How to use the Resistor Colour Code Calculator
- 1. Pick the band countChoose 4, 5 or 6 bands, or switch to value → colours.
- 2. Select each colourStart from the end away from the gold or silver tolerance band.
- 3. Read the valueSee ohms, tolerance range, temperature coefficient and a drawing of the bands.
How the resistor colour code works
Each colour stands for a digit: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. On a 4-band resistor the first two bands are digits, the third is the multiplier (a power of ten) and the fourth is the tolerance. A 5-band resistor has three digit bands, and a 6-band resistor adds a sixth band for the temperature coefficient in ppm/K.
Worked example: yellow, violet, red, gold. Digits 4 and 7 give 47. Red is ×100, so R = 47 × 100 = 4,700 Ω = 4.7 kΩ. Gold means ±5%, so the real value can be anywhere from 4.465 kΩ to 4.935 kΩ. Gold as a multiplier means ×0.1 and silver ×0.01, used for values below 10 Ω.
Typical lab and exam questions
- Find the value of a resistor coded brown, black, orange, gold (10 kΩ ±5%).
- Write the colour code for 220 Ω on a 4-band resistor (red, red, brown).
- A 5-band resistor reads orange, orange, black, brown, brown. What is its value? (330 × 10 = 3.3 kΩ ±1%)
- Find the maximum and minimum values allowed by the tolerance.
Most 5% resistors come in the E24 series (1.0, 1.1, 1.2, 1.3, 1.5 ... 9.1 times a power of ten). The value → colours mode tells you the nearest E24 value when the number you type is not standard.
Frequently asked questions
Which end do I start reading from?
Start from the end opposite the tolerance band. The tolerance band (often gold or silver) is usually set a little apart from the others.
What does a gold or silver third band mean?
As a multiplier, gold is ×0.1 and silver is ×0.01. They are used for low values such as 4.7 Ω (yellow, violet, gold) or 0.47 Ω.
What is the 6th band?
It is the temperature coefficient, in parts per million per kelvin. Brown is 100 ppm/K, which means the value changes by 0.01% for each 1 °C change.
Is this tool free?
Yes. You enter your name and WhatsApp number once to see your result, and all other Uncodemy tools then open without the form.