How to read a resistor color code

Short answer

The bands on an axial resistor encode digits, a multiplier and a tolerance. Some components add a third significant digit or a sixth band for the temperature coefficient. To read them correctly, first determine the orientation and then assign a role to each position.

You can follow the process by hand and check each combination with the resistor color code calculator.

Identify how many bands there are

A five-band resistor is not a four-band code with extra data at the end: the third band becomes another digit and the multiplier moves to the fourth position.

Decide which end to read from

The first band is usually closer to one end of the body. The band of tolerance may remain somewhat separated from the group. In four-band codes, gold or silver are clear clues to the end because they do not represent a first figure.

If the spacing and colors allow two reasonable orientations, do not guess. Consult the manufacturer’s documentation and measure the unpowered resistor, ideally with at least one lead disconnected from the circuit.

Digit table

The same colors act as powers of ten when they occupy the position of the multiplier: black is ×1, brown is ×10, red is ×100, orange is ×1,000, and so on. Gold multiplies by 0.1 and silver by 0.01.

Four band example: 1 kΩ ±5%

Read Brown · Black · Red · Gold:

Brown = 1
Black = 0
Red = ×100
Gold = ±5%

10 × 100 = 1,000 Ω = 1 kΩ

The 5% tolerance represents a maximum nominal deviation of 50 Ω:

Minimum = 1,000 × 0.95 = 950 Ω
Maximum = 1,000 × 1.05 = 1,050 Ω

The expected tolerance range is from 950 Ω to 1.05 kΩ.

Five band example: 10 kΩ ±1%

Read Brown · Black · Black · Red · Brown:

Digits: 1, 0, 0 → 100
Red multiplier: ×100
Brown tolerance: ±1%

100 × 100 = 10,000 Ω = 10 kΩ

1% of 10 kΩ is 100 Ω, so the range is 9.9 kΩ to 10.1 kΩ.

If you interpreted the third band as a multiplier, you would shift the positions and you would get a completely different value. Count the bands before converting the colors.

Common tolerances

Additional precision tolerances exist. If the component does not fit the usual scheme, treat its datasheet as the authority.

What does the sixth band indicate?

In the generic six-band scheme, the last one represents the coefficient of temperature or TCR, expressed in parts per million per kelvin (ppm/K). For example:

Brown · Black · Black · Red · Brown · Red
= 10 kΩ ±1 %, 50 ppm/K

A TCR of 50 ppm/K is equivalent to a reference variation of 0.005% for each kelvin. It does not replace the manufacturer’s complete curve or incorporate self-heating, aging or additional tolerances.

TE Connectivity describes the reading orientation and function of the sixth band in this type marking.

Reliable reading procedure

1. Confirm that it is an axial resistor and not another banded component.
2. Count four, five or six bands.
3. Orient the component using distance, tolerance, and documentation.
4. Form the number with two digits in a four-band code or three digits in a five- or six-band code.
5. Apply the multiplier.
6. Calculate the limits with the tolerance.
7. Record the TCR if a sixth band exists.
8. Check the result with the data sheet or a multimeter when the circuit requires it.

What bands don’t tell you on their own

The code does not allow you to safely deduce the entire component sheet. In particular, it is not enough to know:

• the maximum admissible power;
• the maximum working voltage;
• the technology or composition;
• the temperature reduction curve;
• noise, stability or behavior in pulses;
• a special marking from the manufacturer.

Physical size can guide a family, but it does not replace component identification. To size a current limiter, also calculate dissipation with the LED resistor calculator.

SMD resistors and other codes

Surface-mount resistors usually use printed numbers, EIA-96 codes or proprietary markings. This procedure is limited to colored bands on axial resistors. It should also not automatically be applied to inductors, fuses or other components that use colors with different meanings.

Common errors

• Starting at the wrong end.
• Treat the third band of a five-band code as a multiplier.
• Forget multipliers smaller than one for gold and silver.
• Confuse tolerance with power.
• Assuming that the tolerance interval also covers temperature and aging.
• Trust only degraded, dirty or ambiguous colors.
• Measure within a circuit where other paths alter the reading.

Technical reference

IEC 60062 standardizes marking codes for resistors and capacitors. Tools in a Tab implements the generic 4-, 5- and 6-band scheme and processes the selection locally; it does not attempt to recognize a photograph or identify the manufacturer.