Parallel Resistance Calculator
Find equivalent resistance for parallel branches. 1/Rtotal = 1/R1 + 1/R2 + ... + Rn. Three 100 Ω resistors in parallel give 33.333 Ω. Informational only.
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How to combine parallel resistors
- Enter two or more positive resistances separated by commas.
- Each value is one branch between the same two nodes.
- Read equivalent ohms and the branch count.
- For series sums use the series resistance page. Nothing is uploaded.
Parallel resistance
Reciprocal sum of branches
| Rule | 1/Rtotal = 1/R1 + 1/R2 + ... + 1/Rn |
|---|---|
| Voltage | Same across each parallel branch |
| Current | Splits by conductance |
| Equal example | Three 100 Ω give 33.333 Ω |
| Two equal | Two identical R give R/2 |
| Approval | Informational. Not a circuit sign-off. |
Reciprocal formula
Add reciprocals: 1/Rtotal = 1/R1 + 1/R2 + ... + Rn. Three 100 Ω branches: 3/100 gives Rtotal = 100/3 ≈ 33.333 Ω. Two equal resistors in parallel halve the value.
Conductance view
Conductance G = 1/R adds directly in parallel. This is the dual of the series sum rule.
Series is different
Series resistors sum directly. Do not mix rules on one form. The series page handles the additive case.
Limits
Ideal resistors, no mutual coupling.
The formula runs in this tab. CZNull does not receive the numbers.
Informational only. Not wiring, code, or manufacturer approval. See the disclaimer.