PC Power Supply Calculator
Enter your component wattages to find your total power draw, get a PSU recommendation with safety margin, and see which 80 PLUS tier makes sense for your build.
Last updated: May 2026
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Enter component wattages to get a PSU recommendation.
Recommended PSU = (sum of all components) x (1 + margin%)
How to choose the right PSU wattage for your PC build
A PSU is one component where undersizing causes real damage and oversizing is just mild inefficiency. The calculation is straightforward: add up the TDP values of every component, then add a safety margin. A 20% margin is the practical standard for most builds. That margin covers startup inrush current, aging capacity loss, and the gap between rated TDP and actual peak draw.
The GPU is typically the dominant draw in a gaming PC. An RTX 4070 has a TDP of 200 W but can spike to 250 W under sustained gaming load. High-end cards like the RTX 4090 have a rated TDP of 450 W. If you are running Resizable BAR with an aggressive power limit override, real board power can approach 600 W. For those cards, a 1000 W PSU is not excessive.
PSU wattage reference table
| PSU wattage | Typical build | 80 PLUS minimum |
|---|---|---|
| 350 W | Mini-ITX, no discrete GPU | Bronze |
| 500 W | Budget gaming, GTX 1660 class | Gold |
| 650 W | Mid-range, RTX 3060 / 4060 | Gold |
| 750 W | RTX 3070 / 4070, i7 / Ryzen 7 | Gold |
| 850 W | RTX 3080 / 4080, i9 / Ryzen 9 | Gold |
| 1000 W | RTX 3090 / 4090, extreme OC | Platinum |
Frequently Asked Questions
Why do I need a safety margin? Why not buy exactly what I need?
PSU capacity degrades over time as capacitors age. A brand-new 500 W PSU might deliver 500 W reliably, but after 3 years of use, especially under heat, effective capacity can drop 10-20%. Component peak draw during startup and heavy load spikes also exceeds the rated TDP. A CPU running at 95 W TDP can pull 130-150 W during a benchmark. Running a PSU near its maximum continuously shortens its lifespan significantly and increases failure risk. A PSU operating at 50-80% of rated capacity runs cooler, quieter, and lasts longer.
What is TDP and is it the same as actual power draw?
TDP stands for Thermal Design Power. It is the amount of heat a cooling solution must be able to dissipate, not necessarily the actual power drawn from the wall. For CPUs, TDP is usually close to typical workload power draw. For GPUs, the relationship is less predictable. The RTX 4090 has a 450 W TDP, but board power measurements in GPU-intensive workloads with power limits removed can approach 600 W. AMD and Nvidia both use TDP and TGP (Total Graphics Power) figures that reflect sustained gaming loads, not peak transient spikes. When sizing a PSU for a high-end GPU, add 10-25% to the quoted TGP figure for headroom.
Does a bigger PSU waste electricity at idle?
No, a larger PSU does not draw more power just because it has higher capacity. A 1000 W PSU powering a 100 W system draws roughly 100 W plus conversion losses, not 1000 W. However, PSU efficiency is load-dependent. Most 80 PLUS units are most efficient between 50-80% load and least efficient below 20% load. A 1000 W PSU with a 200 W draw operates at 20% load, which may be 3-5 percentage points less efficient than the same system running a 400 W PSU at 50% load. The difference is small in absolute terms, but if you are optimizing for electricity cost or heat output, matching PSU wattage to roughly twice your typical load is the practical sweet spot.
Is modular vs non-modular PSU relevant to power consumption?
No. The modular vs non-modular distinction affects cable management only, not efficiency ratings. A fully modular 80 PLUS Gold PSU and a non-modular 80 PLUS Gold PSU of the same wattage deliver the same efficiency. The 80 PLUS certification is based on electrical conversion efficiency measured at the PSU output, entirely independent of whether the cables are permanently attached or removable. Choose modularity based on your case size and how much cable management flexibility you need, not for any power draw reason.
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Installation fully sized: explore all electrical calculators.