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Resistor Calculator

Electronics & PhysicsResistors and Capacitors
Number of bands
Resistance —
Nominal value in ohms
—
Lowest value within tolerance
—
Highest value within tolerance
—
Significant digits
—

Read the bands from the end opposite the gold or silver band. The first two (or three) colours are digits, the next is a power-of-ten multiplier, and the last is tolerance. Yellow (4), violet (7), red (×100), gold (±5%) gives 47 × 100 = 4,700 Ω, so 4.7 kΩ, acceptable anywhere from 4.465 to 4.935 kΩ.

About this tool

Hobbyists sorting a parts drawer, students on a breadboard and technicians replacing a burnt part all meet the same problem: the value is printed as coloured stripes, not digits. Pick the colour of each band and the calculator gives the nominal resistance with a sensible unit prefix, the exact value in ohms, and the lowest and highest value the part may measure within its tolerance. It handles both the common 4-band code and the 5-band code used on 1% and tighter metal-film parts, and lists the working so you can check each band. It does not decode the sixth temperature-coefficient band or SMD numeric codes such as 472 or 01C; those use different schemes.

How to use it

  1. Choose 4 or 5 bands

    Count the stripes. Five-band parts add a third digit band, which appears when you pick 5 bands.

  2. Set the digit bands

    Start at the end away from the gold or silver stripe and pick each digit colour in order.

  3. Set multiplier and tolerance

    The second-to-last band is the multiplier and the last, often set slightly apart, is the tolerance.

  4. Read the range

    Compare a multimeter reading with the lowest and highest values to judge whether the part is in spec.

Examples

Yellow, violet, red, gold

Number of bands
4 bands
Band 1 (first digit)
Yellow (4)
Band 2 (second digit)
Violet (7)
Multiplier band
Red (×100)
Tolerance band
Gold (±5%)

Result Resistance: 4.7 kΩ ±5%
Nominal value in ohms: 4,700
Lowest value within tolerance: 4.465 kΩ
Highest value within tolerance: 4.935 kΩ
Significant digits: 47

  1. Significant digits: yellow, violet = 47
  2. Multiplier: red = ×10^2
  3. R = 47 × 10^2 = 4.7 kΩ
  4. Tolerance ±5%: 4.465 kΩ to 4.935 kΩ

A common 4.7 kΩ pull-up resistor. Any part measuring between 4.465 and 4.935 kΩ is within its 5% rating.

Brown, black, black, brown, brown

Number of bands
5 bands (precision)
Band 1 (first digit)
Brown (1)
Band 2 (second digit)
Black (0)
Band 3 (third digit)
Black (0)
Multiplier band
Brown (×10)
Tolerance band
Brown (±1%)

Result Resistance: 1 kΩ ±1%
Nominal value in ohms: 1,000
Lowest value within tolerance: 990 Ω
Highest value within tolerance: 1.01 kΩ
Significant digits: 100

  1. Significant digits: brown, black, black = 100
  2. Multiplier: brown = ×10^1
  3. R = 100 × 10^1 = 1 kΩ
  4. Tolerance ±1%: 990 Ω to 1.01 kΩ

A 1% metal-film resistor uses three digit bands, so 100 × 10 gives 1 kΩ, allowed from 990 Ω to 1.01 kΩ.

How it is calculated

R = D × 10^M, range = R × (1 ± T/100)

D
the significant digits read as one number (two bands, or three on 5-band parts)
M
the multiplier exponent: black 0 up to violet 7, gold −1, silver −2
T
tolerance in percent: brown 1, red 2, gold 5, silver 10, none 20

The colours follow IEC 60062, where black to white stand for 0 to 9. The digit bands are joined into one integer and scaled by a power of ten given by the multiplier band, so gold and silver allow values below 10 Ω. The tolerance band sets how far the real part may sit from nominal; the range shown is simply the nominal value scaled down and up by that percentage.

When not to use it

  • Surface-mount resistors are marked with digits such as 103 or EIA-96 codes, not colours.
  • A sixth band gives the temperature coefficient, which this calculator ignores.
  • Heat-discoloured bands can be misread, so measure such parts with a meter instead.

Common mistakes

  • Reading the resistor backwards, starting from the gold or silver tolerance band.
  • Confusing red with orange or brown under warm lighting.
  • Treating the third band of a 5-band part as the multiplier.

Frequently asked questions

Which end of a resistor do I start reading from?

Start from the end where a band sits closest to the lead. The tolerance band, usually gold or silver on 4-band parts, is normally spaced a little apart at the other end. A first band can never be black, because that would be a leading zero; if your reading starts with black, turn the part around.

What do gold and silver mean in the multiplier position?

They divide instead of multiply. Gold is ×0.1 and silver is ×0.01, which is how low values are coded. Green, blue, gold reads 56 × 0.1 = 5.6 Ω.

Why do 5-band resistors exist?

Tighter-tolerance parts, typically 1% and better, come from the E96 and E192 series, whose values need three significant digits, such as 10.2 kΩ. A fifth band carries that third digit.

My meter reads slightly off the nominal value. Is the resistor faulty?

Not if the reading falls inside the tolerance range shown. A 4.7 kΩ ±5% part reading 4.6 kΩ is fine. Measure it out of circuit, since parallel paths on a board make the reading lower than the true value.

What does a resistor with no tolerance band mean?

Three bands only means ±20%, a rating mostly found on older carbon-composition resistors. Modern parts almost always carry a tolerance band.

How can I remember the colour order?

The digits run black, brown, red, orange, yellow, green, blue, violet, grey, white for 0 to 9. Red to violet follows the rainbow, with black and brown before it and grey and white after.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 27). Resistor Calculator. Tools Directory. Retrieved October 27, 2026, from https://tools.milunir.com/electronics-physics/resistors-and-capacitors/resistor-calculator/

MLA

Tools Directory Editorial Team. “Resistor Calculator.” Tools Directory, 27 Oct. 2026, https://tools.milunir.com/electronics-physics/resistors-and-capacitors/resistor-calculator/. Accessed 27 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Resistor Calculator.” Tools Directory. Last modified October 27, 2026. Accessed October 27, 2026. https://tools.milunir.com/electronics-physics/resistors-and-capacitors/resistor-calculator/.

Link<a href="https://tools.milunir.com/electronics-physics/resistors-and-capacitors/resistor-calculator/">Resistor Calculator – Tools Directory</a>