Add up to 20 resistors in series using Ω, kΩ or MΩ for circuit analysis and electricity calculations, with a diagram and running total.

How to use

Enter each resistor value. Choose Ω, kΩ or MΩ for that row. Complete every row to calculate.

Use Add resistor or a row's Remove button to match your circuit. The tool accepts one to twenty resistors.

Read Equivalent resistance. Choose its display unit. Highlight a resistor to locate it in the diagram without changing your values.

Open Show the steps to see each resistance in ohms and the running total.

Copy result includes the resistor list and total. Reset clears the values and restores the starting row count and units.

Science

Series resistors form one path. Their equivalent resistance is the sum of their values. A zero-ohm element adds nothing to that sum.

This model treats each resistor as an ideal fixed value. It excludes contact resistance, component tolerance, heating and power rating.

Use the same unit before adding. A kiloohm is 1000 ohms and a megaohm is 1,000,000 ohms. The circuit picture shows connections, not physical size.

A blank row is missing information. Enter zero explicitly to represent an ideal wire.

Formulas

Series equivalent: R_eq = R1 + R2 + … + Rn; all resistances in Ω

Unit conversion: R(Ω) = R(kΩ) × 1000 = R(MΩ) × 1,000,000

Single resistor: R_eq = R1

Ideal wire: Adding 0 Ω leaves R_eq unchanged

Examples

100 Ω, 220 Ω and 330 Ω: 650 Ω. The three values add to 650 Ω.

1 kΩ, 470 Ω and 0.002 MΩ: 3470 Ω = 3.47 kΩ. Convert to 1000, 470 and 2000 Ω before adding.

0 Ω and 100 Ω: 100 Ω. The ideal wire contributes no resistance.

One 4.7 kΩ resistor: 4.7 kΩ. A one-element series path has that element's resistance.

0 Ω and 0 Ω: 0 Ω. Both entries are explicit ideal wires. The zero result is valid.

Assumptions

This model treats each resistor as an ideal fixed value. It excludes contact resistance, component tolerance, heating and power rating.

Limitations

This model treats each resistor as an ideal fixed value. It excludes contact resistance, component tolerance, heating and power rating.

References

OpenStax University Physics Volume 2, 10.2: Resistors in Series and Parallel

BIPM: SI prefixes

NIST SP 811, Chapter 4: SI units and prefixes