Case 1
- First resistance R1 (Ω)
- 100Ω
- Second resistance R2 (Ω)
- 220Ω
320.000Ω
Open with these valuesSeries Resistor Calculator
320.000Ω
Result: 320.000 ΩResistors in series add: 100 Ω and 220 Ω make 320 Ω, more than either part. The same current has to push through both in turn, so their opposition piles up. The mirror image is worth keeping in mind — capacitors in series get smaller, not larger.
The numbers at a glance
Held fixed: First resistance R1 (Ω) 100.000 Ω.
| Second resistance R2 (Ω) (Ω) | Result (Ω) |
|---|---|
| 100.000 | 200.000 |
| 200.000 | 300.000 |
| 220.000Your value | 320.000 |
| 300.000 | 400.000 |
| 400.000 | 500.000 |
Worked examples
Case 2
- First resistance R1 (Ω)
- 1000Ω
- Second resistance R2 (Ω)
- 470Ω
1,470.000Ω
Open with these valuesCase 3
- First resistance R1 (Ω)
- 4.7Ω
- Second resistance R2 (Ω)
- 2.2Ω
6.900Ω
Open with these valuesHow it's calculated
R = R1 + R2
- StepEnter both resistances in ohms — a 1k resistor is 1000 Ω.
- StepAdd the two values; nothing else enters the sum.
- ResultRead the total; it is always larger than either resistor.
Reference table
| R1 (Ω), R2 (Ω) | What it is | Total (Ω) |
|---|---|---|
| 1, 1 | two matched parts | 2 |
| 4.7, 2.2 | two E12 values | 6.9 |
| 10, 10 | double one of them | 20 |
| 50, 50 | double one of them | 100 |
| 100, 220 | the default pair | 320 |
| 1000, 470 | 1k plus 470 Ω | 1470 |
Questions
How do two resistors in series combine?
They simply add: R = R1 + R2. For 100 Ω and 220 Ω that is 320 Ω. Resistors are in series when they sit end to end on one path, so the very same current flows through both.
Why is the series resistance larger than either resistor?
Because the current has to push through both parts one after the other, so the obstacles add up. There is only one path, and every resistor on it opposes the current in turn. The total is therefore always above the larger of the two.
What happens when both resistors are equal?
The total is exactly double one of them, because R plus R is 2R. Two 100 Ω resistors give 200 Ω and two 10 Ω resistors give 20 Ω. It is the easy way to build a value twice as large from matched parts.
How is series different from parallel?
It is the opposite. In series you add the values and the total grows above either part; in parallel the total drops below the smaller one. Series adds resistance, parallel reduces it.
Where is series resistance used?
Limiting current to protect an LED, building a precise value from standard resistors on hand, and making voltage dividers where the supply splits in proportion to the two values. Any time parts sit on one path so the same current flows through each, their resistances add.
Sources and last check
Information, not professional advice.