How to Read Resistor Color Codes: 4, 5 and 6-Band Guide

A resistor tells you its value with colored stripes, and once you know the system you can read one in about two seconds. The system trips people up for three reasons: knowing which end to start from, remembering what the multiplier band does, and realizing that a "1 kΩ" resistor is often not 1 kΩ at all.

The Band System

Every color maps to a digit. The same table drives all resistor codes, so it is the only thing worth memorizing:

Color	Digit	Multiplier	Tolerance	Temp. coefficient
Black	0	×1	—	250 ppm/K
Brown	1	×10	±1 %	100 ppm/K
Red	2	×100	±2 %	50 ppm/K
Orange	3	×1 k	—	15 ppm/K
Yellow	4	×10 k	—	25 ppm/K
Green	5	×100 k	±0.5 %	20 ppm/K
Blue	6	×1 M	±0.25 %	10 ppm/K
Violet	7	×10 M	±0.1 %	5 ppm/K
Gray	8	×100 M	±0.05 %	1 ppm/K
White	9	×1 G	—	—
Gold	—	×0.1	±5 %	—
Silver	—	×0.01	±10 %	—

Four Bands: the Classic

Digit, digit, multiplier, tolerance. Brown-black-red-gold reads as 1, 0, ×100, ±5 % — a 1 kΩ resistor with 5 % tolerance. Yellow-violet-orange-gold is 4, 7, ×1 000 = 47 kΩ ±5 %.

Five Bands: Precision Parts

Digit, digit, digit, multiplier, tolerance. The extra digit allows values that four bands cannot express. Brown-black-black-brown-brown is 1, 0, 0, ×10 = 1 kΩ ±1 %. Note that the same 1 kΩ value looks completely different in the two systems — this is the single most common source of misreadings.

Six Bands: Adds Temperature Behavior

Same as five bands, with a final band giving the temperature coefficient in parts per million per kelvin. A 100 ppm/K resistor drifts 0.1 % across a 10 K temperature change — irrelevant in a hobby circuit, significant in a precision reference or a measurement front end.

Which End Do You Start From?

The bands are not symmetrical, and getting the direction wrong turns 47 Ω into 74 Ω or worse. Three reliable cues, in order of dependability:

1. The tolerance band is usually gold or silver. Neither color is ever a leading digit, so if you see gold or silver, that end is the tail. Put it on the right and read from the left.
2. The gap is wider before the tolerance band. Manufacturers group the value bands and leave a slightly larger space before the last one.
3. The tolerance band sits closer to the lead. The value bands cluster toward the middle of the body.

When all the bands are the same width and no gold or silver appears — common on 1 % five-band parts where the tolerance band is brown — the safest move is to measure with a multimeter rather than guess. Reading it backwards is easy: brown-black-black-brown-brown reversed becomes brown-brown-black-black-brown, which is a completely different 110 Ω.

Why Your 1 kΩ Resistor Is Not 1 kΩ

Resistors are manufactured to preferred values called the E-series, defined by IEC 60063. Each series divides a decade into logarithmically spaced steps so that the tolerance bands of adjacent values just touch, without leaving gaps or excessive overlap:

• E6 (±20 %): 10, 15, 22, 33, 47, 68
• E12 (±10 %): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
• E24 (±5 %): adds 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75, 91
• E96 (±1 %): 96 values per decade, three significant digits

This explains the values that look arbitrary until you see the pattern — 4.7 kΩ, 2.2 kΩ, 3.3 kΩ, 6.8 kΩ. It also explains why you cannot buy a 5 kΩ resistor from a standard E12 range but can buy 4.7 kΩ everywhere.

The practical consequence for circuit design: a 5 % resistor marked 1 kΩ is guaranteed only to be somewhere between 950 Ω and 1 050 Ω. If a divider or timing network needs better than that, either buy 1 % parts or measure and select. The color code calculator converts in both directions — bands to value, and a target value to the nearest available E-series part.

Surface-Mount Resistors: Numbers Instead of Colors

SMD parts are too small for stripes and use printed codes instead.

Three-digit code

Two significant digits plus a power-of-ten multiplier. 103 is 10 × 10³ = 10 kΩ. 472 is 47 × 10² = 4.7 kΩ. 100 is 10 × 10⁰ = 10 Ω, not 100 Ω — the classic beginner trap.

Four-digit code

Three significant digits plus multiplier, used for 1 % parts. 1002 is 100 × 10² = 10 kΩ.

R notation

The letter R marks the decimal point for values below 10 Ω. 4R7 is 4.7 Ω, R22 is 0.22 Ω.

EIA-96 code

Two digits plus a letter, used on very small precision parts. The digits index a lookup table of E96 values and the letter is the multiplier: 01A is 100 Ω, 68C is 49.9 kΩ. This one genuinely requires a table — the SMD code decoder handles all four notations.

The Specifications Beyond Resistance

Resistance is only the first number. Three others decide whether a part survives in your circuit:

Power rating

Dissipation is P = I²R, or equivalently V²/R. A 220 Ω resistor dropping 5 V dissipates 114 mW, comfortable for a standard 250 mW part. The same resistor across 12 V dissipates 655 mW and will run hot enough to discolour the board on a 250 mW part. The working rule is to size for no more than half the rated power in continuous operation — derating buys you both reliability and a part that does not cook the components next to it.

Voltage rating

Often forgotten because it rarely matters at low voltages. Standard through-hole resistors are typically rated 200–500 V; small SMD parts can be as low as 50 V. In mains-adjacent circuits, exceeding the rating causes arcing across the body regardless of how comfortable the power dissipation looks.

Temperature coefficient

Carbon film parts run at 200–1 000 ppm/K, metal film at 25–100 ppm/K. In a precision divider feeding an ADC, the difference between those two is the difference between a stable reading and one that wanders as the board warms up.

Series, Parallel and Getting Values You Cannot Buy

Series resistances add: R = R₁ + R₂. Parallel resistances combine as R = (R₁ × R₂) ÷ (R₁ + R₂). Two useful consequences:

• Two equal resistors in parallel give half the value — 2 × 10 kΩ in parallel is a 5 kΩ you cannot otherwise buy in E12.
• Parallel combination also doubles the power handling, which is a legitimate way to dissipate more heat across a larger surface area.
• Tolerances do not simply add. Combining two 5 % parts gives a result whose worst case is still 5 %, but whose typical error is lower because manufacturing spreads partly cancel.

For dividers, what matters is the ratio rather than the absolute values, so two resistors from the same batch tend to track each other better than their individual tolerances suggest. The voltage divider calculator works out the output voltage and the current drawn, which is the figure that decides whether your divider loads the source unacceptably.

Quick Reference

• Gold or silver band on the right, read left to right.
• Four bands: two digits, multiplier, tolerance. Five bands: three digits, multiplier, tolerance.
• Brown tolerance band means 1 %; gold means 5 %; silver means 10 %.
• Odd-looking values like 4.7 kΩ and 3.3 kΩ come from the E-series, not from whim.
• SMD 103 is 10 kΩ; 4R7 is 4.7 Ω.
• Keep continuous dissipation under half the rated power.
• When the bands are ambiguous, measure. A multimeter is faster than a wrong assumption.