Resistor Ratio and Preferred-Value Combinations
Enter R1/R2 or two resistances to compare one-resistor, series-denominator and parallel-denominator preferred-value solutions.
Inputs and reverse calculation
Calculated results
| Current R1/R2 | 0.5 |
|---|---|
| Single-resistor denominator | 33K Ω ÷ 68K Ω = 0.49 |
| Single-solution mismatch | 3.03 % |
| Two series resistors in denominator | 10K Ω ÷ (10K Ω + 10K Ω) = 0.5 |
| Series-solution mismatch | 0 % |
| Two parallel resistors in denominator | 10K Ω ÷ (22K Ω ∥ 220K Ω) = 0.5 |
| Parallel-solution mismatch | 0 % |
How to interpret the result
Editing R1 or R2 preserves those resistances and calculates their ratio. Editing the target ratio, changing the series or taking the reciprocal searches preferred values again. In both combination solutions, the two-resistor network is in the denominator.
Formulas and units
Target x=R1/R2; series solution x≈A/(B+C); parallel solution x≈A/(BC/(B+C)). The original App ranks candidates by (max(actual/target,target/actual)−1)×100%, rather than signed deviation.
Worked example
With R1=1000 Ω and R2=2000 Ω, the ratio is 0.5. One reciprocal toggle gives 2; another returns to 0.5. Wire a proposed solution according to its displayed values and topology.
Scope and limitations
Uses the supplied E6–E192 values and original floor-candidate algorithm. Ratios are limited to 10⁻⁶–10⁶ to avoid zero scaling and fixed upper limits in the original solver. Solutions optimize nominal ratio only; tolerance, temperature drift, noise and dissipation are excluded. Check availability before selection.
Common questions
Does editing a resistance apply the reciprocal again?
No. Toggling the checkbox applies the reciprocal once; a later R1/R2 edit calculates from the two resistances, following the App’s last-edited-field behavior.
Does zero mismatch guarantee an exact physical ratio?
Zero mismatch means only that the nominal values produce the target ratio. Physical resistors still have tolerance and temperature coefficients.
Related tools
Formula and data sources
Rebuilt from the extracted Electrodoc Pro 5.2 specification. Added, inferred and corrected behavior is identified in the limitations. Updated 2026-11-13.