Series Resistor Calculator
Resistors in series.
Open →
Energy
Parallel Resistor Calculator
Find the total resistance of resistors in parallel.
Total resistance
—
In parallel.
| Resistors used | — |
|---|---|
| — | |
| — | |
| — |
Show our math
Enter your figures above to see the step-by-step working.
Everything computed client-sideEverything computed client-side — nothing leaves this page
How the Parallel Resistor Calculator Works
Resistors in parallel share the current, so the total resistance is always less than the smallest one. Add the reciprocals (1 divided by each resistance) and take the reciprocal of the sum. Two 100-ohm resistors in parallel give 50 ohms; add more paths and the total keeps dropping.
A handy shortcut for two resistors is the product over the sum: R1×R2 ÷ (R1+R2). For equal resistors, the total is just one resistor divided by how many there are.
1 ÷ Rtotal = 1/R₁ + 1/R₂ + …
Frequently Asked Questions
How do you calculate parallel resistance?
Add the reciprocals of each resistance and take the reciprocal of the total. The result is always less than the smallest resistor.
Why is parallel resistance lower?
Each parallel path gives current another way to flow, so overall the circuit resists less than any single path.
Is there a shortcut for two resistors?
Yes — multiply the two values and divide by their sum: R1×R2 ÷ (R1+R2).
More From The Desk
Same plain method, different figuresResistor Color Code Calculator
Color bands to resistance.
Open →Capacitor Calculator
Stored energy and charge.
Open →Watt-Hours Calculator
mAh to watt-hours.
Open →Electricity Cost
Same plain method, different figures.
Open →