Resistors in series simply add, because current must pass through each one in turn. It is the easiest way to build a value you don’t have in your parts drawer.
How to use the Series Resistor Calculator
- Calculate
- Target total resistance
- Resistor 1
- Resistor 2
- Resistor 3
- Resistor 4
- Resistor 5
- Resistor 6
- Resistor 7
- Resistor 8
- Resistor 9
- Resistor 10
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the mode and enter the resistors (0 = unused).
Inputs explained
| Field | What to enter |
|---|---|
| Calculate | Choose one: Total resistance, Missing resistor |
| Target total resistance | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 1 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 2 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 3 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 4 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 5 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 6 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 7 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 8 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 9 | Units: Ω, kΩ, MΩ, mΩ |
| Resistor 10 | Units: Ω, kΩ, MΩ, mΩ |
What each result means
- Total resistance = [Resistor 1] + [Resistor 2] + [Resistor 3] + [Resistor 4] + [Resistor 5] + [Resistor 6] + [Resistor 7] + [Resistor 8] + [Resistor 9] + [Resistor 10]
- Missing resistor = [Target total resistance] – ([Resistor 1] + [Resistor 2] + [Resistor 3] + [Resistor 4] + [Resistor 5] + [Resistor 6] + [Resistor 7] + [Resistor 8] + [Resistor 9] + [Resistor 10])
Example values
How the main result changes when Target total resistance changes and everything else stays at the example values above:
| Target total resistance (Ω) | Total resistance (Ω) |
|---|---|
| 5 | 7.9 |
| 7.5 | 7.9 |
| 10 | 7.9 |
| 12.5 | 7.9 |
| 15 | 7.9 |
| 20 | 7.9 |
Formula
R_total = Σ R_i · Missing: R_x = R_target − Σ R_i
Worked example
Inputs — Calculate: Total resistance; Resistor 1: 1 Ω; Resistor 2: 2.2 Ω; Resistor 3: 4.7 Ω; Resistor 4: 0 Ω; Resistor 5: 0 Ω; Resistor 6: 0 Ω; Resistor 7: 0 Ω; Resistor 8: 0 Ω; Resistor 9: 0 Ω; Resistor 10: 0 Ω.
Results — Total resistance = 7.9 Ω.
Key terms
- Series circuit
- Components connected one after another.
Frequently asked questions
Does order matter in series?
No.
Is the current the same in each resistor?
Yes.
What happens to tolerance?
Absolute errors add; the relative tolerance stays about the same.
Why use series resistors?
To make a value, divide voltage or share power.