This PSU calculator does two jobs that matter before you spend money. As a power supply calculator, it estimates your system's real power draw so you can size the unit correctly — the job people also reach for a wattage calculator or PC power supply calculator to do. And as a CPU GPU bottleneck calculator, it compares your components' performance tiers to tell you which one is holding the other back.
What size PSU do I need?
Add your graphics card's board power to your processor's peak package power, then add roughly 60–100 W for the motherboard, memory, drives and fans. Size the power supply so that total sits at roughly 65% of its rating on a mid-range build, rising to about 80% on a very high-wattage one — the PSU wattage calculator above applies exactly that rule, keeping you in the unit's efficiency band with headroom for transient spikes.
Modern GPUs draw brief spikes well above their rated board power, which is what trips an undersized supply into shutting down even when the average draw looks fine. Running at around 60% load also puts most units near their peak efficiency, which means less heat and quieter fans. For anything at 850 W or above, use an ATX 3.x supply with a native 12V-2x6 connector rather than an adapter.
What is a bottleneck, and does it matter?
A bottleneck is when one component limits the performance the rest of your system could deliver. A CPU bottleneck means your processor cannot feed frames fast enough for your graphics card; a GPU bottleneck means the opposite. Some imbalance is normal and usually fine.
Being GPU-limited is generally the healthier state: it means you are getting everything your processor can give, and a graphics upgrade will translate straight into frame rate. CPU limits bite hardest at low resolutions and in simulation-heavy games — which is exactly what GTA 6 is expected to be, with its dense traffic, crowds and physics.
What PSU do I need? How many watts is enough
Most gaming PCs need a 550 W to 850 W power supply. A build with an RTX 5060 or RX 7600 is comfortable on 550 W, an RTX 5070 or RX 7800 XT wants 650–750 W, an RTX 4090 wants around 850–1050 W, and an RTX 5090 build needs 1200 W or more.
The calculator above works this out from your exact parts rather than a generic table, because the processor matters too — pairing a 450 W graphics card with a 253 W processor needs noticeably more headroom than pairing it with a 65 W one.
Is a 750W or 1000W power supply overkill?
Not necessarily, and it costs you nothing in running expense. A power supply only draws what the components request, so a 1000 W unit in a 400 W system uses roughly the same electricity as a 650 W unit would. Oversizing costs money upfront, not on your bill.
A 750 W supply is sensible headroom for most mid-to-high builds. A 1000 W unit is only genuinely overkill if you never plan to upgrade the graphics card — and given how GPU power draw has climbed each generation, that headroom often pays for itself at the next upgrade.
How to check PSU wattage on your current PC
The wattage is printed on the power supply's own label, usually on the side facing into the case. Windows does not report it, and no software can read it reliably, so you either check the label, look up your exact PSU model number, or check the specification sheet for a pre-built system.
If you are trying to check PSU wattage without opening the computer, the specification sheet for your pre-built model or the original order confirmation is the fastest route. For a custom build, the model number on the invoice will tell you.
How to balance a build
- Match tiers, not brands — a mid-range GPU pairs with a mid-range CPU
- Spend the bigger share of the budget on the GPU if you play at 1440p or 4K
- Spend more on the CPU if you play at 1080p, at high refresh rates, or in simulation-heavy games
- 16 GB of RAM is the floor in 2026; 32 GB is the comfortable target
- Run memory in dual-channel — two sticks, not one
- Buy an NVMe SSD for the OS and your current games; texture streaming depends on it
- Do not buy a power supply on price alone — it is the part that can take others with it
Typical component power draw
| Component | Typical draw | Notes |
|---|---|---|
| Flagship GPU (RTX 5090, RTX 4090) | 450–575 W | Large transient spikes; ATX 3.x strongly advised |
| High-end GPU (RTX 5080, RX 7900 XTX) | 300–360 W | 750–850 W supply is the usual pairing |
| Mid-range GPU (RTX 5070, RX 7800 XT) | 200–265 W | 650–750 W is comfortable |
| Entry GPU (RTX 5060, RX 7600) | 115–165 W | 550 W is usually plenty |
| High-end CPU (i9, Ryzen 9) | 170–253 W | Peak package power, not idle draw |
| Mid-range CPU (i5, Ryzen 5) | 65–181 W | X3D parts run cooler than their raw tier suggests |
| Memory, drives, fans, board | 60–120 W | Scales with drive count and cooling |