# Parallel Resistor Calculator

URL: https://speedycalculator.com/calculators/physics/resistors-parallel/
Last updated: 2026-10-25

> The parallel resistor calculator finds the equivalent resistance of up to four resistors connected in parallel, and the series total for comparison. Enter values in ohms, kilohms or megohms.

## Inputs

- R₁ (Ω, kΩ, MΩ)
- R₂ (Ω, kΩ, MΩ)
- R₃ (0 = none) (Ω, kΩ, MΩ)
- R₄ (0 = none) (Ω, kΩ, MΩ)

## Results

- Parallel resistance
- Series resistance

## Formula

```
1/R = 1/R₁ + 1/R₂ + 1/R₃ + 1/R₄
Series: R = R₁ + R₂ + R₃ + R₄
```

## Explanation

In parallel, current has several paths, so the total resistance is always lower than the smallest resistor.

### How to use the Parallel Resistor Calculator

- **R₁**
- **R₂**
- **R₃ (0 = none)**
- **R₄ (0 = none)**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Add the reciprocals of each resistance and take the reciprocal of the sum. Leave unused resistors at 0.

### Inputs explained

FieldWhat to enterR₁Units: Ω, kΩ, MΩR₂Units: Ω, kΩ, MΩR₃ (0 = none)Units: Ω, kΩ, MΩR₄ (0 = none)Units: Ω, kΩ, MΩ

### Example values

How the main result changes when **R₁** changes and everything else stays at the example values above:

R₁ (Ω)Parallel resistance (Ω)5037.49097549.983910059.976812568.151915074.963820085.6669

## Worked example

Inputs — R₁: 100 Ω; R₂: 220 Ω; R₃ (0 = none): 470 Ω; R₄ (0 = none): 0 Ω.

Results — **Parallel resistance = 59.9768 Ω**; Series resistance = 790 Ω.

## FAQ

**What is the shortcut for two resistors?**
R₁R₂ ÷ (R₁ + R₂), “product over sum”.

**Why is parallel resistance smaller?**
Each extra path lets more current flow for the same voltage.

**What formula does the Parallel Resistor Calculator use?**
1/R = 1/R₁ + 1/R₂ + 1/R₃ + 1/R₄.