Calculator Inputs
Example Data Table
These sample combinations show how band colors convert into resistance and tolerance ranges.
| Band 1 | Band 2 | Multiplier | Tolerance | Nominal | Minimum | Maximum |
|---|---|---|---|---|---|---|
| Yellow | Violet | Red | Gold | 4.7 kΩ | 4.465 kΩ | 4.935 kΩ |
| Brown | Black | Orange | Gold | 10 kΩ | 9.5 kΩ | 10.5 kΩ |
| Red | Red | Brown | Brown | 220 Ω | 217.8 Ω | 222.2 Ω |
| Green | Blue | Black | Silver | 56 Ω | 50.4 Ω | 61.6 Ω |
Formula Used
Nominal resistance: R = ((10 × Band1) + Band2) × Multiplier
Absolute tolerance: ΔR = R × (Tolerance ÷ 100)
Minimum resistance: Rmin = R - ΔR
Maximum resistance: Rmax = R + ΔR
Series network: Req = Quantity × R
Parallel network: Req = R ÷ Quantity for identical resistors.
This page also compares your selected resistor with an optional target value and plots the resistance band visually for faster checking.
How to Use This Calculator
- Select the first and second band colors to define the two significant digits.
- Choose the multiplier band to scale the digit pair into ohms, kilo-ohms, mega-ohms, or higher.
- Select the tolerance band to calculate the acceptable minimum and maximum resistance values.
- Optionally choose a resistor quantity and connection mode to estimate identical series or parallel networks.
- Optionally enter a target resistance to measure how far the selected resistor differs from your design goal.
- Press Calculate Resistor Value to display results above the form and render the Plotly chart.
- Use the CSV or PDF buttons after calculation to export the current output for documentation or review.
Frequently Asked Questions
1. What do the four resistor bands represent?
The first two bands are significant digits. The third band is the multiplier. The fourth band shows tolerance, which defines the allowed resistance variation from nominal.
2. How is the nominal resistance calculated?
Combine the first two band digits into one number, then multiply that value by the multiplier band. For example, yellow-violet-red becomes 47 × 100 = 4700 ohms.
3. Why are minimum and maximum values important?
Real resistors are not exact. Minimum and maximum values help you verify whether the chosen component still keeps your circuit inside acceptable operating limits.
4. What does a missing tolerance band mean?
A missing tolerance band is commonly treated as ±20%. This wider tolerance is typical for older or less precise resistor parts.
5. Why does this calculator include series and parallel modes?
Designers often combine identical resistors to reach a needed equivalent value or power handling target. These modes estimate that equivalent resistance quickly.
6. Can I compare the selected resistor against a target value?
Yes. Enter an optional target resistance and unit. The calculator returns the percentage deviation between the resistor’s nominal value and your target.
7. What does the Plotly graph show?
The graph plots minimum, nominal, and maximum resistance. It can also plot the equivalent network range and a target reference line when supplied.
8. Does this replace datasheets or measured testing?
No. Temperature, aging, power dissipation, measurement accuracy, and manufacturing details still matter. Use the calculator for fast estimation and verification support.