About this Resistor Calculator
A resistor's colored bands are a compact code for a numerical value, but reading them by eye becomes easy to mix up when five- and six-band parts are involved.
The Resistor Calculator in this script converts selected band colors into significant digits, a multiplier, tolerance, and—where present—a temperature coefficient. Three- and four-band resistors use two significant digits, while five- and six-band versions use three.
The multiplier scales those digits by a power of ten; a separate tolerance band tells you the allowed manufacturing range around the nominal resistance. A sixth band can add temperature coefficient in ppm/°C.
This makes the tool useful at a workbench, in electronics classes, or when identifying parts pulled from a board where the printed value is not available.
What Is a Resistor Calculator?
A Resistor Calculator decodes the standardized color bands printed around through-hole resistors. For a three- or four-band part, the script forms a two-digit number from the first two colors and multiplies it by 10 raised to the multiplier value.
For a five- or six-band part, it uses three significant digits before the multiplier. Tolerance is read from the appropriate later band, and the sixth band on a six-band resistor can represent temperature coefficient.
For example, brown-black-brown represents 10 multiplied by 10¹, or 100 Ω; on a three-band resistor the source treats the missing tolerance band as ±20%. The calculator therefore translates a visual code into the electrical specification the bands represent.
Reading Your Results
That number is the Resistor answer for this particular combination of inputs. The method does not change between runs, so you can rely on it as a fixed reference point.
Try changing a single figure and comparing the two results: the size of the shift is often more informative than the number itself.
How to use this calculator
The calculator determines the resistance value, tolerance, and temperature coefficient where applicable.
For a 3-band resistor
For a 4-band resistor
For a 5-band resistor
For a 6-band resistor
General Formula
Example
Resistor Colour Code
| Colour | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1,000 | — |
| Yellow | 4 | ×10,000 | — |
| Green | 5 | ×100,000 | ±0.5% |
| Blue | 6 | ×1,000,000 | ±0.25% |
| Violet | 7 | ×10,000,000 | ±0.1% |
| Grey | 8 | — | ±0.05% |
| White | 9 | — | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Read the bands from the end where they are grouped closest together.
Common E12 Resistor Values
| Value | Value | Value | Value |
|---|---|---|---|
| 1.0 Ω | 10 Ω | 100 Ω | 1 kΩ |
| 1.2 Ω | 12 Ω | 120 Ω | 1.2 kΩ |
| 1.5 Ω | 15 Ω | 150 Ω | 1.5 kΩ |
| 2.2 Ω | 22 Ω | 220 Ω | 2.2 kΩ |
| 3.3 Ω | 33 Ω | 330 Ω | 3.3 kΩ |
| 4.7 Ω | 47 Ω | 470 Ω | 4.7 kΩ |
| 6.8 Ω | 68 Ω | 680 Ω | 6.8 kΩ |
The E12 series provides 12 values per decade at ±10% tolerance.
Resistor Network Formulas
| Configuration | Formula |
|---|---|
| Series | R_total = R₁ + R₂ + ... + Rₙ |
| Parallel (two) | R_total = (R₁ × R₂) ÷ (R₁ + R₂) |
| Parallel (n) | 1/R_total = 1/R₁ + 1/R₂ + ... + 1/Rₙ |
| Equal parallel resistors | R_total = R ÷ n |
| Voltage Divider | V_out = V_in × R₂ ÷ (R₁ + R₂) |
Always confirm the power rating; a resistor dissipating more than its rating will fail.
Factors Affecting Your Resistor Result
Band order is the first thing to get right. The reference guidance says to read from the end where the colored bands are grouped most closely, because reversing a resistor can change both the significant digits and the multiplier.
The number of bands also changes the decoding rule: three and four bands use two significant digits, while five and six bands use three.
Multiplier color has a large effect because it changes the power of ten; confusing red with brown can move the nominal resistance by a factor of ten. Tolerance does not change the printed nominal value but defines the range in which the real component may fall.
A 100 Ω resistor at ±5%, for example, may legitimately measure roughly 95–105 Ω. Temperature coefficient matters when resistance changes with operating temperature. Dirt, faded paint, lighting, and similar colors can also make physical identification uncertain, so a multimeter is a useful cross-check when the bands are hard to distinguish.
Benefits of Using the Resistor Calculator
- Decode three-, four-, five-, and six-band resistors without memorizing every digit, multiplier, tolerance, and temperature-coefficient color.
- Reduce errors caused by moving the decimal place incorrectly when a multiplier represents a large or fractional power of ten.
- See the nominal resistance and tolerance together, which is more useful than reading the resistance value without its allowed range.
- Check classroom exercises or component selections against the standard color-code table shown on the page.
- Identify a likely resistor value before confirming it with a meter when printed markings are absent or too small to read.
Frequently asked questions
How do I know which end of the resistor to read first?
The page's reference note says to start from the end where the bands are grouped more closely. A tolerance band such as gold or silver is also commonly positioned toward the far end, helping identify the reading direction.
What is different about a five-band resistor?
It uses three significant-digit bands instead of two, followed by a multiplier and tolerance band. That extra significant digit allows higher-precision nominal values to be encoded.
What does resistor tolerance mean?
Tolerance is the permitted percentage difference between nominal and actual resistance. A 1 kΩ resistor with ±5% tolerance can be within roughly 950 Ω to 1,050 Ω and still meet that specification.
What does the sixth band represent?
In the six-band scheme used by the script, the sixth band represents temperature coefficient in parts per million per degree Celsius, indicating how much resistance can shift with temperature.
Why might a multimeter reading differ from the calculator value?
The calculator decodes the nominal specification. The physical resistor can vary within its tolerance, temperature can shift resistance, and measuring it while connected in a circuit can allow other components to affect the reading.
Final Words
The point of the Resistor Calculator is not just to return a number, but to help you decode three-, four-, five-, and six-band resistors without memorizing every digit, multiplier, tolerance, and temperature-coefficient color. One important consideration is that band order is the first thing to get right.
If the situation changes, use the Resistor Calculator again and reduce errors caused by moving the decimal place incorrectly when a multiplier represents a large or fractional power of ten.
Disclaimer
This calculator provides estimates for general informational and educational purposes only and should not be treated as financial, medical, legal, or professional advice. Results depend entirely on the accuracy of the figures you enter.
Always verify important decisions with a qualified professional, official documentation, or your financial institution before acting on any result shown here.
Related Calculators
Precise age calculator that determines your exact age in years, months, days, hours, and minutes from your birth date. Calculate age differences between dates, upcoming birthdays, and various time-related calculations with detailed breakdowns and multiple format options.
Use CalculatorCalculate work hours, overtime, time sheets, hourly wages, and time tracking for payroll and project management purposes.
Use CalculatorCalculate duration between two times or dates with precise time measurements.
Use CalculatorCalculate love compatibility percentage based on names for entertainment purposes.
Use CalculatorCalculate height conversions between different units and predict adult height based on current age.
Use CalculatorRoll virtual dice with customizable sides and quantities for games and probability.
Use CalculatorConvert shoe sizes between different international sizing systems and standards.
Use CalculatorCalculate heat index and apparent temperature based on air temperature and humidity levels.
Use CalculatorCalculate Grade Point Average (GPA) for academic performance tracking with support for different grading scales and credit systems.
Use Calculator