Resistor Calculator
Calculate resistor value from color bands or find series/parallel combinations.
Resistor Calculator
Calculate resistor value from color bands or find series/parallel combinations.
Engineering Calculation
ℹ️ Used for basic engineering ratio and product calculations
Disclaimer
Results provided by this calculator are for informational and educational purposes only. They are based on the values you enter and standard formulas, and should not be considered financial, medical, legal, or professional advice. Always consult a qualified professional before making important decisions based on these results. Roughtools makes no warranties regarding the accuracy or completeness of these calculations for your specific situation.
Frequently Asked Questions
Pro Tips
Always verify critical calculations with a second method or source — for important decisions, this tool provides a starting point, not a final answer.
Input accuracy determines output accuracy. Use precise values rather than rough estimates for the most useful results.
Run the calculation multiple times with slightly different inputs to understand the sensitivity of the result to your assumptions.
For professional, financial, medical, or legal decisions, always confirm results with a qualified professional before acting.
When to Use This Calculator
Use the Resistor Calculator for fast, accurate calculations without installing any software.
Understand the formula and see how changing inputs affects the result for educational purposes.
Get a quick estimate before performing more detailed analysis or consulting a professional.
Accessible from any device — no app to install, no account required, works offline after loading.
Run multiple scenarios quickly by changing one input at a time to understand sensitivities.
About the Resistor Calculator
This resistor calculator decodes standard 4-band, 5-band, and 6-band resistor color codes to find resistance value and tolerance, and calculates the equivalent resistance of any series or parallel combination of resistors. Select the color bands from the dropdown menus or enter resistor values for combination calculations. Built for electronics students, hobbyists, technicians, and engineers working with discrete resistor components.
How to Use the Resistor Calculator
- 1
For color band decoding: select the number of bands (4, 5, or 6) and choose each band color from the dropdowns.
- 2
See the resistance value in ohms, kilohms, or megohms and the tolerance percentage.
- 3
For series resistance: enter resistor values separated by commas — total R = R1 + R2 + R3...
- 4
For parallel resistance: enter resistor values — total R = 1/(1/R1 + 1/R2 + 1/R3...).
- 5
Mix series and parallel sections by calculating each section separately and combining.
Related Calculators
View all →Ohms Law Calculator
Calculate voltage, current, resistance, or power using Ohm's Law.
Voltage Drop Calculator
Calculate voltage drop in electrical wire runs for any circuit length and load.
Electricity Calculator
Calculate electricity costs, kilowatt-hours, and energy consumption for devices.
Binary Calculator
Perform binary arithmetic and convert between binary, decimal, hex, and octal.
Scientific Notation Calculator
Convert numbers to and from scientific notation and perform operations.
Your input is processed locally in your browser and is never stored, transmitted, or shared with any server. See our Privacy Policy.