The Resistor Wattage Calculator uses Ohm's Law fundamentals: P = V² / R (power from voltage and resistance) or P = I² × R (power from current and resistance). If you provide voltage and current, it computes P = V × I and then derives resistance. For reliability, always select a resistor with at least twice the calculated power (50% derating). Example: If dissipation = 0.25W, choose 0.5W or 1W resistor. This tool supports bulk analysis — ideal for BOM verification, LED current limiting, voltage divider networks, and power supply design. The batch upload accepts thousands of rows, outputs wattage, recommended derated wattage, voltage, current, and resistance. Ensure input validation prevents negative or zero values. Use this tool to prevent resistor overheating, circuit failure, and enhance design efficiency.

📐 Formulas: P = V × I | P = I² × R | P = V² / R | Derating factor = Power × 2