PSU Wattage Calculator

It depends on your parts, mostly the graphics card and processor, which together use the biggest share of the power. Most complete gaming PCs land between 550W and 850W. The quickest way to find your number is to pick your components in the calculator above, which adds up their draw and adds safe headroom for you.

Most gaming PCs need a 550W to 850W power supply, and the exact figure depends on your graphics card and processor. Rather than guess how many watts your gaming PC needs, put your parts into the calculator above and it gives you the recommended power supply wattage with safe headroom. As a rule of thumb, a quality 650W to 750W unit covers most builds.

A typical desktop PC uses about 30 to 70 watts when idle and 100 to 250 watts under load, depending on its parts. Light office machines sit at the low end, while builds with a dedicated graphics card use more. Over an hour of normal use that is roughly 0.1 to 0.25 kWh. Your graphics card and processor drive most of the power draw.

A gaming PC usually draws 50 to 100 watts at idle and 300 to 600 watts while gaming. Mid-range builds land around 350 to 450 watts under load, and the average gaming PC rarely pushes past 500 watts unless it has a high-end graphics card. That running figure is lower than the power supply you should actually buy.

A high-end gaming PC with a card like an RTX 4080 or 4090 can pull 500 to 700 watts or more under a heavy load, and top builds with an RTX 5090 spike higher for short moments. These are the systems that need an 850W to 1200W power supply to stay safe.

A PSU calculator, also called a power supply or PSU wattage calculator, works out how many watts your PC needs. You pick your components and this online PSU calculator adds up their peak power draw, adds safe headroom, and recommends a power supply size. For a gaming PC or any computer build, it saves you from adding up every part by hand to land on the right PSU wattage.

Start with the wattage the calculator recommends, then buy a unit with an 80 PLUS rating from a brand with a good track record. 80 PLUS Bronze is the floor and Gold is a safe pick for most builds. If you have a recent NVIDIA card, look for an ATX 3.0 or 3.1 supply with a native 12V-2x6 connector, which handles power spikes better than an older unit run through an adapter.

80 PLUS Bronze is the sensible minimum. For builds of 650 watts and up, 80 PLUS Gold is the sweet spot for efficiency and quality, and high-end 850W and larger systems benefit from 80 PLUS Gold or Platinum. For the latest NVIDIA cards, look for an ATX 3.0 or 3.1 unit with a native 12V-2x6 connector.

Size the power supply to your parts, not to a round number. Add up the peak draw of your components, add about 30 percent headroom, and round up to a standard size such as 550W, 650W, 750W or 850W. The calculator above does this for you and suggests the right wattage.

500 watts is enough for many mid-range gaming PCs, for example a build with an RTX 4060 or RX 7600. Step up to 650 to 750 watts for cards like an RTX 4070 or 4070 Ti. 350 watts only suits low-power or integrated-graphics builds, while 1000 watts is aimed at high-end cards like the RTX 4090 or 5090. Use the calculator above to match your exact parts.

No. A higher-wattage PSU only delivers the power your components actually draw, so a 1000W unit in a 400W system is not wasteful, just more than you need. The only real downside is cost. A slightly oversized supply runs cooler and quieter, with room to upgrade later.

No. A power supply only pulls the power your components ask for, so a 1000W unit running a 400W system draws about 400W, the same as a 500W unit would. Bigger does not mean thirstier. It just gives you more headroom.

An underpowered PSU tends to cause random restarts or shutdowns when the system is under load, like mid-game. In some cases the PC will not boot at all, or it crashes when the graphics card ramps up. If you see those symptoms after fitting a stronger card, the power supply is a likely cause.

Overclocking raises how much power your CPU or GPU draws, so it pushes your total up. It is worth sizing the PSU with that in mind. The calculator above has an overclocking toggle that adds the extra draw to your estimate, so you can see how much more wattage to plan for.

Free software such as HWiNFO or HWMonitor shows the live power draw of your CPU and GPU, the two biggest users. To see how many watts your whole PC is using at the wall, plug it into a cheap power meter like a Kill A Watt, which includes the power supply's own losses. The software route reports component draw; the wall meter reports total draw.

Check the label on the side of the PSU, which lists its rated wattage along with the model. If your PC is already built and you cannot see the label, look up the exact PSU model from your order or build list. The wattage is also printed on the box the unit came in.

A typical desktop PC without a gaming graphics card uses around 50 to 150 watts in normal use. Office and home desktops average closer to 60 to 100 watts, and modern machines idle in the 30 to 50 watt range. Add a dedicated graphics card and the load figure climbs quickly.

Watts measure power at a single moment, so a gaming PC pulling 400 watts uses 0.4 kWh over an hour of gaming. At an average electricity rate that is only a few cents per hour. Idle use or web browsing costs far less, often under 0.1 kWh per hour.

A single PC case fan uses very little, usually 1 to 3 watts, and a typical 120mm fan draws under 2 watts. Even a full set of case fans plus a CPU cooler adds only around 10 to 20 watts to your total. Fans are a small part of your power budget.

A PC monitor uses roughly 20 to 60 watts depending on size and brightness. A 24-inch 1080p screen sits near 20 to 30 watts, while a large high-refresh or 4K monitor can reach 60 watts or more. A monitor runs off its own plug, so a PSU calculator does not count it.

In sleep or standby a desktop PC uses very little, usually 3 to 6 watts, which keeps memory alive so it can wake quickly. Fully shut down it draws close to zero, apart from a tiny amount to keep the power button and network wake features ready.

Most desktop PCs use the standard ATX size, so a normal ATX power supply fits the majority of towers. Small form factor cases may need a smaller SFX unit instead. Beyond size, check that the PSU has the connectors your motherboard and graphics card need, which modern units almost always do.

A decent power supply usually lasts around 5 to 10 years, and a quality unit can outlive several other parts. Cheap or heavily loaded supplies wear out faster. If a PSU is very old or has been running near its limit for years, it is worth replacing before it takes other parts with it.

Match the UPS to your system's real draw plus the monitor, then add margin for runtime. A gaming PC pulling 400 to 500 watts pairs well with a UPS rated around 800 to 1000 VA, which gives you a few minutes to save your work and shut down safely during an outage.

A modern graphics card can spike well above its rated draw for a fraction of a second. Power supplies also lose a little capacity as they age, and they run most efficiently when they are not maxed out. The headroom covers all of that, which is why the recommended size sits a step above your estimated draw.