Resistor Color Code Calculator

Resistors are among the most common components in electronic circuits, and nearly all through-hole resistors are marked with colored bands that encode their resistance value and tolerance. Learning to read these bands — or using this calculator — saves time and prevents circuit errors.

How Resistor Color Coding Works

The IEC 60062 standard defines the color coding system used worldwide. Each color corresponds to a digit (0–9), a multiplier, or a tolerance value. The bands are read from one end of the resistor to the other, starting from the end closer to a group of bands.

Color-to-Digit Mapping

4-Band Resistors

A 4-band resistor has:

1. Band 1: First significant digit
2. Band 2: Second significant digit
3. Band 3: Multiplier
4. Band 4: Tolerance

Formula: R = (Band1 × 10 + Band2) × Multiplier

Example: Brown – Black – Red – Gold

• Brown = 1, Black = 0 → 10
• Red = ×100
• Gold = ±5%
• R = 10 × 100 = 1,000 Ω = 1 kΩ ±5%

5-Band Resistors

A 5-band resistor has:

1. Band 1: First significant digit
2. Band 2: Second significant digit
3. Band 3: Third significant digit
4. Band 4: Multiplier
5. Band 5: Tolerance

Formula: R = (Band1 × 100 + Band2 × 10 + Band3) × Multiplier

Example: Brown – Green – Black – Brown – Brown

• Brown = 1, Green = 5, Black = 0 → 150
• Brown = ×10
• Brown = ±1%
• R = 150 × 10 = 1,500 Ω = 1.5 kΩ ±1%

5-band resistors are used for precision components (usually ±1% or better tolerance).

Understanding Tolerance

Tolerance tells you how much the actual resistance may deviate from the nominal value. For a 1 kΩ resistor:

• Gold (±5%): actual range is 950–1,050 Ω
• Silver (±10%): actual range is 900–1,100 Ω
• Brown (±1%): actual range is 990–1,010 Ω

For most digital logic circuits, ±5% resistors (gold band) are sufficient. For precision analog circuits, op-amp feedback networks, or ADC reference voltage dividers, use ±1% or better.

Practical Tips

• Identify orientation: The tolerance band (gold/silver) is usually on one end, making it easy to determine reading direction.
• Verify with a multimeter: Always measure critical resistors before installation in precision circuits.
• E-series values: Resistors are only made in standard E-series values (E12, E24, E48, E96). A calculated “resistance” that doesn’t match a standard value may indicate a reading error.
• Surface-mount (SMD) resistors: SMD resistors use a 3-digit or 4-digit numerical code, not color bands. This calculator is for through-hole resistors only.

Common Resistor Values

Reference

IEC 60062:2016 — Marking codes for resistors and capacitors. International Electrotechnical Commission. Geneva, Switzerland.