Resistor Color Code Calculator
Read the bands without squinting.
Resistor Color Code Calculator
Decode a four-band resistor from its colours, with the tolerance range shown in ohms.
Four-band resistors read digit, digit, multiplier, tolerance. A fifth band, when present, is a temperature coefficient and is not read here.
1.00 kΩ
±5% tolerance
- Exact value
- 1,000 Ω
- Minimum
- 950 Ω
- Maximum
- 1.05 kΩ
- Bands
- Brown · Black · Red · Gold
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What This Calculator Does
The Resistor Color Code Calculator turns four colour bands into a resistance value and a tolerance range. Pick the colours from the dropdowns and it shows the exact value, the minimum and maximum within tolerance, and a visual band preview.
How It Works
The first two bands are digits. The third is a multiplier — a power of ten, with gold and silver standing for 0.1 and 0.01. The fourth band is tolerance as a percentage. The resistance is the two-digit number times the multiplier, and the tolerance spread is that value times the percentage.
Example
Brown, black, red, gold reads as 1, 0, ×100, ±5%. That is 10 × 100 = 1,000 Ω, or 1 kΩ, with a range of 950 Ω to 1,050 Ω. Brown, black, brown, gold would be 100 Ω instead.
Formula
R = (digit₁ × 10 + digit₂) × multiplierRmin = R × (1 − tol); Rmax = R × (1 + tol)Gold = ×0.1, silver = ×0.01These two appear only in the multiplier position, never as digits.
Reading the Results
Resistance
The nominal value at 20 °C. A resistor’s actual value drifts with temperature, which is specified separately as a temperature coefficient.
Tolerance range
The window the manufacturer guarantees. A 1 kΩ ±5% part is in specification anywhere from 950 Ω to 1,050 Ω, which is often fine for a divider and not fine for a precision reference.
Sources and References
IEC 60062 — Marking codes for resistors and capacitors
Colour code for fixed resistors
The international standard that defines band order, digit values, multipliers, and tolerance colours.
IEC 60063 — Preferred number series
E6, E12, E24, E96 value series
Explains why 1 kΩ and 4.7 kΩ exist but 5 kΩ does not: resistors come in preferred-number steps.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
How do I know which end to start from?
Start from the end with the bands grouped closest together. The tolerance band is usually separated slightly from the other three, and gold or silver only ever appears as a multiplier or tolerance, never as a digit.
What does the fifth band mean?
On a five-band resistor, the first three bands are digits and the fourth is the multiplier; the fifth is tolerance. A sixth band is a temperature coefficient. This calculator reads the four-band layout.
Why is there no green or blue multiplier tolerance?
Green and blue do have tolerance meanings (0.5% and 0.25%) and appear in the tolerance position on precision parts. The dropdown shows every colour that has a defined tolerance value.
Can I read a resistor while it is in circuit?
Not reliably. Parallel paths change the measured value, and your meter’s test voltage may turn on semiconductor junctions. Desolder one leg, or isolate the part, before measuring.