To calculate your wattage needs manually, you need to estimate the peak power consumption of your core components.
If you are building a modern PC with an RTX 40-series card, look for a PSU labeled ATX 3.0 or PCIe 5.0 ready . These units come with the native 12VHPWR cable and are built specifically to handle the power spikes of new GPUs. watt psu calculator
Modern high-end graphics cards (specifically the RTX 30-series and 40-series) can experience micro-second power spikes that draw 2x or 3x their rated power. If your PSU doesn't have enough overhead, these spikes will trip the PSU’s protection and shut off your PC instantly. To calculate your wattage needs manually, you need