Open the side panel of your computer case (you may need a screwdriver).
If you don't want to open the case, you can often find the specs digitally: how do i check my psu wattage
The (often circled or in a larger font) is your PSU’s rated wattage. Pay special attention to the +12V rail – modern CPUs/GPUs rely on it. If the +12V amps × 12 is far below the total, it’s a low-quality PSU. Open the side panel of your computer case
Most consumer PSUs report wattage via software because there is no data cable from the PSU to the motherboard. However: your PSU is likely ≥500W.
The result gives . Compare to your system: if the calculator says 500W and your PC runs fine, your PSU is likely ≥500W.