The standard size for most mid-tower and full-tower cases.
Use a tool like the PCPartPicker PSU Calculator or manufacturer calculators from MSI , Cooler Master , or Newegg to estimate your peak usage. how to buy a psu
It is widely recommended to choose a unit with 20% to 50% more wattage than your calculated total. This accounts for transient power spikes (sudden draws from modern GPUs) and future component upgrades. The standard size for most mid-tower and full-tower cases
Compact units designed for Small Form Factor (SFF) or Mini-ITX cases. how to buy a psu