PC Power Supply (PSU) Wattage Calculator

Figure Out What Power Supply Your Build Actually Needs

Undersize a PSU and a new build randomly reboots under load or won't post with a power-hungry GPU attached; oversize it by too much and you're paying for headroom (and lower efficiency at light loads) you'll never use. This calculator adds up realistic power draw from your CPU, GPU, storage, RAM, fans, and cooling, then applies the same kind of headroom margin that PSU manufacturers themselves recommend, rounded to a wattage you can actually buy.

How to use it

• Pick your CPU's rough power class (or enter its exact TDP) and your graphics card from the list, or enter a custom GPU TDP if yours isn't listed.
• Add your RAM stick count, SSDs, HDDs, and case fan count — these are individually small but add up across a full build.
• Choose your cooling type and motherboard form factor, and check the boxes for RGB lighting or CPU/GPU overclocking if they apply.
• The recommended PSU wattage already includes headroom for power supply efficiency losses, momentary power spikes under load, and room to add a bigger GPU later — you don't need to add your own buffer on top.

Real-world use cases

Planning a new gaming PC build and needing a PSU wattage to shop for before pricing out the rest of the parts list. Checking whether an existing PSU has enough headroom before dropping in a significantly more powerful graphics card. Sanity-checking a pre-built PC's power supply against its listed specs before adding a GPU upgrade.

Frequently asked questions

Why is the recommended wattage higher than my components add up to?

Two reasons: PSUs run most efficiently at 40–70% of their rated load rather than near 100%, and modern GPUs draw brief power spikes well above their rated TDP under load. The 1.3× multiplier here accounts for both, which is the same general margin PSU manufacturers themselves build into their own calculators.

Does a higher-wattage PSU use more electricity?

No — a PSU only draws as much power as your components actually need at any moment. Wattage rating is a ceiling, not a fixed draw, so a higher-rated PSU running the same components uses essentially the same power (often slightly less, since it runs further from its inefficient upper limit).

What PSU efficiency rating should I buy?

80+ Bronze is the practical minimum for a modern build; 80+ Gold is the sweet spot for most gaming PCs, balancing price and efficiency. Platinum and Titanium mainly matter for systems that run under heavy load nearly continuously, where the efficiency gap actually shows up on an electricity bill.

Should I size a PSU for future upgrades?

It's reasonable to leave some extra headroom if you're planning a GPU upgrade within the PSU's lifespan, but sizing more than one full upgrade ahead usually just means paying for capacity you won't use for years, if ever.