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Resistor Calculator

Calculate resistor values from color bands and find series/parallel resistance combinations.

A resistor calculator decodes color bands to find resistance values and calculates total resistance for series and parallel circuits.

In Color Code mode, select the colors of each band on your resistor to decode its value. In Series/Parallel mode, enter comma-separated resistance values and the connection type to find the combined resistance.

Examples

Brown-Black-Red-Gold resistor

Band 1 = 1, Band 2 = 0, Multiplier = x100. Value = 10 x 100 = 1,000 ohms (1 k-ohm), 5% tolerance.

Three 100-ohm resistors in parallel

1/R = 1/100 + 1/100 + 1/100 = 3/100. R = 100/3 = 33.33 ohms.

Frequently Asked Questions

How do I read resistor color bands?
Hold the resistor with the tolerance band (gold/silver) on the right. Read left-to-right: first band is the first digit, second band is the second digit, third band is the multiplier, and the last band is tolerance.
When should I use series vs parallel?
Series connections add resistances (increase total). Parallel connections reduce total resistance below the smallest individual resistor. Series is for current-limiting; parallel is for current-sharing or lowering resistance.
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Quick Tips

  • •Use the mnemonic "Bad Beer Rots Our Young Guts But Vodka Goes Well" for color band order (Black=0 through White=9).
  • •Always check resistor values with a multimeter before soldering into a circuit.

A resistor calculator decodes color bands to find resistance values and calculates total resistance for series and parallel circuits.

How to Use This Calculator

In Color Code mode, select the colors of each band on your resistor to decode its value. In Series/Parallel mode, enter comma-separated resistance values and the connection type to find the combined resistance.

Understanding the Formula

Color code: Value = (Band1 x 10 + Band2) x Multiplier. Series: R_total = R1 + R2 + R3 + ... Parallel: 1/R_total = 1/R1 + 1/R2 + 1/R3 + ...

Examples

Brown-Black-Red-Gold resistor

Band 1 = 1, Band 2 = 0, Multiplier = x100. Value = 10 x 100 = 1,000 ohms (1 k-ohm), 5% tolerance.

Three 100-ohm resistors in parallel

1/R = 1/100 + 1/100 + 1/100 = 3/100. R = 100/3 = 33.33 ohms.

Frequently Asked Questions

How do I read resistor color bands?

Hold the resistor with the tolerance band (gold/silver) on the right. Read left-to-right: first band is the first digit, second band is the second digit, third band is the multiplier, and the last band is tolerance.

When should I use series vs parallel?

Series connections add resistances (increase total). Parallel connections reduce total resistance below the smallest individual resistor. Series is for current-limiting; parallel is for current-sharing or lowering resistance.

Assumptions & Limitations

  • Color band values follow the IEC 60062 standard; actual resistance varies within the tolerance band.
  • Assumes ideal resistors — real-world values are affected by temperature, aging, and manufacturing variation.