How do you read a 4-band resistor?

The first two bands are digits, the third is a multiplier as a power of ten, and the fourth is the tolerance. Multiply the two-digit number by the multiplier to get the resistance in ohms.

What do the colours mean?

Black is 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8 and white 9. Gold and silver are used as fractional multipliers and as tolerance bands.

Tolerance is how far the real resistance may differ from the marked value. A gold band means plus or minus 5 percent, silver 10 percent, and brown 1 percent.

Resistor Color Code Calculator

This resistor colour code calculator reads the value of a standard four-band resistor from its coloured stripes, giving you the resistance in ohms and the tolerance. The colour band system is how the value of a small resistor is printed, since the components are far too tiny to label with numbers, and being able to read it is a basic skill for anyone working with electronics. On a four-band resistor the first two bands are digits, the third band is a multiplier that tells you the power of ten to multiply by, and the fourth band is the tolerance, how far the real value may stray from the marked one. You select the colour of each band, and the calculator combines them: it forms a two-digit number from the first two bands, multiplies by the third, and reports the result in ohms, kilo-ohms or mega-ohms as appropriate, along with the tolerance percentage. The colour to number mapping is the standard one, where black is 0 through to white at 9, with gold and silver serving as fractional multipliers and as the common 5 and 10 percent tolerance bands. This saves squinting at a chart every time and helps you confirm a resistor before soldering it in. Choose the four band colours to see the resistance and tolerance straight away.

Band 1 (digit)

Band 2 (digit)

Band 3 (multiplier)

Band 4 (tolerance)

10 kΩ

tolerance ±5%

How it works

The calculator turns the first two band colours into digits and joins them into a two-digit number, multiplies by the third band's multiplier, and formats the result in ohms, kilo-ohms or mega-ohms. The fourth band sets the tolerance, the allowed percentage variation from the marked value.

Worked example

Brown, black, orange, gold reads as 1 and 0 making 10, times the orange multiplier of 1000, giving 10,000 ohms, or 10 kilo-ohms, with a gold tolerance of plus or minus 5 percent.

Related calculators

Series and Parallel Resistance Calculator: combine resistors.
Ohm's Law Calculator: V equals I R.
Electrical Power Calculator: P equals V I.
Watts to Amps Calculator: current from power.

If you've found a bug, or would like to contact us, or learn more about James Graham and Calculate.co.nz.

Calculate.co.nz is partnered with Interest.co.nz for New Zealand's highest quality calculators and financial analysis.

All calculators and tools are provided for educational and indicative purposes only and do not constitute financial advice.

Calculate.co.nz is proudly part of the Realtor.co.nz group, New Zealand's leading property transaction literacy platform, helping Kiwis understand the home buying and selling process from start to finish. Whether you're a first home buyer navigating your first property purchase, an investor evaluating your next acquisition, or a homeowner planning to sell, Realtor.co.nz provides clear, independent, and trustworthy guidance on every step of the New Zealand property transaction journey.

Calculate.co.nz is also partnered with Health Based Building and Premium Homes to promote informed choices that lead to better long-term outcomes for Kiwi households.

Calculate.co.nz is hosted in Auckland via SiteHost new Zealand.

All content on this website, including calculators, tools, source code, and design, is protected under the Copyright Act 1994 (New Zealand). No part of this site may be reproduced, copied, distributed, stored, or used in any form without prior written permission from the owner.