Skip to content
ENExplore Calculators

Series Resistance Calculator

Work out series resistance instantly with clear inputs, formula shown and shareable results.

About Series Resistance Calculator

Resistors in series carry the same current, so their resistances add: Rtotal = R1 + R2 + R3. The current is set by Ohm's law on the total, and each resistor drops a voltage in proportion to its own resistance, which is exactly how a voltage divider works.

Formula

Series resistance

Rtotal = R1 + R2 + R3; I = V / Rtotal

Worked example

With the default values below, Series Resistance Calculator returns Total resistance of 1,690.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Resistor 1
220 Ω
Resistor 2
470 Ω
Resistor 3
1,000 Ω
Applied voltage
12 V

Results

Total resistance
1,690.00 Ω
Current through the string
0.00710 A
Largest resistor's share of voltage
59.17% %
Total power dissipated
0.09 W

Step by step

  1. 1Values used
  2. 2Series resistance
  3. 3Total resistance= 1,690.00 Ω
  4. 4Current through the string= 0.00710 A
  5. 5Largest resistor's share of voltage= 59.17 %
  6. 6Total power dissipated= 0.09 W

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why do series resistances add?

The same current flows through each, so the voltage drops add, and by Ohm's law that means the resistances add.

Which resistor gets hottest?

The largest one. Power in each is I squared times R, and since current is common, dissipation is proportional to resistance.

Related Calculators

Series Resistance Calculator – Calculate Total resistance