Resistor Color Code Calculator

How to read a resistor colour code

A through-hole resistor carries its value as a set of painted rings. The trick is working out which end to start from, because the code is only meaningful read in one direction.

1. Find the tolerance band

The tolerance band is the last band, and it is usually separated from the others by a slightly wider gap. On cheap parts it is gold (±5%) or silver (±10%), neither of which is ever used as a digit — so if you can see gold or silver at one end, that end is the tail. Hold the resistor with that band on the right and read left to right.

On precision resistors the tolerance band is brown, red, green, blue, violet or grey, which are also valid digit colours. In that case fall back on the gap: the space between the multiplier and tolerance bands is wider than the spaces between the digit bands.

2. Read the digit bands

The first two bands (three on a 5- or 6-band part) are the significant digits, using the sequence black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. The mnemonic most people are taught in the workshop covers the same order; whichever you use, the important thing is that black is zero and white is nine.

3. Apply the multiplier

The next band is a power of ten using the same colour-to-number mapping: brown means ×10, red ×100, orange ×1 k, and so on. Gold and silver extend the range downwards to ×0.1 and ×0.01, which is how you get sub-10 Ω values like 4.7 Ω (yellow, violet, gold).

4. Note the tolerance — and the sixth band if present

Tolerance tells you how far the real part may sit from its nominal value: ±5% on a 10 kΩ resistor means anything from 9.5 kΩ to 10.5 kΩ is in spec. A sixth band, when fitted, is the temperature coefficient in parts per million per degree Celsius — brown is 100 ppm/°C, red 50, and so on down to violet at 5 ppm/°C for the most stable parts.

Worked examples

Yellow · Violet · Red · Gold

Digits 4 and 7 give 47. Red is ×100. So 47 × 100 = 4,700 Ω = 4.7 kΩ, gold tolerance ±5%, meaning the real part is somewhere between 4.465 kΩ and 4.935 kΩ.

Brown · Black · Black · Red · Brown (5-band)

Digits 1, 0 and 0 give 100. Red is ×100. So 100 × 100 = 10,000 Ω = 10 kΩ, brown tolerance ±1%. Note how a 5-band part expresses the same 10 kΩ differently from the 4-band brown-black-orange — the extra significant figure shifts the multiplier down by one decade.

Green · Blue · Black · Gold · Brown (5-band)

Digits 5, 6 and 0 give 560. Gold is ×0.1. So 560 × 0.1 = 56 Ω, ±1%. This is the pattern that catches people out — a gold band in the fourth position of a five-band resistor is a multiplier, not the tolerance.

4-band, 5-band and 6-band resistors

The band count tells you how precise the part claims to be:

• 4 bands — two significant figures, ±5% or ±10%. General-purpose carbon film. Values come from the E12 or E24 series.
• 5 bands — three significant figures, typically ±1%. Metal film. Values come from E48 or E96, which is why you see odd-looking numbers like 4.99 kΩ and 2.21 kΩ.
• 6 bands — three significant figures plus a temperature coefficient. Used where drift over temperature matters: reference dividers, instrumentation amplifier gain setting, current-sense networks.

Common mistakes

• Reading the resistor backwards. Brown-black-red is 1 kΩ; red-black-brown is 200 Ω. Always locate the tolerance band first.
• Confusing brown and red under warm light. Incandescent bench lamps shift both towards orange. Check under daylight or with a phone torch, and confirm with a multimeter if the difference matters.
• Assuming a 5-band part is 4-band. If the value you get looks absurd — 4.7 MΩ where you expected a few hundred ohms — recount the bands.
• Trusting the code over the meter on a used part. A resistor that has been cooked shifts high and its bands do not change colour. Measure anything you have desoldered from a failed board.
• Ignoring the body colour. Some wirewound and fusible resistors use a white or grey ceramic body and the code does not apply at all; those parts are usually printed rather than banded.

What tolerance actually costs you

Tolerance stacks. Two ±5% resistors in a divider can be off by roughly ±10% in the worst case, which is why precision analogue work uses ±1% or better parts even where the nominal value is not critical. If a ratio matters more than an absolute value — as in a voltage divider or an amplifier gain network — consider a matched pair or a resistor array, where the parts track each other far more closely than their individual tolerances suggest.

Frequently asked questions

How do I know which end of a resistor to start reading from?

Look for the band that sits slightly apart from the rest — that is the tolerance band, and it goes on the right. Gold and silver are never digit colours, so if you see either at one end you have found the tail. On precision resistors where every band is a digit colour, use the wider gap before the last band.

What does a 5-band resistor mean compared to a 4-band one?

A 5-band resistor gives three significant figures instead of two, so it can express values like 4.99 kΩ that a 4-band part cannot. It is almost always a ±1% metal film part drawn from the E48 or E96 series, whereas 4-band parts are ±5% or ±10% carbon film from E12 or E24.

What is the sixth band for?

The sixth band is the temperature coefficient in parts per million per degree Celsius. Brown is 100 ppm/°C, red 50, orange 15, yellow 25, blue 10 and violet 5. It tells you how much the resistance drifts as the part heats up, which matters in references, current-sense networks and precision dividers.

Why does my multimeter read a different value from the colour code?

Within the tolerance band, that is normal and expected — a ±5% 10 kΩ part is in spec anywhere from 9.5 kΩ to 10.5 kΩ. If the reading is outside tolerance the part has probably been overheated or damaged. Also check you are not measuring it in-circuit, where parallel paths pull the reading low.

Can I use this calculator for SMD resistors?

No — surface-mount resistors are marked with printed numeric codes rather than colour bands. Use the SMD resistor code calculator for 3-digit, 4-digit, R-notation and EIA-96 markings.

Is a value the calculator flags as non-standard wrong?

Not necessarily, but it is worth a second look. Standard resistors come from the E-series, so a mantissa outside E24 or E96 usually means a band has been misread — or that you are holding an unusual precision or military-spec part.