PSU Calculator

A PSU (Power Supply Unit) calculator estimates the total power consumption of your PC components and recommends the appropriate power supply wattage. Every component in your computer — from the CPU and GPU to RAM, storage drives, and fans — draws power from the PSU. If your power supply cannot deliver enough wattage, your system will crash, restart randomly, or fail to boot entirely. Conversely, an oversized PSU wastes money and operates at lower efficiency. The ideal PSU runs at 50-80% of its rated capacity, where modern 80 PLUS certified units achieve their highest efficiency. This calculator accounts for real-world factors that simpler tools ignore: overclocking headroom, GPU transient power spikes (which can briefly reach 2× the rated TDP), capacitor aging over time, and the efficiency losses inherent in AC-to-DC power conversion.

The calculation starts by summing the TDP (Thermal Design Power) of each component. For CPUs, TDP ranges from 45W for budget chips to 350W for workstation processors. GPUs range from 75W to 575W for the latest flagship cards. RAM uses about 3-5W per stick, SATA drives 5-10W, NVMe drives 5-8W, and fans 2-5W each. Overclocking adds 10-30% on top. A 20% safety margin is applied for system stability and future headroom. For GPUs in the RTX 40/50 series, transient power spikes are a critical factor — these cards can briefly draw 1.5-2× their rated TDP in millisecond-scale bursts. ATX 3.0/3.1 power supplies are designed to handle these spikes; older ATX 2.x units may trigger over-current protection and shut down. The recommended PSU wattage is then rounded up to the nearest standard PSU size (450W, 550W, 650W, 750W, 850W, 1000W, 1200W, or 1500W).