Quick answer
Series resistances add: R_total = R₁ + R₂ + …. Resistors of 100, 220 and 330 Ω in series total 650 Ω.
Enter resistor values separated by commas. The calculator returns the total resistance and the count.
Related tools: Voltage Divider Calculator: Output voltage of a two-resistor divider. RLC Impedance Calculator: Impedance and phase angle of a series RLC circuit. RMS Voltage Calculator: Convert between RMS, peak and peak-to-peak voltage of a sine wave.
How to use the Series Resistance Calculator
- Type resistor values (Ω), for example 100, 220, 330.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Resistor values (Ω) | Text, such as 100, 220, 330 | — |
Formula and method
Formula
R_total = R₁ + R₂ + …
IEEE-754 double precision; shown to the decimals indicated.
Use the same unit for every value.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Resistor values (Ω) = 100, 220, 330.
| Result | Value |
|---|---|
| Total resistance | 650 Ω |
| Number of resistors | 3 |
Example 2
Inputs: Resistor values (Ω) = 4.7, 10.
| Result | Value |
|---|---|
| Total resistance | 14.7 Ω |
| Number of resistors | 2 |
Example 3
Inputs: Resistor values (Ω) = 1000.
| Result | Value |
|---|---|
| Total resistance | 1,000 Ω |
| Number of resistors | 1 |
The first line is the headline result (total resistance). Below it the series Resistance Calculator lists number of resistors, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Voltage sharing
In a series circuit the same current flows through each resistor and the voltage divides in proportion to resistance. On 13 V across 650 Ω the current is 20 mA and the drops are 2 V, 4.4 V and 6.6 V.
Practical points
The total is always larger than the largest resistor. Values must be positive. If one resistor fails open, the entire circuit stops conducting.
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Resistor values (Ω): left empty shows "Enter resistor values (ω)." beside that field and no result.
Choosing between the Series Resistance Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Voltage Divider Calculator](/engineering/voltage-divider-calculator/) | input voltage, r1 and r2 | Output voltage |
| [RLC Impedance Calculator](/engineering/rlc-impedance-calculator/) | resistance, inductance and capacitance | Impedance |
| [RMS Voltage Calculator](/engineering/rms-voltage-calculator/) | i know the and voltage | RMS voltage |
| [Parallel Plate Capacitor Calculator](/engineering/parallel-plate-capacitance-calculator/) | plate area, plate separation and relative permittivity εr | Capacitance |
| [Current Divider Calculator](/engineering/current-divider-calculator/) | total current, r1 and r2 | Current through R1 |
Background: electrical circuits
Ohm's law links voltage, current and resistance: V = I × R, so I = V ÷ R and R = V ÷ I. Power is P = V × I, which also equals I² × R and V² ÷ R.
These relations hold for ohmic components, where resistance is constant. Diodes and transistors are non-linear, and in AC circuits with reactive parts impedance (Z) takes the place of resistance. Check component ratings and local electrical code before relying on any calculation.
Assumptions and limitations
- Values must be positive
Use results as engineering estimates and check them against the governing standards, safety factors and a qualified engineer's judgement before relying on them.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for resistor values (Ω) to confirm this.
Frequently asked questions
What is the series formula for capacitors?
They combine like parallel resistors.
Does order matter?
No. Series resistances add, so 100 + 220 + 330 is 650 Ω in any order.
How can I make a non-standard value?
Combine standard resistors in series.
What does the Series Resistance Calculator calculate?
Total resistance of resistors in series. It returns Total resistance and Number of resistors.
What formula does the Series Resistance Calculator use?
R_total = R₁ + R₂ + …. Use the same unit for every value.
What do I need to enter in the series Resistance Calculator?
You enter Resistor values (Ω).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Values must be positive.
What is an example of a series Resistance result?
With resistor values (Ω) 100, 220, 330, the total resistance is 650 Ω.
Can I rely on this calculator for a decision?
Use results as engineering estimates and check them against the governing standards, safety factors and a qualified engineer's judgement before relying on them. For this calculator in particular: Values must be positive.
Related calculators
- Voltage Divider Calculator — Output voltage of a two-resistor divider.
- RLC Impedance Calculator — Impedance and phase angle of a series RLC circuit.
- RMS Voltage Calculator — Convert between RMS, peak and peak-to-peak voltage of a sine wave.
- Parallel Plate Capacitor Calculator — Capacitance of two parallel plates.
- Current Divider Calculator — Current through each of two parallel resistors.
- Inductive Reactance Calculator — Reactance of an inductor at a frequency.
Sources
- OpenStax, University Physics Volume 2 (Rice University): electricity, circuits and thermodynamics
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.