Resistor Color Code Calculator

This tool decodes standard 4-band, 5-band, and 6-band resistor color codes into numeric resistance values, tolerance, and temperature coefficient (for 6-band). It converts band inputs—represented as digit/multiplier/tolerance values—into a human-readable result with proper SI prefixes (Ω, kΩ, MΩ) and scientific notation where appropriate.

Use it when bands are faded, poorly printed, or difficult to distinguish (e.g., red vs. orange, gold vs. yellow). It’s also invaluable during PCB reverse-engineering, component verification in prototyping, educational labs, and rapid BOM validation—reducing human error in interpreting color sequences under time pressure or suboptimal lighting.

Band 1 and Band 2 are the first two significant digits of the resistance value. Band 3 is the multiplier (power-of-ten exponent), e.g., 3 = ×10³ = 1k. Band 4 indicates tolerance: 1 = ±1%, 2 = ±2%, 5 = ±5%, 10 = ±10%. For example, inputs 1, 0, 3, 5 decode to 10 × 10³ Ω = 10 kΩ ±5%.

Standard resistor color codes map each band to discrete integer values (0–9 for digits/multipliers; specific integers like 1, 2, 5, 10 for tolerance). Non-integer inputs would not correspond to any physical color—so the tool enforces valid EIA-standardized values to ensure accuracy and prevent misinterpretation.

Common tolerances are: 1 → ±1% (brown), 2 → ±2% (red), 5 → ±5% (gold), 10 → ±10% (silver). Some precision resistors use 0.1% (purple), 0.25% (blue), or 0.5% (green), but those require 5- or 6-band decoding—this calculator supports them via extended input interpretation in advanced mode.

For 5-band resistors, enter the third digit as Band 3, the multiplier as Band 4, and tolerance as Band 5. For 6-band, Band 6 represents temperature coefficient (e.g., 15 = 15 ppm/°C). The calculator automatically formats results with appropriate precision and includes TC in the output table when Band 6 is provided.

Ensure all inputs are integers within valid ranges: Bands 1–2 and 3 must be 0–9; Band 4 must be 1, 2, 5, or 10 (or 0.1, 0.25, 0.5 for high-precision 5/6-band). Also verify JavaScript is enabled—this tool relies on client-side execution. Empty or non-numeric fields will suppress output until corrected.

Yes—it verifies nominal value and tolerance compatibility. Cross-check the calculated resistance against standard E-series values (E12, E24, etc.) and confirm tolerance and power rating match your circuit’s requirements. Note: This tool does not assess power dissipation or voltage derating—those require separate thermal and electrical analysis.

Not directly in this version—but you can reverse-engineer it: extract significant digits, determine the nearest E-series value, identify the multiplier exponent, then map digits/tolerance to colors using the standard chart (e.g., 0=black, 1=brown… 9=white; gold=±5%, silver=±10%). A reverse lookup feature is planned for future updates.

The calculator provides mathematically exact decoding based on your inputs—no rounding or approximation is applied. However, real-world resistor accuracy depends on manufacturing tolerances, aging, temperature, and measurement conditions. Always validate critical values with a calibrated multimeter before final design sign-off.