PSU sizing guide 2026: how many watts does your PC need?

The quickest way to size a PSU: add the processor's maximum package power and the graphics card's rated board power, add about 75 W for the rest of the system, then multiply by 1.2 for a minimum and by 1.4 for comfortable headroom, rounding up to a standard size. A quality ATX 3.1 unit sized this way rides through transient spikes, runs in its efficient middle range and leaves room for an upgrade. The sections below show the math for real 2026 builds and what to look for beyond the wattage number.

PSU wattage math, step by step

1. Processor: use the maximum package power, not the headline TDP. For AMD Ryzen, the package power limit is 1.35 times the TDP: 88 W for 65 W chips, 162 W for 120 W chips and 230 W for 170 W chips. Intel's Core Ultra 7 and 9 K-series chips have a 250 W maximum turbo power, and the Core Ultra 5 245K 159 W.
2. Graphics card: use the board power from the spec sheet: RTX 5090 575 W, RTX 5080 360 W, RTX 5070 Ti 300 W, RTX 5070 250 W, RX 9070 XT 304 W, RX 9070 220 W, RX 9060 XT 16 GB about 160 W. Factory-overclocked partner cards can be rated higher, so check the product page.
3. Everything else: about 75 W covers the motherboard, memory, a couple of SSDs and fans in a typical build. Add more for many fans, lighting, a custom loop pump or power-hungry USB devices.
4. Headroom: multiply the total by 1.2 for a minimum and by 1.4 for comfortable headroom, round each up to a standard size (450, 550, 650, 750, 850, 1000 or 1200 W), and never go below the graphics card maker's recommendation.

These totals are worst cases. In games, the processor rarely runs at its full package power while the graphics card is maxed out, so real draw is usually lower. The margin covers rendering on CPU and GPU at once, transient spikes and future upgrades, and lets the PSU fan stay slow. For reference, NVIDIA recommends 1000 W for RTX 5090 systems, 850 W for the RTX 5080, 750 W for the RTX 5070 Ti and 650 W for the RTX 5070; with a 250 W processor such as the Core Ultra 9 285K next to an RTX 5090, go to 1200 W.

ATX 3.1 and the 12V-2x6 connector

ATX 3.0 and its 2023 update, ATX 3.1, are Intel's current power supply design guides. Two changes matter to buyers.

• Transient handling: the specification requires power supplies to ride through very short power excursions of up to twice their rated power without shutting down. Graphics cards draw brief spikes well above their rated board power, and older units with tight over-current protection could switch off under them.
• Native 16-pin GPU power: ATX 3.1 units provide the 12V-2x6 connector, a revision of the earlier 12VHPWR design with longer power contacts and shorter sense pins, so a plug that is not fully seated is less likely to deliver full power. One cable carries up to 600 W.

An ATX 3.x unit is not strictly required: a good older power supply with enough wattage works with the adapter supplied with the card, as long as each 8-pin input gets its own cable from the PSU. Each 8-pin PCIe connector is rated for 150 W, and the graphics card slot supplies up to 75 W. For a new build in 2026, though, an ATX 3.1 unit with a native cable is the cleanest choice. Push the 16-pin plug in until it latches with no visible gap, and avoid sharp bends right at the connector.

Transient spikes: why some PCs shut down under load

If a PC switches off abruptly when a game starts or a heavy scene loads, with no blue screen and no error, the power supply's protection circuits are a prime suspect. Modern graphics cards change their power draw within microseconds, and the resulting spikes can trip the over-current or over-power protection of a small or aging unit even when the average draw looks fine.

Start with the wattage math above, give each GPU power input its own cable, and reseat the connectors at both ends. If the unit predates ATX 3.0 or runs close to its limit, replacing it with a correctly sized ATX 3.1 model is the reliable fix, and it will usually be quieter too.

80 PLUS and Cybenetics efficiency ratings

Efficiency decides how much power turns into heat inside the unit, not the quality of the power it delivers. At a 400 W load, a 90% efficient unit draws about 444 W from the wall and a 92% efficient one about 435 W, a difference of under 10 W. Platinum and Titanium units pay off mainly in PCs that run under load for many hours a day, such as workstations, AI rigs and home servers, and in small cases where less heat helps. Titanium also requires 90% efficiency at 10% load, and 80 PLUS sets higher thresholds for 230 V mains, where every unit runs slightly more efficiently.

Many recent units also carry Cybenetics ratings from an independent lab that measures efficiency across the whole load range (ETA levels) and fan noise (LAMBDA levels). An efficiency badge says nothing about component quality or protections, so also look at the warranty: premium units often come with 10 years or more.

ATX vs SFX and SFX-L: sizes and fit

High-wattage ATX units are often 160–200 mm deep, so check your case's PSU length limit and leave room for modular cable plugs and any bottom fans. An SFX unit fits ATX cases with an adapter bracket, which many SFX models include. The PC Builder checks the PSU form factor against your case, and our power supply category filters by wattage, efficiency, cabling, ATX version and form factor.

Power supply buying checklist

• Wattage: from the math above, never below the graphics card maker's recommendation.
• Standard: ATX 3.1 with a native 12V-2x6 cable for any card that uses the 16-pin connector.
• Efficiency: 80 PLUS Gold is the sensible default; Platinum or Titanium for long daily loads or small cases.
• Cabling: fully modular for tidy and small builds; semi-modular is fine on a budget.
• Noise: a zero-RPM fan mode keeps the fan off at light loads, where a well-sized unit spends most of its time.
• Protection: pair the PC with a UPS with pure sine wave output, the safe match for modern active-PFC power supplies.
• Cables: replacement and custom cables must be made for your exact PSU series; see cables and adapters and sleeved cables.

Buying a power supply with crypto

A new graphics card is often the reason to replace a power supply, and ordering both together at HodlChip means one payment in Bitcoin, ETH or USDT and free shipping within the EU at $300 or more. Every unit is new and sealed with the full manufacturer warranty, and for the first 12 months we handle any warranty claim with the manufacturer for you. See how to buy PC hardware with Bitcoin for the checkout steps, and the graphics card buying guide for each card's power needs.