Estimate the wattage your PC build needs and get a recommended PSU size.
How the PC Power Supply Calculator Works
Choosing the right power supply unit (PSU) means adding up the estimated wattage draw of every major component in your build, then adding a safety margin so the PSU isn't running at its absolute maximum capacity during peak load. Running a PSU too close to 100% load reduces efficiency, generates more heat, and shortens its lifespan.
Estimated Draw = CPU TDP + GPU TDP + (Drives × 15W) + (RAM Sticks × 5W) + (Fans × 3W) + 50W overhead
Recommended PSU = Estimated Draw × (1 + Headroom %), rounded up to the nearest common PSU size
Why Add Headroom?
A 30% headroom margin is a common recommendation because PSUs run most efficiently (and coolest) at 40-70% of their rated capacity, not at their absolute maximum. Headroom also gives you room to add components later or handle brief power spikes during heavy gaming or rendering loads.
Finding Your Component TDPs
Your CPU and GPU's TDP (Thermal Design Power, roughly equivalent to typical power draw) can be found on the manufacturer's official product page or specification sheet. High-end GPUs can range from 150W to over 450W, while CPUs typically range from 65W to 170W depending on the model.
❓ Frequently Asked Questions
How accurate is this PSU wattage estimate? ▼
It's a solid planning estimate based on typical component power draw, but actual power consumption varies by specific model, overclocking, and workload. Always check your GPU manufacturer's specific PSU recommendation for your exact card as a cross-reference.
Why does the calculator round up to specific PSU sizes like 650W or 750W? ▼
PSUs are manufactured in standard wattage tiers (450W, 550W, 650W, 750W, 850W, 1000W, and so on), so recommending the nearest common size reflects what you can actually buy.
Is it bad to buy a PSU with way more wattage than I need? ▼
Not dangerous, but it's inefficient use of money and the PSU will run at a lower, less efficient load percentage. A PSU rated for roughly 130-170% of your estimated draw (i.e., the 30-50% headroom range) is the generally recommended sweet spot.
Does PSU efficiency rating (80+ Bronze, Gold, Platinum) affect what wattage I need? ▼
Efficiency ratings affect how much electricity is wasted as heat (and your power bill), not the wattage capacity itself — a higher efficiency rating is a good idea, but doesn't change the wattage calculation shown here.
Should I include peripherals like monitors or speakers in this calculation? ▼
No — monitors, speakers, and other USB-powered peripherals draw power from the wall or their own power source, not from your PC's internal power supply, so they shouldn't be included in this estimate.
🏆 About This Tool — Accuracy & Trust
🔒 Data Privacy: All calculations run entirely within your browser using JavaScript. Nothing you enter here is ever transmitted to our servers, stored, sold, or shared.
📐 Accuracy Note: This tool uses standard, widely published formulas and guidelines. Results are estimates for informational purposes; for financial, medical, or engineering decisions, consult a licensed professional.
📅 Last Updated: September 2026.