How Many Watts Does Your PC Need? A Simple Guide to Choosing a Power Supply

In this guide (8 sections)

• What’s your situation?
• 1. Start with the graphics card maker’s recommendation
• 2. Check typical sizes for common graphics cards
• 3. Work it out yourself
• 4. Leave headroom for power spikes
• 5. Choose quality over a bigger number
• 6. Check the power supply has the right cables
• Real cases: what other users ran into

The right power supplyPSU (power supply): The power supply: the box that takes power from the wall and feeds every part through cables. More in our PC basics glossary →Close ✕ size depends almost entirely on two parts: the graphics card and the processor. Everything else in a PC uses little power. You don’t need an exact number; you need a sensible size with some room to spare, from a good-quality maker.

What’s your situation?

Your situation	What to do	Where to look
You’re only upgrading the graphics card.	Check the card’s recommendation against your current power supply	Steps 1 and 6
You’re building a new PC.	Use the table, then check quality and cables	Steps 2 and 5
You have unusual parts (a top-end processor, several drives or overclocking).	Work it out yourself	Step 3
Your PC turns off in games with your current power supply.	It may be too small, too old or the cables	PC turns off while gaming

1. Start with the graphics card maker’s recommendation

The graphics card uses the most power in a gaming PC, so its maker gives a “recommended system power” or “minimum power supply” figure on the box and product page. It already assumes a typical processor and the rest of the PC.

Tip: the figure for your exact model (for example a factory-overclocked version) can be higher than the basic version’s, so check the page for your exact card.

2. Check typical sizes for common graphics cards

These are the sizes Corsair recommends for a PC with a mid-to-high-end processor (Core i7 or Ryzen 7 class). With a top-end processor, go one size up.

Graphics card	Typical power supply
RTX 4060, RTX 4060 Ti, RX 7600	550 W
RTX 4070, RTX 5070, RX 7700 XT, RX 7800 XT, RX 9070	650 W
RTX 4070 Ti, RTX 4080, RX 7900 XT	750 W
RTX 5070 Ti, RTX 5080, RX 7900 XTX, RX 9070 XT	850 W
RTX 4090, RTX 5090	1000 W

Older or less common cards: check the maker’s page as in step 1.

3. Work it out yourself

If your parts are unusual, add up the main ones using their power drawPower draw (TDP / board power): How much electricity a part uses, in watts. Graphics card makers list it as "board power" or "total graphics power". More in our Power supplies & cables glossary →Close ✕:

1. Graphics card: its “total board power” or “total graphics power” (for example about 200 W for an RTX 4070).
2. Processor: its maximum power (for example about 140 W for a Ryzen 7 7700X under heavy load).
3. Everything else: add about 100 W for the motherboard, RAM, drives and fans.
4. Add about 30% for headroom, then round up to the next common size.

Example: 200 + 140 + 100 = 440 W, plus 30% ≈ 570 W → a 650 W power supply.

Free online calculators (from power supply makers, or the estimate in PCPartPicker’s builder) do the same sum from your exact parts.

4. Leave headroom for power spikes

• Power spikesPower spikes (transients): Very short bursts where a graphics card asks for much more power than normal. They can trip a power supply's protection. More in our Power supplies & cables glossary →Close ✕: modern graphics cards make very short power spikes far above their normal draw. Headroom helps the power supply ride through them instead of switching off.
• Quieter and cooler: a power supply working at half to two-thirds of its rating runs cooler, and its fan stays slower.
• Future upgrades: a bit of spare capacity lets you upgrade the graphics card later without changing the power supply.

A bigger power supply doesn’t waste electricity: the PC only takes what it needs. The only cost is the higher price.

5. Choose quality over a bigger number

A good 750 W unit is better than a poor 1000 W one. Cheap power supplies may not deliver their label’s wattage reliably, or may shut down under spikes.

• Reputable maker and model, with independent reviews.
• Long warranty: 7–12 years usually signals a confident maker.
• ATX 3.0 or newer: designed for modern graphics cards’ spikes, often with a 12V-2x6 cable for new cards.
• The 80 Plus rating80 Plus rating (Bronze, Gold, Platinum): A sticker that says how efficient a power supply is. It isn't a measure of quality or reliability. More in our Power supplies & cables glossary →Close ✕ (Bronze, Gold…) shows efficiency, not quality. Gold is a sensible choice, but it’s not a guarantee.

6. Check the power supply has the right cables

Watts aren’t enough: your power supply must have the plugs your card needs.

• Count the power sockets on the graphics card: two or three 8-pin, or one 16-pin (12VHPWR / 12V-2x6).
• For power-hungry cards, use a separate cable for each socket rather than one cable with two plugs (see why this matters).
• If you need an adapter, use the one that came with the graphics card, and push every plug in fully.

Real cases: what other users ran into

These are real reports from PC forums, summarized in our own words, with a link to each original thread.

Real caseCorsair RM650i · upgrading from RTX 3070 to RTX 4070 TiTurned out to be normalIs 650 W enough for an RTX 4070 Ti?Read what happened

The owner wanted to know whether his 650 W power supply could handle a new RTX 4070 Ti, while NVIDIA recommends 700 W. Replies cited measurements of about 275 W for the card in games, with spikes around 320 W. The owner measured his whole PC at about 500 W at full load and estimated about 570 W with the new card, so he decided his good-quality unit should cope. He mentioned an earlier, worse 700 W unit that kept crashing his PC, which this 650 W one had fixed.

Takeaway: quality and real measurements matter more than the number on the label. See step 5.

Source: Linus Tech Tips Forum

Real caseRyzen 7 3700X · RTX 3070 · be quiet! Straight Power 11 650 WSolution not confirmed by the userShutdowns with an RTX 3070 on a 650 W unitRead what happened

The PC switched off both while gaming and at idle, and a wall meter showed about 710 W just before one shutdown. A reply said a similar PC with a stronger graphics card ran at about 550 W at most on a good 650 W unit, so a healthy 650 W power supply should cope, and suggested the unit itself might be faulty. The thread is marked solved, but the fix isn’t shown.

Takeaway: shutdowns even at idle point to a faulty power supply, not just a small one. See signs your PSU is failing.

Source: Tom's Hardware Forum

Real caseRyzen 7 5800X · RTX 4080 Super · Deepcool 1000 WNot solved by the user1000 W and still switching offRead what happened

After upgrading to an RTX 4080 Super and a new 1000 W power supply, the PC switched off at random, even when launching games. A reply pointed out 1000 W is plenty for this card, and suggested checking every power connection and testing the old graphics card. The owner found all connections fine; after some time away from the PC the shutdowns stopped, with no cause found.

Takeaway: more watts don’t fix everything; check the connections first. See step 6.

Source: Linus Tech Tips Forum

Frequently asked questions

Is a 650 W power supply enough for gaming?

For most mid-range graphics cards (RTX 4070, RTX 5070, RX 7800 XT class), yes, if it’s a good-quality unit. High-end cards need more.

Does a bigger power supply use more electricity?

No. The PC only draws what its parts need. A bigger unit just costs more to buy.

Can I use my old power supply with a new graphics card?

If it has enough watts, the right cables and isn’t very old, yes. If it’s over 7–10 years old or a budget model, a new graphics card is a good time to replace it.

What does 80 Plus Gold mean?

It’s an efficiency rating: less power is wasted as heat. It doesn’t guarantee quality, but most good units are at least Gold.

Do I need an ATX 3.0 power supply?

Not strictly, but it’s recommended for new high-end graphics cards: it’s designed for their power spikes and usually includes the newer 16-pin cable.