Resistor Color Code Calculator — Decode Any 4-Band Resistor
Found a resistor in the parts bin and don't know its value? Read its coloured bands left to right — the first two are digits, the third is the multiplier, and the last is tolerance. Enter the colours below, or enter a resistance and get the colours to look for.
Resistor Color Code (4-Band)
Colors → Ohms
100 Ω ±5%
Ohms → Colors
Band 1: Red
Band 2: Red
Multiplier: Brown
Tolerance: Gold (±5%)
The Formula: How to Read the Bands
Decoding a 4-band resistor is simple once you know the formula:
Value = (First Digit × 10 + Second Digit) × Multiplier
The last band isn't a digit, it's the tolerance — how far the real, physical resistance value can vary from the printed one.
Worked Examples
Example 1: Brown, Black, Red, Gold
Value: (1 × 10 + 0) × 100
Result: 1,000 Ω = 1kΩ, ±5%
Example 2: Red, Red, Brown, Gold
Value: (2 × 10 + 2) × 10
Result: 220 Ω, ±5%
Example 3: Yellow, Violet, Orange, Gold
Value: (4 × 10 + 7) × 1,000
Result: 47,000 Ω = 47kΩ, ±5%
Reverse Lookup: Finding bands for 330 Ω
If you need a 330 Ω resistor, look for Orange, Orange, Brown, Gold.
Calculation: (3 × 10 + 3) × 10 = 330 Ω
Common Mistakes (Don't Get Fooled!)
Reading it backwards: Start at the end opposite the gold/silver tolerance band. There is usually a slightly bigger gap before the tolerance band.
Mixing up the multiplier and a digit: The third band multiplies the value, it doesn't just add another digit.
Confusing similar colours: Brown, black, and red can look frustratingly similar under bad workbench lighting. When in doubt, verify with a multimeter!
Assuming 4-band rules for a 5-band resistor: On a 5-band resistor, the third band is a third digit, not the multiplier. The multiplier shifts to the fourth band.
Forgetting tolerance: A "1kΩ ±5%" resistor can actually measure anywhere between 950 Ω and 1,050 Ω in the real world.
Next Steps
Got your resistor value figured out? Here's where to use it next: