PSU Calculator: Power Supply Wattage Calculator

Short answer: most gaming PCs need a 550W to 850W power supply, and the graphics card decides which end you land on. An RTX 5060-class build is comfortable on 550W, an RTX 5070 on 650W, an RTX 5070 Ti on 750W, an RTX 5080 on 850W, and an RTX 5090 on 1000W — NVIDIA’s own published minimums. On the AMD side our estimates are 650W for an RX 9070 or RX 9060 XT and 750W for an RX 9070 XT. Pick your exact parts in the power supply calculator below for a number built from your build rather than a category.

Worked examples

These are this calculator’s own outputs, computed with the same formula the tool runs in your browser — so you can see a real answer without touching a single input.

Mainstream 1440p gaming build — Ryzen 7 7800X3D + RTX 5060 Ti (OC model), 2x DDR5, one Gen3 NVMe, 3 case fans, one AIO, ATX board. (This is the tool’s own default state, so it is the number a visitor sees on page load.)

• Inputs: CPU = Ryzen 7 7800X3D (120W); GPU = RTX 5060 Ti OC (200W peak); DDR5 sticks = 2; Gen5 NVMe = 0; Gen4 NVMe = 0; Gen3 NVMe = 1; SATA SSDs = 0; HDDs = 0; case fans = 3; AIO = 1; USB/misc = 10W; motherboard = ATX (45W)
• Result: Peak draw 409W | Min recommended 550W | Sweet spot 850W. Headline: “Recommended PSU: 850W — your build peaks at 409W. A 850W unit runs your load at 48% utilization, which sits in the 80 Plus efficiency sweet spot (40-50%).”

High-end 4K gaming build — Ryzen 7 9800X3D + RTX 5080 Founders Edition, 2x DDR5, one Gen5 and one Gen4 NVMe, 6 case fans, one AIO, ATX board

• Inputs: CPU = Ryzen 7 9800X3D (120W); GPU = RTX 5080 Founders Edition (360W peak); DDR5 sticks = 2; Gen5 NVMe = 1; Gen4 NVMe = 1; Gen3 NVMe = 0; SATA SSDs = 0; HDDs = 0; case fans = 6; AIO = 1; USB/misc = 10W; motherboard = ATX (45W)
• Result: Peak draw 587W | Min recommended 750W | Sweet spot 1200W. Headline: “Recommended PSU: 1200W — your build peaks at 587W. A 1200W unit runs your load at 49% utilization, which sits in the 80 Plus efficiency sweet spot (40-50%).”

Homelab NAS / Proxmox box — Ryzen 5 5600X on a Micro-ATX board, no dedicated GPU, one NVMe boot drive and six 3.5-inch hard drives, four case fans, air cooler

• Inputs: CPU = Ryzen 5 5600X (65W); GPU = No dedicated GPU / integrated only (0W); DDR5 sticks = 2; Gen5 NVMe = 0; Gen4 NVMe = 0; Gen3 NVMe = 1; SATA SSDs = 0; HDDs = 6; case fans = 4; AIO = 0; USB/misc = 10W; motherboard = mATX (35W)
• Result: Peak draw 206W | Min recommended 550W | Sweet spot 550W. Headline: “Recommended PSU: 550W — your build peaks at 206W. A 550W unit runs your load at 37% utilization.” (no sweet-spot clause)

PSU wattage by graphics card

In a balanced, gaming-first build the graphics card is the single largest draw — roughly 45% of system peak on an entry card and up to about 75% on a flagship — so it is the fastest way to a starting number. Every row below carries its own source, because two different kinds of number appear in this table and the difference matters.

Why the two bases differ. A vendor minimum is deliberately worst-case: NVIDIA’s own note on the RTX 5090 states its 1000W figure is based on a system built around a Ryzen 9 9950X — a flagship CPU, not a mainstream one — so the number carries padding for a processor you may not own. Our estimates are the opposite: the calculator’s itemized minimum for a typical mid-range build, stepped up one retail size. Both are floors. Where a vendor publishes a number, we print the vendor’s, because that is the configuration the card was validated against.

These are minimums, not the calculator’s answer. The tool below targets roughly half load rather than a floor, so its headline recommendation will read higher than this table — on a flagship build, considerably higher. That gap is efficiency and upgrade headroom, not a transient-spike requirement. If you want the smallest defensible unit, use this table; if you want the quietest and most efficient one, use the tool’s number. Note also that 600W is a size few brands actually sell — where a vendor figure lands between retail steps, buy the next size up. For a worked example of how one card’s number changes with the processor beside it, see what PSU an RTX 5070 needs; for how a factory-overclocked board can cost you a whole tier, see what PSU an RTX 5080 needs; and for the one case where our own math lands above the vendor minimum, see what PSU an RTX 5090 needs.

How this power supply calculator works

No vendor’s calculator shows you its math. Here is ours, in full.

1. It sums real component draw, not a flat overhead. Your CPU and GPU peak figures come from the dropdowns; everything else is itemized and added: motherboard (about 45W for ATX, less for Micro-ATX and Mini-ITX, more for EATX), 5W per stick of RAM, 10W per Gen5 M.2 drive, 8W per Gen4, 6W per Gen3, 3W per SATA SSD, 12W per hard drive, 2W per case fan, 12W for an AIO pump and fans, plus whatever you enter in the miscellaneous field (10W by default, for fan controllers, RGB, capture cards, and similar). That total is your peak draw.

2. The minimum is peak plus 20%. The calculator multiplies your peak by 1.2 and rounds up to the next size commonly sold — 550, 650, 750, 850, 1000, 1200, or 1500W; above 1500W it steps in 100W increments, because retail sizes get irregular there. That is the smallest unit it will suggest, and it is a genuine floor: at exactly 1.2x, your peak sits at about 83% of the unit’s rating, which is above the 80% line where the table below starts warning. Treat the minimum as “this will work,” not “this is the one to buy.”

3. The recommended size targets about half load. Power supplies are most efficient, coolest, and quietest loaded near the middle of their range, so the headline recommendation is the size that puts your peak near half the unit’s rating, and the tool flags 40-50% as the sweet spot when your build lands there. It is deliberately larger than the minimum: it buys efficiency, quiet, and room for a future graphics card. It is not a spike requirement — see below.

4. The efficiency table shows every size. Rather than hiding the trade-off, the table rates each retail wattage against your build: above 80% load is under-sized and risks shutdowns, 65-80% works but leaves little upgrade room, and 35-65% is the band worth buying into.

The transient-spike question, answered honestly

Modern graphics cards pull microsecond spikes well above their rated power, and this is where PSU advice usually turns into “buy double.” It should not.

Intel’s ATX 3.0 design guide sets explicit excursion brackets a compliant unit must survive, and they are tiered by duration rather than being one blanket number:

The qualifier matters as much as the number. That 200% bracket applies to units above 450W that ship a native 12VHPWR / 12V-2x6 connector. A smaller unit, or one without that connector, is held to a lower bar — 150% at 100 µs. So “my PSU is ATX 3.x, it handles 200% spikes” is only true for the larger, natively-connectored units.

Where it applies, though, it settles the sizing question: a 750W unit in that class is built to ride out a 1500W spike lasting 100 microseconds. That headroom is already in the standard, so on a qualifying unit you do not buy a bigger PSU to cover transient spikes — you buy a compliant one. On an older ATX 2.x unit paired with a high-wattage card, leave more room, because it was never designed to these brackets.

What ATX 3.1 revised is the connector: the 12V-2x6 design shortens the sense pins so a plug that is not fully seated fails to deliver full power rather than making partial high-resistance contact. We are not going to tell you 3.1 raises or lowers the transient bar relative to 3.0 — we could not retrieve the 3.1 design guide itself, and we do not publish spec claims we have not read. Buy 3.1 for the connector.

One more that vendor calculators skip: if your unit is multi-rail, total wattage is not a single pool. A 1000W multi-rail supply may cap one 12V rail well below the card’s draw, and a high-wattage GPU fed entirely from that rail can trip over-current protection on a supply that is nominally huge. Follow the rail distribution in your PSU’s manual and use separate cables rather than daisy-chaining one pigtail.

Reading the three numbers

Continuous vs. peak vs. transient. A PSU’s headline number is its continuous rating — what it can deliver all day. Your parts list a peak draw, which the calculator sums. Transient spikes are the third number, and the standard above covers them. A unit sized only to the raw continuous total, with no margin at all, can trip its over-current protection under load, which shows up as a random shutdown rather than an error message.

Why the sweet spot is roughly half load. Efficiency curves peak in the middle of a unit’s range, and a supply loafing at half load runs cooler and spins its fan slower — often not at all, on units with a zero-RPM mode. Worth keeping the two measures apart: the calculator’s load percentages are measured against your peak, while the 50-60% figure people quote describes typical sustained draw, which sits below peak. Size so peak stays under about 80% and typical lands near half, and both are satisfied at once.

80 Plus tiers in plain terms. The 80 PLUS badge rates efficiency at fixed load points. At these wattages the bill difference between Gold and Platinum is a dollar or two a month; treat the rating mostly as a signal of build quality, heat, and fan noise. Gold is the floor worth buying for a gaming or always-on homelab box. Our EVGA SuperNOVA 1000 GT review walks through what that looks like in a real unit, and the power & cost calculator turns watts into an annual dollar figure.

A lower-power build is a cheaper build. Undervolting cuts real wattage — around 100W on a high-end card and roughly 50W on a mid-range one, going by the measured results in our own database — which can drop you a PSU size and lower your bill at the same time. The complete GPU undervolting guide covers the method, and our undervolt results database lists measured power savings by card.

If your PC is already shutting down

An undersized or failing supply looks the same from the outside: reboots under load, shutdowns in games, a PC that will not post. PSU failure symptoms covers how to tell a dying unit from an undersized one, and the FAQ below covers testing a supply and finding out which one you already own.

These are conservative component estimates. Real-world idle draw is far lower, and your actual numbers depend on overclocks and the specific models you choose — for a full parts list with compatibility checking, use the PC Builder, and for where each card lands on speed, see the GPU hierarchy.

Sources

• NVIDIA GeForce RTX 50-series official specifications (total graphics power and minimum system power requirement) — RTX 5090, RTX 5080, RTX 5070 family, RTX 5060 family — verified live 2026-07-24; the 5070 and 5060 family pages re-verified 2026-07-25.
• Intel ATX 3.0 / ATX 3.1 desktop power supply design guides — the 200%-of-rated power-excursion requirement for microsecond transients (Intel ATX 3.0 PSU power excursion).
• AMD board power: RX 9060 XT (150W) from the TechFuelHQ PC Builder parts dataset (CC BY 4.0); RX 9070 XT (304W) as cited in our RX 9070 XT undervolt guide; RX 9070 (220W) as cited in our RX 9070 vs RX 9070 XT comparison. The PSU sizes on those three rows are our own estimates, not AMD figures — AMD’s specification pages did not respond when we checked on 2026-07-24.
• Component draw coefficients are this calculator’s own published figures, listed in full in the methodology section above.