The Resistor Color Code Calculator reads the coloured bands on any standard 4-band through-hole resistor and converts them into a resistance value in ohms, kilohms, or megohms. Select each band colour from the dropdown — first digit, second digit, multiplier, and tolerance — and see the decoded value with its tolerance range. Includes the full colour code chart and BB ROY mnemonic for quick reference.
function rcccCalc(){let b1=parseInt(document.getElementById(‘rccc-b1’).value);
let b2=parseInt(document.getElementById(‘rccc-b2’).value);
let mul=parseFloat(document.getElementById(‘rccc-b3’).value);
let tol=parseInt(document.getElementById(‘rccc-b4′).value);
let val=(b1*10+b2)*mul;
let display=”;
if(val>=1e6)display=(val/1e6)+’MΩ’;
else if(val>=1e3)display=(val/1e3)+’kΩ’;
else display=val+’Ω’;
let min=val*(1-tol/100),max=val*(1+tol/100);
let el=document.getElementById(‘rccc-results’);
el.innerHTML=’
RESISTANCE
‘+display+’
‘
+’
TOLERANCE
±’+tol+’%
‘
+’
RANGE
‘+min.toFixed(1)+’ Ω – ‘+max.toFixed(1)+’ Ω
‘
+’
RAW VALUE
‘+val.toLocaleString()+’ ohms
‘;}
rcccCalc();
How Resistor Color Code Calculator Works
Standard through-hole resistors mark their resistance value with colored bands instead of printed numbers. This calculator decodes a 4-band resistor by combining the two digit bands into a base number, scaling that by the multiplier band, and applying the tolerance band to show the acceptable value range.
Formula: Resistance = (Band 1 digit × 10 + Band 2 digit) × Band 3 multiplier. Tolerance range = Resistance × (1 − Band 4 tolerance ÷ 100) to Resistance × (1 + Band 4 tolerance ÷ 100).
Band 1 — first significant digit, from Brown (1) through White (9)
Band 2 — second significant digit, from Black (0) through White (9)
Band 3 — multiplier band, from Black (×1) up to Blue (×1,000,000), or Gold (×0.1) and Silver (×0.01) for sub-10 ohm values
Band 4 — tolerance band, Gold (±5%), Silver (±10%), Brown (±1%), or Red (±2%)
Example Scenarios
Band 1
Band 2
Multiplier
Tolerance
Resistance
Yellow (4)
Violet (7)
Red (×100)
Gold (±5%)
4.7 kΩ (4,465–4,935 Ω)
Brown (1)
Black (0)
Brown (×10)
Gold (±5%)
100 Ω (95–105 Ω)
Red (2)
Red (2)
Orange (×1K)
Silver (±10%)
22 kΩ (19,800–24,200 Ω)
Green (5)
Blue (6)
Black (×1)
Brown (±1%)
56 Ω (55.44–56.56 Ω)
Orange (3)
Orange (3)
Yellow (×10K)
Gold (±5%)
330 kΩ (313,500–346,500 Ω)
Brown (1)
Black (0)
Gold (×0.1)
Gold (±5%)
1 Ω (0.95–1.05 Ω)
Reading the Bands Before You Use the Resistor Color Code Calculator
A resistor color code calculator can only decode what you feed it, and most wrong values start with a misread band.
Find the tolerance band first. Gold or silver sits at one end, often after a small gap, so read from the opposite end.
Use good light. Red, orange and brown blur together under warm bulbs; daylight or a white LED helps you choose the right colour in the resistor color code calculator.
Count the bands. This resistor color code calculator handles 4-band parts; 5- and 6-band precision resistors use three digit bands and decode differently.
When the value matters, confirm it with a multimeter, measuring out of circuit because parallel parts skew the reading. A result inside the tolerance range from the resistor color code calculator confirms your colours; one far outside it points to a misread band or a heat-damaged part. The electronic color code article on Wikipedia reproduces the IEC 60062 chart if you want to cross-check the resistor color code calculator.
Resistor Color Code Calculator FAQ
How do I read a 4-band resistor?Orient the resistor so the tolerance band (usually gold or silver) is on the right. Read the remaining bands left to right: first digit, second digit, then the multiplier band, which tells you how many zeros to add or what fraction to scale by.What does the multiplier band actually do?It scales the two-digit base number formed by bands 1 and 2. For example, Black means ×1 (no change), Orange means ×1,000, and Gold or Silver mean ×0.1 or ×0.01 for resistances under 10 ohms.What is the tolerance band and why does it matter?The tolerance band tells you how far the resistor’s actual resistance may vary from its labeled value, expressed as a percentage. A 4.7kΩ resistor with a gold (±5%) tolerance band could measure anywhere from about 4,465 to 4,935 ohms and still be within spec.What’s an easy way to remember the resistor color order?A common mnemonic is “BB ROY of Great Britain has a Very Good Wife,” which maps to Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White — the digit values 0 through 9 in order.Does this calculator work for 5-band or 6-band resistors?No, this tool is built specifically for standard 4-band resistors (two digits, one multiplier, one tolerance). 5-band and 6-band resistors add a third digit band for extra precision, and sometimes a temperature coefficient band, which changes how the value is decoded.Why do gold and silver appear as both multiplier and tolerance colors?Gold and silver serve different roles depending on which band position they’re in. In the multiplier position they represent fractional scale factors (×0.1 and ×0.01), while in the tolerance position they indicate the resistor’s precision (±5% and ±10%).
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Related Calculators
Once you know a resistor’s value, the Ohm’s Law calculator can help you work out voltage, current, or power in the same circuit. If you’re converting between the multiplier scales used here and standard powers of ten, the scientific notation converter is handy, and the significant figures calculator can help when rounding measured resistance values for a report. You may also find the 555 Timer Calculator useful.
The resistor colour code calculator decodes the coloured bands on through-hole resistors to reveal resistance and tolerance.
4-Band 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%
Gold
—
×0.1
±5%
Silver
—
×0.01
±10%
Reading Order
Hold resistor with grouped bands left, tolerance (gold/silver) right
Band 1 = first digit, Band 2 = second digit
Band 3 = multiplier, Band 4 = tolerance
Mnemonic: BB ROY of Great Britain has a Very Good Wife
Black Brown Red Orange Yellow Green Blue Violet Grey White = 0 1 2 3 4 5 6 7 8 9
Frequently Asked Questions
Which end of a resistor should I read first?
Read from the end opposite the tolerance band. The gold or silver tolerance band is usually spaced slightly farther from the other bands and should be on the right, while the first color band starts on the left.
What do the gold and silver bands mean?
Gold and silver can represent either a multiplier or a tolerance, depending on their position. As tolerance bands, gold means ±5% and silver means ±10%. As multiplier bands, gold represents ×0.1 and silver represents ×0.01.
How do 5-band resistors differ from 4-band resistors?
A 5-band resistor uses three significant digits instead of two, followed by the multiplier and tolerance bands. This provides greater precision for resistor values.
What if a resistor has no tolerance band?
If there is no separate tolerance band, the resistor typically has a tolerance of ±20%. These resistors are less common in modern electronic circuits.
Can this calculator read SMD resistor codes?
No. Surface-mount (SMD) resistors use printed numeric or alphanumeric codes instead of colored bands. This calculator is designed for standard color-coded resistors only.
Is the resistor color code calculator free?
Yes, this resistor color code calculator is completely free to use, requires no sign-up, and instantly converts resistor color bands into resistance values and tolerances.
