PC Power Supply Wattage Calculator

Why PSU wattage matters

An undersized PSU causes random reboots under load, shortened component life, and can damage other parts on failure. An oversized PSU wastes money but doesn't hurt — modern 80 Plus units run efficiently across most of their range.

The 20% headroom rule

Take your actual measured load and add 20% headroom. Why:

• PSUs degrade ~3-5% capacity per year — a brand-new 750W unit may only deliver 650W after 3 years.
• Transient spikes (GPU power excursions, CPU boost) can briefly exceed your PSU's continuous rating by 50%+ on high-end chips.
• Future upgrades — adding more drives, better cooling, swapping for a higher-end GPU.
• PSU efficiency peaks at 50-60% load. Running at 90% load is hotter, louder, and less efficient.

80 Plus efficiency tiers

• 80 Plus White (84% efficient): Budget tier. OK for low-power builds.
• 80 Plus Bronze (85% efficient): Entry mainstream. Acceptable for office and entry gaming.
• 80 Plus Gold (90% efficient): Sweet spot for most enthusiast builds.
• 80 Plus Platinum (92% efficient): Premium. Worth it for 24/7 workstations or hot environments.
• 80 Plus Titanium (94% efficient): Flagship. Diminishing returns over Platinum for most users.

Recommended brands

Stick to the tier-1 OEMs and their reputable rebrands: Seasonic, Corsair (RM/HX/AX), EVGA (G+/G3/Supernova), be quiet! (Straight Power, Dark Power), Super Flower. Avoid no-name brands and unlisted models even if cheaper — PSU is the one part where saving $30 can cost you $1,500 in damaged components.

Modular vs non-modular

• Non-modular: All cables permanently attached. Cheapest. Messy cable management.
• Semi-modular: 24-pin and CPU cables fixed; PCIe and peripherals detachable. Best value.
• Fully modular: Every cable detachable. Cleanest builds and easiest upgrades. ~$20-40 premium.

For tested PSUs and PC components, see our computing reviews.