How Much Real Wattage Does Your PC Need (Calculator Explained)
How to calculate it by adding up each component's consumption, with the right safety margin.
Before buying a power supply, calculating the real wattage you need avoids both falling short and spending unnecessarily more.
The simple method: add up by component
| Component | Approximate consumption |
|---|---|
| Mid-range processor | 65-125W |
| High-end processor | 125-250W |
| Mid-range graphics card | 150-250W |
| High-end graphics card | 250-450W+ |
| Rest (board, RAM, disks, fans) | ~50-100W combined |
The exact figure for each component is on the manufacturer's spec sheet (look for "TDP" for processor and graphics card) — add them all up to get your estimated base consumption.
Add the safety margin
To the total, add an extra 20-30% — this covers transient power spikes and future upgrades without needing to change the power supply soon.
Online calculation tools
There are online wattage calculators (search "PSU calculator") where you enter your exact components and they automatically calculate the recommended wattage, already with safety margin included — more convenient than manually adding up each component.
Tip: if you plan to upgrade the graphics card in the near future, calculate the wattage thinking about that future component too, not just your current build — this avoids having to change the power supply again soon.
Frequently asked questions
Where do I find the exact consumption of my components?
On the manufacturer's spec sheet, looking for the 'TDP' figure for processor and graphics card — they're the two components that contribute the most consumption to the total.
Why add an extra 20-30% margin?
To cover transient power spikes of modern components (which can briefly exceed their average consumption) and to leave margin for future upgrades without changing the power supply soon.