This calculator decodes standard 4-band axial resistor color bands into nominal resistance values, tolerance boundaries, and equivalent surface-mount device (SMD) marking codes. All calculations run client-side in your browser.

### Resistance Formula and SMD Mapping Axial lead resistors use colored stripes to indicate resistance value and tolerance under standard IEC 60062 conventions. For 4-band resistors, the tool applies the following equations:

- **Nominal Resistance:** $\text{Resistance } (\Omega) = (\text{Digit } 1 \times 10 + \text{Digit } 2) \times \text{Multiplier}$ - **Minimum Acceptable Resistance:** $\text{Min Value} = \text{Resistance} \times (1 - \text{Tolerance } / 100)$ - **Maximum Acceptable Resistance:** $\text{Max Value} = \text{Resistance} \times (1 + \text{Tolerance } / 100)$ - **3-Digit EIA SMD Code:** $\text{SMD Code} = \text{Digit } 1 \parallel \text{Digit } 2 \parallel \log_{10}(\text{Multiplier})$ For example, a $10\text{ k}\Omega$ resistor with digits 1 and 0 followed by multiplier $10^3$ yields SMD marking code 103.

### Worked Numeric Example Using standard 4-band components: - **1st Band (Digit 1):** Brown (Value: 1) - **2nd Band (Digit 2):** Black (Value: 0) - **Multiplier Band:** Orange ($\times 1,000$ / 1k) - **Tolerance Band:** Gold ($\pm 5\%$)

**Calculated Output:** 1. Base value: $(1 \times 10 + 0) \times 1,000 = 10,000\ \Omega$ ($10.00\text{ k}\Omega$). 2. Lower bound: $10,000 \times 0.95 = 9,500\ \Omega$ ($9.50\text{ k}\Omega$). 3. Upper bound: $10,000 \times 1.05 = 10,500\ \Omega$ ($10.50\text{ k}\Omega$). 4. SMD Equivalent Marking: 103.

### Client-Side Processing Note All band lookups, mathematical conversions, and unit formatting operate locally inside your browser session. No data or component queries are sent to external servers.