Parallel Resistor & Pair Finder
Calculate equivalent resistance for parallel circuits or find the best E-series resistor pairs to achieve a specific non-standard target resistance.
About
Precise resistance values are required for feedback loops, voltage regulators, and sensitive timing circuits. Often, the calculated ideal resistance does not exist in standard manufacturing series (E12, E24, E96). Engineers solve this by placing two or more common resistors in parallel.
This configuration reduces the total resistance below the smallest individual resistor in the network. This tool performs two functions: computing the equivalent resistance of a given network, and the inverse operation - finding the optimal pair of standard components to achieve a specific target value (e.g., creating 3.14 kฮฉ from standard parts).
Formulas
The inverse of the equivalent resistance is the sum of the inverses of individual resistances:
For exactly two resistors, the product-over-sum formula applies:
Reference Data
| Series | Precision | Values per Decade | Common Examples |
|---|---|---|---|
| E12 | ยฑ10% | 12 | 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 |
| E24 | ยฑ5% | 24 | 1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8... |
| E96 | ยฑ1% | 96 | 1.00, 1.02, 1.05, 1.07... |