FormatFlow

No tool matches “”

Try a format (“webp”, “mp3”) or a verb (“merge”, “compress”).

PDF toolsImage toolsVideo toolsAll tools

Loading index

↵to open

Physics Tools · Updated October 21, 2026 · Reviewed by FormatFlow Editorial

Resistor Color Code Calculator

You can decode a 4-band or 5-band resistor from its colors, see the resistance in ohms, kilohms or megohms, and get the tolerance range plus a color reference table.

Runs in your browserFree · No sign-up · No watermark
Bands → resistanceRuns in your browser
Loading the tool…

Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Works with
Bands → resistance
Processing
In your browser
Price
Free, no account
Updated
October 21, 2026
All Physics Tools

About Resistor Color Code Calculator

A resistor's value is printed in colored bands rather than digits: two or three significant digits, a multiplier and a tolerance. Decoding them is easy until the third band mixes with the multiplier on a 5-band part, or the tolerance colors are mistaken for digits. This calculator shows a real swatch for each selected band so the physical part and the decoded value stay aligned.

Choose 4-band or 5-band mode, set each band color, and read the nominal resistance with its minimum and maximum values. Invalid combinations such as a black first band are explained instead of returning a wrong number, and the color reference table covers digits, multipliers and tolerances in one place.

What this tool does

The details that matter when you use Resistor Color Code Calculator for real work.

  • 4-band and 5-band modes

    Switch between the common four-band layout and the precision five-band layout with three significant digits.

  • Real color swatches

    Each band picker shows the actual resistor color, so the on-screen selection matches the physical component.

  • Resistance with units

    The result scales automatically between ohms, kilohms, megohms and gigohms.

  • Tolerance range

    Brown ±1%, red ±2%, gold ±5% and silver ±10%, with the minimum and maximum resistance shown.

  • Invalid combinations rejected

    A black first band or a non-tolerance color in the last position is reported instead of decoded.

  • Color reference table

    Every color's digit, multiplier and tolerance value is listed for quick manual checking.

How to use Resistor Color Code Calculator

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Choose the resistor type

    Select 4-band for the common layout or 5-band for a precision resistor with three significant digits.

  2. 02

    Set each band color

    Use the color pickers, reading the physical resistor from the end opposite the tolerance band.

  3. 03

    Read the resistance

    The headline value is scaled automatically to ohms, kilohms, megohms or gigohms.

  4. 04

    Check the tolerance range

    The summary cards show the tolerance percentage and the minimum and maximum resistance it allows.

  5. 05

    Use the reference table

    Compare an unclear band against the color chart, then press Reset to decode another resistor.

How this tool works

Works with
Bands → resistance
Processing
Client-side, in your browser. Nothing is uploaded.
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Covers 4-band and 5-band resistors only; 6-band temperature-coefficient bands are not decoded.
  • Uses the standard digit, multiplier and tolerance colors; uncommon reliability or temperature bands are not modelled.
  • Faded, dirty or badly lit bands can be misread, so confirm critical values with a meter.

Privacy and file handling

Band selections are decoded in your browser with plain JavaScript. Nothing is uploaded, stored or logged, and no network request is made while you use the calculator.

Read the full privacy policy

Resistor Color Code Calculator FAQ

Short, direct answers to the questions people ask before using this tool.
How do I read a 4-band resistor?
Read from the end opposite the tolerance band: the first two bands are significant digits, the third is the multiplier and the fourth is the tolerance. Brown, red, red and gold decodes as (1 × 10 + 2) × 100 = 1,200 Ω, or 1.2 kΩ, with ±5% tolerance.
How is a 5-band resistor different from a 4-band one?
A 5-band resistor has three significant digits, a multiplier and a tolerance, so it can express precise values such as 10.2 kΩ. The first three bands are digits, the fourth is the multiplier and the fifth is the tolerance; the last band is still read last.
Which end of a resistor should I start reading from?
Start at the end furthest from the tolerance band, which is usually spaced slightly apart and is often gold or silver. If the layout is ambiguous, decode both directions and compare with the expected value from the circuit or a multimeter.
What do gold and silver mean as multiplier bands?
Gold means ×0.1 and silver means ×0.01. They can appear as multipliers or tolerances but never as significant digits, so a resistor with a gold third band is a fraction of an ohm, not a whole-number value.
Why can't the first band be black?
Black represents the digit 0, and a value cannot start with a leading zero, so a black first band does not describe a valid resistor code. The calculator reports this combination as an error rather than silently ignoring the first band.
What tolerance do the color bands represent?
Brown is ±1%, red is ±2%, gold is ±5% and silver is ±10%. The range below the result applies that percentage to the nominal value, so a 1.2 kΩ ±5% resistor can measure between 1.14 kΩ and 1.26 kΩ.
How accurate is reading a resistor by its colors?
The color code gives the nominal value and tolerance, which is all the manufacturer guarantees. Colors fade, lighting changes how brown and red look, and the tolerance range can be wide, so verify any critical value with a multimeter before relying on it.
Where is the temperature coefficient band on a resistor?
Some precision resistors add a sixth band for the temperature coefficient, usually in parts per million per degree Celsius. This calculator decodes 4-band and 5-band resistors only; for a 6-band part, decode the first five bands and look the sixth up separately.

Background reading

Format guides that explain the trade-offs behind Resistor Color Code Calculator.