Resistor Color Code Calculator

Last updated: Jul 22, 2026 | Reviewed by Calkulator Team | 2 min read

Science

Read resistor colour bands to find resistance and tolerance

A resistor with Brown-Black-Red-Gold bands is 1,000Ω (1KΩ) ±5%. Select 4 or 5 band colours to decode any resistor value instantly — no more squinting at tiny components with a magnifying glass.

The tolerance band (gold=5%, silver=10%) is always the last band and is slightly spaced from the others.

Number of Bands

Resistance Value

Resistance

—

Tolerance —

Color Code Reference

Color

Digit

Multiplier

Black

×1

Brown

×10

Red

×100

Orange

×1k

Yellow

×10k

Green

×100k

Blue

×1M

Violet

×10M

Grey

—

White

—

Gold

—

×0.1

Silver

—

×0.01

Live Result Illustration

Visual summary — updates instantly as you enter values above

LIVE

Real-Life Guide to Using the Resistor Calculator

Color code to resistance value. Use the examples and checks below to turn the number into a practical decision.

When this calculator is useful

Handy when you have a physical resistor with colored bands and no multimeter on hand, and need to quickly determine its resistance value and tolerance.

For most people, the best way to use the Resistor Calculator is to try the real case first, then change one input at a time. That makes the trade-off visible. For example, with a loan calculator you can change tenure while keeping the same rate; with an investment calculator you can change return assumption while keeping the same monthly contribution; with a health, education or measurement calculator you can check how much one input changes the final category.

The result should answer a practical question: Can I afford this? How much should I save? Is this score enough? Is this measurement within range? What is the safer or cheaper option? If the output does not answer the decision clearly, adjust the inputs until the scenario matches your real situation.

Real-Life Example

Decoding a common LED resistor: A maker building an LED circuit needs to confirm the value of a resistor pulled from a parts bin.

1Bands read red-red-brown-gold: red=2, red=2, brown=×10, gold=±5%, giving 22 × 10 = 220 Ω ± 5% (a range of 209–231 Ω).

2Now change one input, such as rate, time, quantity, unit or score, and compare the new result with the first one.

Because of the 5% tolerance, a multimeter reading of 215 Ω on this resistor is completely normal and not a sign of a faulty part.

Practical Advice

Use the Resistor Calculator as a planning tool, not just a number generator. Write down the inputs you used, because the final answer is meaningful only when you remember the assumptions behind it.

If the decision affects money, health, tax, safety, academics or legal compliance, keep a second check ready. That second check may be a bank quote, payslip, official rule, prescription, site measurement, mark sheet or invoice.

Common Mistakes

Reading the bands starting from the tolerance band (usually gold or silver) instead of ending there — the tolerance band should always be read last.
Applying a 4-band decoding scheme to a 5-band resistor, which has an extra significant-digit band and shifts every subsequent color one position over.
Mistaking the gold or silver multiplier/tolerance band for a colored significant-digit band, especially on resistors with unusual color combinations.
Skipping the temperature coefficient band present on precision 6-band resistors, which does not affect resistance value but does affect stability over temperature.
Confusing black (0) with brown (1) under poor lighting — always double-check by reading the whole sequence rather than a single band in isolation.

How to Interpret Results

The output gives a nominal resistance plus a tolerance range — for example a resistor rated 220 Ω ± 5% can legitimately measure anywhere between 209 Ω and 231 Ω on a multimeter.

A good interpretation looks at both the main result and the supporting values. If a page shows totals, ratios, categories, schedules or warnings, read those together instead of focusing only on the biggest number.

Resistor Calculator FAQs

Useful answers for interpreting the output, avoiding mistakes and using the result responsibly.

How does the resistor color code work?

Each color represents a digit or multiplier: black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, grey=8, white=9. On a 4-band resistor the first two bands are significant digits, the third is a multiplier, and the fourth is tolerance.

What is the difference between 4-band and 5-band resistors?

A 5-band resistor uses three significant-digit bands instead of two, giving finer precision, followed by a multiplier and tolerance band — common on resistors with 1% tolerance or tighter.

What does the tolerance band actually tell me?

It defines how far the real resistance can deviate from the nominal value — gold means ±5%, silver means ±10%, and no band at all means ±20%.

Which end of the resistor do I start reading from?

Start from the end farthest from the tolerance band, since gold and silver are never used as a first significant digit — that positioning is what tells you which direction to read.

I have two colors that look similar under my lighting — how do I avoid misreading them?

Compare against a printed color chart in good lighting, and cross-check your reading by verifying it against a multimeter measurement or the component's expected circuit role.

How does this relate to the Ohm's law calculator?

Once you decode the resistance value here, you can plug it directly into the Ohm's law calculator alongside a known voltage to find the expected current through that resistor.

What if a resistor has no visible tolerance band?

A resistor with only three bands and no fourth band is assumed to have a default tolerance of ±20%, which is common on older or very inexpensive components.

Should I still verify with a multimeter?

Yes — color codes can fade, be misprinted, or be misread, so for anything safety-critical or precision-dependent, confirm the decoded value with an actual multimeter measurement.

Frequently Asked Questions

How do I read resistor colour codes?

For 4-band resistors: the first two bands are significant digits, the third is the multiplier (zeros), and the fourth is tolerance. Red-Red-Brown-Gold = 2, 2, ×10, ±5% = 220 Ω ±5%. A 5-band resistor adds a third significant digit. The mnemonic "BB ROY of Great Britain has a Very Good Wife" gives the colour order (Black through White = 0–9).

What is the difference between series and parallel resistors?

Series: R_total = R1 + R2 + ... (resistances add). Parallel: 1/R_total = 1/R1 + 1/R2 + ... (total resistance is less than the smallest individual value). For two resistors in parallel: R_total = (R1 × R2) ÷ (R1 + R2). Use series to increase total resistance; use parallel to decrease it and distribute current.

What wattage rating should I choose for a resistor?

Choose a resistor with a power rating at least 2× the actual power dissipated. Power = V² ÷ R or P = I² × R. A 1 kΩ resistor with 5V across it dissipates 5² ÷ 1000 = 0.025W. A standard ¼W (0.25W) resistor is fine. Using a higher wattage rating increases reliability and prevents overheating during extended operation.