Series Resistance Calculator
Calculate series resistance step by step: R_total = R1 + R2 + … + Rn.
In short
Formula: R_total = R1 + R2 + … + Rn.
Total resistance
650 Ω
- Resistors counted
- 3
What this calculator does
Calculate series resistance step by step: R_total = R1 + R2 + … + Rn. Worked example, questions and limitations included.
Use it to turn R1, R2, R3 (optional), R4 (optional), and the other shown inputs into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this electrical calculation.
Inputs and what they mean
- R1
- — number value.
- R2
- — number value.
- R3 (optional)
- — number value.
- R4 (optional)
- — number value.
- R5 (optional)
- — number value.
- Supply voltage (optional)
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
The same current flows through every resistor in series.
Blank optional boxes are skipped; negative values are rejected.
With a supply voltage, current = V ÷ R_total.
R_total = R1 + R2 + … + Rn.
Inputs used: R1, R2, R3 (optional), R4 (optional), R5 (optional), Supply voltage (optional).
Worked example
100 Ω + 220 Ω + 330 Ω
- 100 + 220 + 330 = 650 Ω.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Up to five resistors.
- Ignores tolerance and temperature drift.
- Ideal wires with zero resistance assumed.
- Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
- The result depends on the values you enter for this series resistance calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
Why is the total always larger than any single resistor?
Current has to pass through every resistor in turn, so each one adds opposition. Check the formula, example, and limitations on this page before using the result for a real electrical decision.
How is voltage shared?
Each resistor drops V × (its R ÷ total R). That is the principle behind the voltage divider calculator.
What if one resistor fails open?
The whole series chain stops conducting, because there is only one path for current. Check the formula, example, and limitations on this page before using the result for a real electrical decision.
How do I use the Series Resistance Calculator?
Enter the required values for R1, R2, R3 (optional), R4 (optional), R5 (optional), and the other fields shown. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Series Resistance Calculator use?
R_total = R1 + R2 + … + Rn. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Series Resistance Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Related tools
Calculate electrical power step by step: P = V × I = I² × R = V² ÷ R (DC or resistive AC using RMS values).
Calculate voltage divider step by step: Vout = Vin × R2 ÷ (R1 + R2).
Calculate resistance step by step: R = V ÷ I, or for a conductor R = ρ × L ÷ A (A in m²).