Basics calculator
Resistor colour code
Two digits, then how many zeros: the third band is a zoom, not a digit.
Free. It runs in your browser: nothing to install.
The example, worked out
Given
- I have
- A value
- Resistance
- 4.7 kΩ
- Tolerance
- Gold 5 %
Working
- yellow 4, violet 7, red × 10^2
Results
The formulas
- R = (10 × d1 + d2) × 10^mtwo digits and a multiplier
- black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9the ten colours
The usual traps
- Reading from the wrong end: the tolerance band (gold, silver) sits apart.
- Gold as a multiplier means ×0.1, not a digit.
Questions
How do I read a resistor's colour bands?
R = (10 × d1 + d2) × 10^m: two digits and a multiplier. black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9: the ten colours.
What does it give for typical values?
4.7 kΩ ± 5 %: yellow, violet, red, gold. Value: 4.7 kΩ.
What are the usual mistakes?
Reading from the wrong end: the tolerance band (gold, silver) sits apart. Gold as a multiplier means ×0.1, not a digit.
In the app
Your circuit, drawn live
Change a value: the schematic redraws with your numbers on the parts.
The part you can buy
Results rounded to standard values (E12, E24, E96) and power ratings.
The working, shown
Every step written out. Try it first by hand, then check.
Into your notebook
One click puts the circuit on a sheet of your project.
Open the calculatorOpens in the app on 1 December, with Circuit Notebook 1.0
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