Electronics and projects
Ohm's law
Enter any two of voltage, current, resistance and power and get the other two, with the working.
Class 10 to 12, diploma, makers
Electronics and projects
Resistor colour code calculator
Pick the colours you see on a resistor and get its value and tolerance, or type a value and see which colours to look for in the box. Works for 4-band and 5-band resistors.
- Made forClass 6 to 12, diploma, makers
- Shows the workingEvery step, ready for your practical file
- 2 calculators in oneColours to value, Value to colours
Read the colour bands
Hold the resistor so the tolerance band (often gold or silver, set a little apart) is on the right, then pick the colours from left to right.
Resistance1 kΩ±5% tolerance: anywhere from 950 Ω to 1.05 kΩ
BrownBlackRedGold
- In ohms
- 1,000 Ω
- Tolerance
- ±5%±50 Ω
- Standard series
- E12 (and E24)
Working
- Digit bands: Brown = 1, Black = 0, which reads 10.
- Multiplier: Red = ×100.
- 10 ×100 = 1,000 Ω = 1 kΩ.
- Tolerance: Gold = ±5%, and 1,000 × 5% = 50 Ω, so the real value can be 950 Ω to 1.05 kΩ.
- Good to know: 1 kΩ is a standard E12 value, the most common range sold in kits.
- Tip: Measure it with a multimeter on the Ω range before soldering. A reading inside the tolerance range means the bands were read correctly.
Find the bands for a value
Type the resistance you need (4.7k and 4k7 both work) and see the colours to look for in the box of resistors.
Colour bandsYellow, Violet, Brown, Gold470 Ω ±5%
YellowVioletBrownGold
- Value shown
- 470 Ω470 Ω
- Standard series
- E12 (and E24)
- Next E12 above
- 560 Ω
Working
- 470 Ω = 47 ×10.
- Digits 4, 7 are Yellow, Violet.
- ×10 is Brown; the tolerance band is Gold.
- Good to know: 470 Ω is a standard E12 value, the most common range sold in kits.
What it works out
Understanding the resistor colour code
A resistor is too small to print numbers on, so its value is written as coloured bands. The first two bands (three on a 5-band resistor) are digits, the next band is the multiplier, which says how many zeros follow (gold and silver mean ×0.1 and ×0.01), and the last band is the tolerance: how far the real value may be from the printed one.
The calculator reads the code both ways and draws the resistor so you can hold the real part next to the screen. It also tells you whether the value belongs to the standard E12 or E24 series, the ranges resistor kits are sold in, which is a quick way to catch a misread band.
Formula and worked example
Working out the resistor colour code by hand
The calculator uses exactly these formulas. Write them in your notebook and check one answer by hand: it is the surest way to remember them.
The formula
- 4 bands: R = (10 × D1 + D2) × M
- 5 bands: R = (100 × D1 + 10 × D2 + D3) × M
- Real value lies between R × (1 − T ÷ 100) and R × (1 + T ÷ 100)
- D
- digit band: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9
- M
- multiplier band: black ×1, brown ×10, red ×100 … gold ×0.1, silver ×0.01
- T
- tolerance band in %: brown 1, red 2, gold 5, silver 10, no band 20
Worked example
A yellow, violet, brown, gold resistor
- Yellow is 4 and violet is 7, so the digits read 47.
- Brown in the third place is the multiplier ×10: 47 × 10 = 470 Ω.
- Gold is ±5%. 5% of 470 Ω is 23.5 Ω, so a good part measures anywhere from 446.5 Ω to 493.5 Ω.
- If a multimeter shows 468 Ω, the resistor is fine and you read it the right way round.
Answer470 Ω ±5% (446.5 Ω to 493.5 Ω)
Resistor colour code chart
| Colour | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | – |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | – |
| Yellow | 4 | ×10k | – |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | ×100M | – |
| White | 9 | ×1G | – |
| Gold | – | ×0.1 | ±5% |
| Silver | – | ×0.01 | ±10% |
| No band | – | – | ±20% |
In projects and exams
How students use it
Read 4-band and 5-band resistors, or find the colours for any value, on a drawn resistor. Here is where it earns its place in a school year.
Sorting a mixed bag
Kits and repair boxes mix values. Read each resistor before it goes on the breadboard, and confirm doubtful ones with a multimeter.
Physics practicals
Experiments that plot voltage against current use a known resistor. Reading its code first lets you predict the answer before you measure it.
Arduino and robot circuits
Pull-down resistors, LED resistors and sensor dividers each need a particular value; the bands are how you find the right one in the kit.
Answering the viva
Examiners and exhibition judges often ask how you chose a part. Reading its colour code on the spot shows you understand your own circuit.
Check your work
Common mistakes to avoid
These are the slips that cost marks in exams and burn out parts on the bench.
Starting from the wrong end
The tolerance band, often gold or silver, goes on the right and is usually set a little apart. Gold and silver are never the first band.
Treating the multiplier as a digit
On a 4-band resistor the third band is the multiplier, not a third digit: brown, black, red is 1 kΩ, not 102 Ω.
Mixing up similar colours
Brown, red and orange, or blue, violet and grey, look alike under yellow light. Check in daylight, or measure.
Losing the k
4.7 kΩ is 4,700 Ω. Writing 4.7 Ω in a calculation makes the current a thousand times too big.
Questions
Questions about the resistor colour code
Stuck on a project or a sum? Ask the institute on WhatsApp.
Ask on WhatsAppWhat do gold and silver mean on a resistor?
As the last band they are the tolerance: gold is ±5% and silver is ±10%. In the multiplier position, gold means ×0.1 and silver means ×0.01, which is how values below 10 Ω are written.
How do I know which end to start reading from?
Start from the end away from the tolerance band. The tolerance band is often gold or silver, slightly separated from the others, and gold or silver never comes first. If you are still unsure, read it both ways: usually only one way gives a standard value, and a multimeter settles it.
What is the difference between 4-band and 5-band resistors?
A 5-band resistor has three digit bands instead of two, so it can show values such as 4.99 kΩ. They are usually precision metal film resistors, often with a 1% (brown) tolerance band.
What is a resistor with a single black band?
A zero-ohm link: a piece of wire in a resistor body, used as a jumper on circuit boards that are assembled by machines.
Why does my multimeter show a slightly different value?
The tolerance allows it (a ±5% 1 kΩ part can read 950 to 1,050 Ω). Also measure the resistor out of the circuit, and do not hold both leads with your fingers, because your body adds a path in parallel for large values.
Free ebooks
Read more about the resistor colour code
Free PDF ebooks in easy English: download, print and share them.
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