Resistor Color Code Calculator

This professional tool helps engineers, students, and makers decode and encode resistor color bands with absolute clarity. Read 3, 4, 5, or 6-band resistors; compute nominal value, tolerance range, and temperature coefficient. Or input a numeric resistance and get the exact color bands, optimized for mobile and assistive technologies.

Results

Resistor visualization with color bands Dynamic illustration of the resistor body and the selected bands.
Nominal resistance —
Tolerance —
Min → Max —
Temperature coefficient —
Color code —
Shareable URL —

Data Source and Methodology

Primary reference: IEC 60062:2016 (Marking codes for resistors and capacitors), International Electrotechnical Commission, 2016. View IEC 60062.

Secondary reference for preferred numbers: IEC 60063 (Preferred number series for resistors and capacitors). View IEC 60063.

Practical cross-check: Digi-Key — Resistor Color Code Calculator. View resource.

All computations strictly follow the formulas and data provided by these sources.

The Formulas Explained

$$ R = \Big(\sum_{i=1}^{k} d_i \cdot 10^{k-i} \Big)\cdot 10^{M} $$ where k = 2 for 3/4-band, k = 3 for 5/6-band; d_i are significant digits, and M is the multiplier exponent.

$$ R_{\min} = R \cdot \Big(1 - \frac{\tau}{100}\Big), \quad R_{\max} = R \cdot \Big(1 + \frac{\tau}{100}\Big) $$ where τ is the tolerance percentage.

Temperature coefficient (ppm/°C) indicates change per degree: $$ \Delta R \approx R \cdot \alpha \cdot \Delta T \cdot 10^{-6} $$ where α is the tempco in ppm/°C and ΔT is temperature change in °C.

Glossary of Variables

  • Band 1, 2, 3: Significant digit colors mapping to digits 0–9.
  • Multiplier (M): Power of ten determined by the multiplier band, including gold (10^-1) and silver (10^-2).
  • Tolerance (τ): Allowed percentage deviation; “None” (no band) means ±20%.
  • Temperature coefficient (α): Change per °C in ppm (parts per million) for 6-band resistors.
  • R (Ω): Nominal resistance in ohms.
  • Rmin, Rmax (Ω): Minimum and maximum resistance limits considering tolerance.
  • E-series: Preferred number sets (E12/E24) used to select commercially available values.

How It Works: A Step-by-Step Example

Goal: Decode a 5-band resistor with colors Brown, Black, Green, Red, Brown.

  1. Digits: Brown=1, Black=0, Green=5 → 105.
  2. Multiplier: Red → 10^2, so R = 105 × 10^2 = 10,500 Ω = 10.5 kΩ.
  3. Tolerance: Brown → ±1%. Therefore Rmin = 10.5 kΩ × (1 − 0.01) = 10.395 kΩ; Rmax = 10.5 kΩ × (1 + 0.01) = 10.605 kΩ.
  4. If a 6th band exists, read it as the temperature coefficient (e.g., Red = 50 ppm/°C).

Frequently Asked Questions (FAQ)

How do I read 3, 4, 5, and 6-band resistors?

3-band: 2 digits + multiplier (default ±20%). 4-band: 2 digits + multiplier + tolerance. 5-band: 3 digits + multiplier + tolerance. 6-band: 5-band + temperature coefficient.

Why are gold and silver used?

Gold and silver primarily indicate lower multipliers (×0.1 and ×0.01) and also common tolerances (±5% and ±10%).

What if one band is faded or burned?

Use the remaining bands plus measurement if possible. Compare the computed nominal value to E-series to estimate the missing band. When in doubt, replace with a safe, equal or higher tolerance part and validate in-circuit.

Can the first digit be black (0)?

Practically no for standard coding; the leading digit is typically non-zero. This tool will warn you if an uncommon combination is selected.

How accurate is the temperature coefficient?

The tempco band provides a nominal ppm/°C value per IEC 60062. Real performance depends on the resistor technology (e.g., metal film vs. carbon film) and the operating conditions.

How do E-series impact my selection?

E-series help you select commercially available values. Use E12 (10%) or E24 (5%) snapping to ensure your encoded value matches standard production parts.

Tool developed by Ugo Candido. Content verified by CalcDomain Editorial Team.
Last reviewed for accuracy on: .