EngineeringFormulaElectrical Engineering
Resistor Color Code Calculator
Decode 4-, 5-, and 6-band resistor color codes into resistance, tolerance range, and temperature coefficient.
This resistor color code calculator reads the colored bands on axial resistors and converts them into the nominal resistance in ohms, the tolerance percentage, and the minimum-to-maximum resistance range. Choose 4 bands for common general-purpose resistors, 5 bands for precision parts with three significant digits, or 6 bands when the final band gives temperature coefficient in ppm/°C.
Live Band Preview
Solution
Nominal Resistance
1 kΩ
±5%
Formula
R = significant digits × multiplier
Substitution
10 × 100 Ω = 1 kΩ
Result
Tolerance range: 950 Ω to 1.05 kΩ
Formula Sheet
- D₁, D₂, D₃Digit Bands
- MMultiplier
- TTolerance
- TCRTemperature Coefficient
Variables & Units
| Symbol | Variable | Description | Common Units |
|---|---|---|---|
| D₁, D₂, D₃ | Digit Bands | Color bands that represent the significant digits of the resistance value. | |
| M | Multiplier | Color band that multiplies the significant digits by a power of ten, with gold and silver for fractional multipliers. | |
| T | Tolerance | Allowed percentage variation from the nominal resistance. | |
| TCR | Temperature Coefficient | Sixth-band value showing resistance drift in parts per million per degree Celsius. |
How to Use This Calculator
- 01Select the number of bands on the resistor: 4, 5, or 6.
- 02Read the resistor from the end with the grouped bands; the tolerance band is often gold or silver and usually sits at the far right.
- 03Choose each visible band color in order from left to right.
- 04Select Calculate to see the nominal resistance, tolerance window, and temperature coefficient when a sixth band is present.
- 05Use the color lookup table below the examples if you are unsure whether a color is a digit, multiplier, tolerance, or temperature-coefficient band.
How the Formula Works
The first two bands on a 4-band resistor are significant digits, the third band is the multiplier, and the fourth band is tolerance. For example, brown-black-red-gold means 10 × 100 Ω = 1,000 Ω with ±5% tolerance.
Five-band and six-band resistors use three significant digits before the multiplier, which is common on precision resistors. A sixth band does not change the resistance value; it reports temperature coefficient, the expected resistance drift per degree Celsius.
The tolerance range is calculated from the nominal resistance: minimum = R × (1 − tolerance) and maximum = R × (1 + tolerance). This is the guaranteed window, not a measured value from the specific resistor in your hand.
The most common user mistake is reading the resistor backwards. Gold and silver normally appear as tolerance or multiplier bands, not first digit bands, so a band set that begins with gold or silver is a strong clue to turn the resistor around.
Worked Example 01
Common 1 kΩ resistor
Known
- Bands: Brown, Black, Red, Gold
- Digits: 1, 0
- Multiplier: Red = ×100
- Tolerance: Gold = ±5%
Formula
R = significant digits × multiplier
Substitution
R = 10 × 100 Ω
Result
R = 1 kΩ ±5%, range 950 Ω to 1.05 kΩ
Brown and black form the digits 10, red multiplies by 100, and gold gives a ±5% tolerance window.
Worked Example 02
Precision 10 kΩ resistor
Known
- Bands: Brown, Black, Black, Red, Brown
- Digits: 1, 0, 0
- Multiplier: Red = ×100
- Tolerance: Brown = ±1%
Formula
R = significant digits × multiplier
Substitution
R = 100 × 100 Ω
Result
R = 10 kΩ ±1%, range 9.9 kΩ to 10.1 kΩ
The 5-band layout uses three significant digits before the multiplier, which is why it can express precision values cleanly.
Worked Example 03
Six-band 100 Ω precision resistor with low drift
Known
- Bands: Brown, Black, Black, Black, Brown, Brown
- Digits: 1, 0, 0
- Multiplier: Black = ×1
- Tolerance: Brown = ±1%
- Temperature coefficient: Brown = 100 ppm/°C
Formula
Rmin,max = R × (1 ± tolerance)
Substitution
R = 100 × 1 Ω; range = 100 × (1 ± 0.01)
Result
R = 100 Ω ±1%, range 99 Ω to 101 Ω, TCR = 100 ppm/°C
The sixth band gives temperature drift, not another digit. This kind of part is common where the resistance value should remain stable as the circuit warms up.
Applications
- 01Identifying through-hole resistor values on breadboards, kits, and repair benches
- 02Checking tolerance range before using a resistor in an analog circuit
- 03Reading 5- and 6-band precision resistors used in measurement and reference circuits
- 04Confirming whether a resistor is suitable before using it with an LED Resistor Calculator or Ohm's Law Calculator result
Resistor Color Code Lookup Table
| Color | Digit | Multiplier | Tolerance | TCR |
|---|---|---|---|---|
| Black | 0 | ×1 | — | 250 ppm/°C |
| Brown | 1 | ×10 | ±1% | 100 ppm/°C |
| Red | 2 | ×100 | ±2% | 50 ppm/°C |
| Orange | 3 | ×1 k | — | 15 ppm/°C |
| Yellow | 4 | ×10 k | — | 25 ppm/°C |
| Green | 5 | ×100 k | ±0.5% | 20 ppm/°C |
| Blue | 6 | ×1 M | ±0.25% | 10 ppm/°C |
| Violet | 7 | ×10 M | ±0.1% | 5 ppm/°C |
| Gray | 8 | ×100 M | ±0.05% | 1 ppm/°C |
| White | 9 | ×1 G | — | — |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
Assumptions
- 01The resistor uses the standard axial resistor color code with bands read from left to right.
- 02Gold and silver are used only as multiplier or tolerance bands, not as significant digits.
- 03The calculator reports the specified tolerance window; it does not measure the actual resistor.
Where This Model Stops
- 01Does not identify SMD resistor markings or printed numeric codes.
- 02Does not resolve faded, ambiguous, or non-standard manufacturer band colors.
- 03Does not replace multimeter verification for critical repair, safety, or calibration work.
- 04Does not account for circuit context; a resistor measured in-circuit may read differently because other components are connected in parallel.
References
- [1]Resistor Color Code Calculator
DigiKey
Reference for 4-, 5-, and 6-band resistor layouts, digit colors, multipliers, tolerances, and ppm bands.
- [2]Resistor Color Code Calculator
Mouser Electronics
Industry calculator used for cross-checking color-band roles and common decode examples.
Frequently Asked Questions
How do I know which end of the resistor to start from?
Start from the end where the digit bands are grouped together. The tolerance band is often gold or silver and is usually separated slightly from the other bands, so it belongs on the right. If the first band appears to be gold, silver, or black, you may be reading the resistor backwards.
What is the difference between 4-band and 5-band resistors?
A 4-band resistor uses two significant digits, then a multiplier and tolerance. A 5-band resistor uses three significant digits, then a multiplier and tolerance, so it is common for tighter precision parts such as ±1% resistors.
What does the sixth band mean?
The sixth band is the temperature coefficient, usually stated in ppm/°C. It tells you how much the resistance is expected to drift as temperature changes; it does not change the nominal ohm value.
How is this different from the Ohm's Law Calculator?
This calculator identifies a physical resistor from its color bands. The Ohm's Law Calculator uses voltage, current, and resistance to solve a circuit relationship. A common workflow is to decode the resistor here first, then use that resistance value in Ohm's Law.
Why should I still measure a resistor with a multimeter?
Color bands give the specified nominal value and tolerance range, but they do not prove the exact part in your hand is healthy or still within tolerance. For repairs, calibration, or safety-critical work, remove one leg from the circuit and verify with a meter.