerance when a value looks odd.
E24 and E96 series values are not round numbers. 4.7 kΩ, 5.6 kΩ and 4.99 kΩ are all standard; a decode that lands on 5.0 kΩ usually means a band was misread.
Frequently asked questions
How do I read a 4-band resistor?
The first two bands are digits, the third is the multiplier and the fourth is tolerance. Brown-black-red-gold is 1, 0, times 100, so 1000 ohms at 5 percent tolerance.
What is the difference between 4-band and 5-band resistors?
A 5-band resistor uses three digit bands instead of two, then multiplier and tolerance. The extra digit allows values such as 4.99 kilohm, which is why precision resistors use five bands.
Which end of a resistor do I start reading from?
Start from the end where the bands are closest to the lead. The tolerance band is usually gold or silver, sits slightly apart from the rest, and belongs at the far end.
What do gold and silver bands mean?
As a tolerance band, gold is 5 percent and silver is 10 percent. As a multiplier band they mean divide by 10 and divide by 100, which is how sub-ohm values such as 0.22 ohm are marked.
How do I decode SMD resistor markings?
A 3-digit code such as 472 means 47 followed by 2 zeros, so 4.7 kilohm. A 4-digit code such as 4701 means 470 followed by 1 zero, again 4.7 kilohm. An R marks the decimal point, so 4R7 is 4.7 ohm.
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