Resistor Color Code Calculator
Reads a standard 4-band resistor exactly the way an engineer would by eye — two significant digits, a multiplier, and a tolerance — without needing to memorise the colour-to-number mapping every time.
Inputs
Result
1 kΩ
Tolerance Gold ±5%
How the resistor color code calculator works
Bands 1 and 2 give two significant digits (0-9, colour-coded black through white).
The multiplier band scales that two-digit number by a power of 10 matching its own colour position.
The tolerance band (often gold or silver, set apart from the value bands) states how far the actual resistance may vary from the marked value.
Worked example: Brown, Black, Red, Gold
- Brown = 1, Black = 0 → digits '10'.
- Red multiplier = ×100.
- 10 × 100 = 1,000 Ω = 1 kΩ, with Gold indicating ±5% tolerance.
Common mistakes to avoid
Reading the bands from the wrong end
The tolerance band (commonly gold or silver, and often spaced slightly apart from the others) marks the end of the sequence — reading right-to-left instead of left-to-right gives a completely different, wrong value.
Confusing a 4-band and 5-band resistor
5-band resistors use three digit bands for extra precision instead of two — applying this 4-band tool's logic to a 5-band resistor's colours will misread the value.
Frequently asked questions
How do I know which end to start reading from on a physical resistor?
The tolerance band is usually gold or silver and sits noticeably apart from the tightly-grouped value bands — start reading from the opposite end.
What does the tolerance percentage actually mean in practice?
A 1 kΩ resistor with ±5% tolerance could measure anywhere from 950 Ω to 1,050 Ω and still be within spec — this matters for precision circuits where an exact value is assumed.
Why do component values often look like unusual numbers, like 4.7 kΩ instead of 5 kΩ?
Resistors are manufactured in standardised value series (like E12 or E24) spaced to cover a decade with even percentage steps, not round numbers — 4.7 is one of those standard values.
Can this tool decode a 5-band or 6-band resistor?
No, it's specifically built for the common 4-band case — 5 and 6-band resistors use an additional digit or a temperature coefficient band this tool doesn't account for.
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