Temperature Coefficient Calculator

Temperature effects in electrical components were documented as early as the 1820s with Humphry Davy's observation that conductor resistance increases with temperature. Matthiessen's rule (1864) formalized the relationship for pure metals: ρ(T) = ρ₀·(1 + α·ΔT), with α(Cu) = 0.004/°C. This is why copper wire resistance at 75°C is 20% higher than at 25°C — a consideration in every cable sizing calculation.

The Bureau of Standards (now NIST) cataloged TCR values of common resistor materials in the 1920s-40s, establishing the alloy families still used today: Constantan (~20 ppm/°C, the reference for precision wirewound), Nichrome (~70 ppm/°C, higher-temperature applications), Evanohm (~5 ppm/°C, for metrology grade). The 1950s invention of bulk metal-foil resistors (Vishay/Sfernice) pushed precision TCR below 0.5 ppm/°C — the gold standard for voltage-reference divider networks today.

Capacitors follow EIA/CEI class designations: C0G (a.k.a. NP0) has ±30 ppm/°C, essentially the best of any capacitor type — used in oscillator tanks and precision timing; X7R has ±15% over its operating range — fine for bypass but unusable for timing; Y5V has +22/-82% — only suitable for bulk decoupling. Z5U and Y5V are essentially junk for anything precision.

Enter the component's nominal value, TCR in ppm/°C (from the datasheet), reference temperature T₁, and operating temperature T₂. The tool applies the linear first-order model V(T₂) = V(T₁) × (1 + TCR × (T₂ − T₁) / 10⁶), returning the drifted value, absolute change, percent change, and temperature delta.

Real-world considerations: TCR is often specified as a maximum over the full operating range rather than a single number — actual TCR varies with temperature. For precision, use components with specified TCR curves and measure the complete circuit's drift end-to-end rather than relying on paper specifications. Self-heating from dissipated power adds to ambient — a 1 W resistor running at 500 mW easily sees 30-50°C self-heating. Everything runs client-side; no values leave your browser.