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Select the four band colors on your resistor and get its exact resistance, tolerance, and value range.
Example
A resistor with bands Brown, Black, Red, Gold decodes as (1, 0) x 100 = 1,000 Ω (1 kΩ) at ±5% tolerance, giving a range of 950 Ω to 1,050 Ω.
How it works
For a 4-band resistor, resistance = (10 x digit1 + digit2) x multiplier, where each color maps to a number (Black=0 to White=9) and the multiplier band is a power of ten. The tolerance band gives the percentage spread, so the range is value x (1 +/- tolerance/100).
Good to know
This Resistor Color Code Calculator turns the four painted bands on a through-hole resistor into a numeric value, so you don't have to memorize the color-to-digit chart or do the power-of-ten math in your head. You pick a color for each band from the dropdowns and it instantly shows the resistance in ohms (auto-scaled to kΩ, MΩ, or GΩ), the tolerance percentage, and the lowest and highest values the part is allowed to actually measure. It's aimed at electronics hobbyists, students, repair technicians, and anyone sorting an unlabeled parts bin.
Reach for it when you've pulled a resistor off a board or out of a drawer and need to confirm its rating before designing a circuit, replacing a component, or checking a reading against a multimeter. The two-digit-plus-multiplier layout it uses is the standard 4-band scheme, where the first two bands are significant figures, the third is the multiplier, and the fourth is tolerance.
To interpret the output, treat the main Resistance number as the nominal (labeled) value and the Minimum/Maximum as the guaranteed window. A 1 kΩ resistor at ±5% is in-spec anywhere from 950 Ω to 1,050 Ω, so a multimeter reading inside that band means the part is fine even if it isn't exactly 1,000 Ω. Tighter tolerances (±1% brown, ±0.5% green) narrow that window considerably.
One practical caveat: getting the band order right matters more than anything else. The tolerance band sits slightly apart, usually gold or silver, so orient the resistor with that band on your right and read inward from the left. If your part has 5 or 6 bands, this 4-band tool won't map it directly, because a third significant-figure band shifts everything over.
Frequently asked questions
How do I know which end is the first band?
The first three bands are usually grouped close together at one end, while the tolerance band (commonly gold or silver) sits slightly apart at the other end. Read from the grouped end inward.
What does the multiplier band do?
The third band multiplies the two-digit number from the first two bands by a power of ten. For example a Red multiplier means x100, while Gold means x0.1 for small sub-ohm values.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser. Your inputs never leave your device, and it works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
What is the color order for a 1k ohm resistor?
A standard 1 k� resistor at 5% tolerance is brown, black, red, gold: brown=1, black=0, red multiplier=x100, giving (10) x 100 = 1,000 ohms, with gold meaning plus or minus 5%.
How do you read a 4-band resistor?
Read from the end where the bands are grouped together. The first two bands are digits, the third is the multiplier (a power of ten), and the fourth, set slightly apart, is the tolerance.
What is the difference between a 4-band and 5-band resistor?
A 4-band resistor uses two significant-figure bands plus a multiplier and tolerance, while a 5-band resistor adds a third significant-figure band for higher precision. A 5-band code cannot be entered directly into a 4-band calculator.
What does a gold or silver band mean on a resistor?
As the tolerance band, gold means plus or minus 5% and silver means plus or minus 10%. As the multiplier band, gold means multiply by 0.1 and silver means multiply by 0.01, used for sub-ohm values.
How accurate is a resistor with 5% tolerance?
A 5% resistor is guaranteed to fall within 5% above or below its nominal value. For a 1,000 ohm part that means any actual value between 950 and 1,050 ohms is considered in-spec.
Can I just measure a resistor with a multimeter instead of reading the bands?
Yes, a multimeter set to ohms reads the actual resistance directly, which is helpful when bands are faded or ambiguous. The color code tells you the labeled value and tolerance, while the meter shows the real measured value.
Why does my resistor read a different value than the color code?
Some difference is normal because resistors are rated within a tolerance, so the measured value can legitimately differ from nominal. A reading outside the stated min/max range, or affected by in-circuit measurement, may indicate a damaged part or a misread band.
What is the resistor color code mnemonic?
A common mnemonic for black, brown, red, orange, yellow, green, blue, violet, grey, white (0 through 9) is sentences like 'Big Boys Race Our Young Girls But Violet Generally Wins.' Each word's first letter matches a color in order.
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