Series & Parallel Resistor Calculator
Calculate equivalent resistance for series and parallel circuits
Resistor Values
R1
Ω
R2
Ω
R3
Ω
Calculation Results
Equivalent Resistance
600 Ω
Sum of all resistances
Current Flow (at 12V)
0.02 A
Using Ohm's Law: I = V / R
Power Dissipation
0.24 W
Total power across all resistors
Series Circuit
Current flows through each resistor one after another
Rtotal = R1 + R2 + R3 + ...
Parallel Circuit
Current divides between multiple paths
1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ...
Resistance Formulas
Series Resistance
Rtotal = R1 + R2 + R3 + ... + Rn
In a series circuit, the total resistance is simply the sum of all individual resistances.
Parallel Resistance
1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn
In a parallel circuit, the reciprocal of the total resistance equals the sum of reciprocals of individual resistances.
Two Resistors in Parallel (Shortcut)
Rtotal = (R1 × R2) / (R1 + R2)
For exactly two resistors in parallel, you can use this product-over-sum formula.
