Two-Resistor Combination Solver
Best series or parallel pair from your E12/E24 drawer to hit any target resistance — exhaustive search, exact arithmetic.
The achieved error is the NOMINAL error — your parts still have their own ±5/±10 % tolerance. When a precise absolute value matters, measure and hand-match; when only a ratio matters (dividers, gain-set), put both resistors of the ratio in the same combo style so they drift together.
Two-Resistor Combination Solver computes the best series or parallel pair from standard values to hit a non-standard target — free, instant and private in your browser. Calibrators, repairers matching odd legacy values and designers avoiding special orders use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Two-Resistor Combination Solver
Two-Resistor Combination Solver computes the best series or parallel pair from standard values to hit a non-standard target using the standard engineering relation: exhaustive search over E12/E24 pairs: series R1+R2 and parallel R1·R2/(R1+R2), minimising error. Worked live: 13.7 kΩ comes out as 12 kΩ + 1.8 kΩ within 0.7 % from an E24 drawer. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Two-Resistor Combination Solver
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Two-Resistor Combination Solver?
- ✓Implements the real formula — exhaustive search over E12/E24 pairs: series R1+R2 and parallel R1·R2/(R1+R2), minimising error — with the substitution shown, not a black box
- ✓Built for calibrators, repairers matching odd legacy values and designers avoiding special orders
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate two-resistor combination?+
The best series or parallel pair from standard values to hit a non-standard target follows exhaustive search over E12/E24 pairs: series R1+R2 and parallel R1·R2/(R1+R2), minimising error. For example, 13.7 kΩ comes out as 12 kΩ + 1.8 kΩ within 0.7 % from an E24 drawer. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Series or parallel — which combination is better?+
Whichever lands closer; the solver tries both. Practically, series pairs are easier to assemble on through-hole and parallel pairs spread power across two packages — useful when the target also runs warm.
The nominal error is tiny — is my combination really that accurate?+
Only nominally. Each part still carries its own ±5/±10 % tolerance, so measure-and-match when absolute accuracy matters. For pure ratios, build both halves of the ratio the same way so their errors track.
Is the Two-Resistor Combination Solver free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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