Electrical calculator
Resistor Color Code Calculator
Decode resistor color bands to find resistance value and tolerance.
About the resistor color code calculator
The resistor color code calculator decodes the 4-band resistor color bands to find the resistance value and tolerance range.
How to use this calculator
- 1
Select band colors
Select the color for each of the 4 bands.
- 2
View results
See the resistance value, tolerance range, and color code explanation.
How the calculation works
Resistance = (band1 × 10 + band2) × multiplier. Tolerance defines the range of actual values.
Example: Red (2), Violet (7), Orange (×1k), Gold (±5%) = 27kΩ ±5%.
Safety first
These calculators provide estimates based on standard formulas and NEC guidelines. Always verify results with a licensed electrician before making installations. Electrical work can be dangerous — never work on live circuits, and always follow local building codes and regulations.
Understanding electrical units
Voltage (V) is electrical pressure, current (A) is flow rate, resistance (Ω) opposes flow, and power (W) is the rate of energy use. Ohm's law (V = I × R) relates the first three, while power formulas (P = VI, P = I²R) connect all four. Understanding these relationships is key to safe electrical design.
Important limitations
This tool provides a mathematical estimate based only on the values entered. It does not account for regulations, taxes, lender fees, market conditions, or individual circumstances. Results are for planning purposes only — consult a qualified professional for regulated, medical, financial, or construction decisions.
Frequently asked questions about resistor color code calculator
How accurate is the resistor color code calculator?+
The calculation follows the displayed formula and retains full numeric precision before formatting the result.
Can I use the result professionally?+
Use it as a planning estimate. Confirm regulated, medical, financial, or construction decisions with a qualified professional.