A PSU calculator (also called a power supply calculator, PC power supply calculator, or wattage calculator) adds up the wattage of every part in your build and tells you the right size power supply to buy. The CPU power draw is the single biggest line item, and the TDP data we use to calculate it is the same data in the CPU power reference table further down the page. Pick your CPU and GPU, set RAM and storage, and we add up the per-part draw, apply a 1.3x safety margin, and round up to the next standard PSU size. Powered by TDP data from 55 current CPUs and 54 current GPUs. Use the calculator above, then jump to the PSU tier list at the wattage we recommend.
What is a PSU calculator?
A PSU calculator is a free online tool that estimates the right power supply size for a PC build. You pick the parts in your system (CPU, GPU, RAM, storage, fans) and the calculator adds up the typical sustained draw of each, then applies a safety margin for transient spikes. The output is a recommended PSU wattage you can use as the size filter when shopping for a unit.
Every PSU calculator works the same way. The math is straightforward: CPU TDP plus GPU TGP plus a small baseline for the motherboard, USB, and RGB, plus per-unit draws for RAM and storage. The safety margin (1.2x to 1.5x, we use 1.3x) covers the brief 2x transient spikes modern GPUs pull during load transitions. Without the margin, a PSU that runs at 95% load is loud, hot, and inefficient.
How do we calculate PSU wattage?
Three steps. First, we add the CPU TDP and the GPU TGP. Those are the two biggest draws and the rest is small by comparison. Second, we add fixed baselines for the motherboard, USB headers, RGB, and chipset. Third, we add a per-unit draw for RAM sticks, storage drives, and case fans. The total gets a 1.3x safety margin to cover transient spikes, then rounds up to the next 50W.
Per-part estimates are conservative. RAM draws 5W per DDR5 stick (typical peak, not idle). NVMe SSDs draw 8W each (peak, not average). Fans draw 2W each. Overclocking adds 50W to CPU and 75W to GPU when toggled on. None of these are spec-sheet maxes. They are sustained-load estimates that match what a real build pulls during a gaming or rendering session.
What is the 1.3x safety margin for?
Modern GPUs pull 2x their rated power for a few milliseconds during load transitions, and cheap PSUs trip their over-current protection on those spikes. The 1.3x multiplier covers the spike without forcing you to oversize the unit. A build that draws 500W sustained needs a 650W PSU. That 30% headroom also runs the fan slower (quieter) and keeps the unit in its efficient operating range (90% efficiency at 50% load is the 80+ Gold threshold).
For a 2026 build, the rule of thumb holds. Take your CPU TDP, add your GPU TGP, multiply by 1.3, round up to the next 50W. A Ryzen 7 9800X3D at 120W plus an RTX 5070 Ti at 300W gives 420W times 1.3 = 546W. Round up to 550W. Or for headroom on a flagship GPU, 650W. Either works.
What is a power supply calculator used for?
A power supply calculator (the same thing as a PSU calculator) is used before you buy a new PSU or a new GPU. Two reasons to size your PSU before you buy: matching the right PSU to the build avoids overspending on wattage you do not need, and undersizing trips the PSU’s protection circuit under gaming load. Both are common mistakes. Running a 5070 Ti on a 450W PSU is a real failure mode for the GPU and the PSU.
Most builders also re-run the calculator when they upgrade. Going from a 7700X + 4070 build to a 9800X3D + 5080 build is a wattage jump. The calculator tells you whether your current PSU still fits or if it is time to size up. The same 1.3x safety margin applies.
What is a PC power supply calculator?
A PC power supply calculator is the long form of a PSU calculator, and they are the same tool. PC, power supply, and PSU are three names for the same hardware, the box that converts wall AC to the DC voltages your parts use. The calculator takes the same inputs (CPU, GPU, RAM, storage), runs the same math, and returns the same output (a recommended PSU wattage), regardless of which name brought you here.
The PC power supply calculator is also the right tool when you are upgrading an existing build. Going from a 7700X + 4070 (around 350W sustained) to a 9800X3D + 5080 (around 550W sustained) is a meaningful jump. The calculator tells you whether your current PSU still fits or whether it is time to size up. Most builders re-run it before any GPU swap, and the answer changes about one in three times.
What is a CPU power calculator?
A CPU power calculator estimates how much wattage a specific processor draws under sustained load. The closest official number is the TDP (Thermal Design Power) rating, which every CPU maker publishes in the spec sheet. TDP is the thermal output the stock cooler has to dissipate, and for most modern desktop CPUs the wall draw is within 5 to 10 percent of the TDP figure.
Our PSU calculator uses TDP for every CPU in the dropdown, so the CPU power draw is already in the recommended PSU size. If you just want the CPU draw on its own, the reference table below covers the most popular 2026 desktop processors. The Intel K-series rows are the wrinkle: Intel publishes a 125W base TDP but the chips pull 250W+ at full multi-core load, so we list both. By contrast, the X3D parts are more efficient: cache adds real gaming frame rates but does not push the wattage up, so the AMD X3D rows are closer to the wall measurement than the non-X3D Zen 5 parts.
CPU TDP reference: popular 2026 desktop processors
| CPU | TDP | Notes |
|---|---|---|
| AMD Ryzen 9 9950X | 170W | Zen 5, 16 cores, 32 threads |
| AMD Ryzen 9 9900X | 120W | Zen 5, 12 cores, 24 threads |
| AMD Ryzen 7 9800X3D | 120W | Zen 5 X3D, 8 cores, 16 threads |
| AMD Ryzen 7 9700X | 65W | Zen 5, 8 cores, 16 threads |
| AMD Ryzen 5 9600X | 65W | Zen 5, 6 cores, 12 threads |
| AMD Ryzen 7 7800X3D | 120W | Zen 4 X3D, 8 cores, 16 threads |
| AMD Ryzen 9 7950X3D | 120W | Zen 4 X3D, 16 cores, 32 threads |
| AMD Ryzen 7 7700X | 105W | Zen 4, 8 cores, 16 threads |
| AMD Ryzen 5 7600X | 105W | Zen 4, 6 cores, 12 threads |
| AMD Ryzen 7 5800X3D | 105W | Zen 3 X3D, 8 cores, 16 threads |
| Intel Core Ultra 9 285K | 125W base / 250W max | Arrow Lake, 24 cores |
| Intel Core Ultra 7 265K | 125W base / 250W max | Arrow Lake, 20 cores |
| Intel Core Ultra 5 245K | 125W base / 159W max | Arrow Lake, 14 cores |
| Intel Core i9-14900K | 125W base / 253W max | Raptor Lake, 24 cores |
| Intel Core i7-14700K | 125W base / 253W max | Raptor Lake, 20 cores |
| Intel Core i5-14600K | 125W base / 181W max | Raptor Lake, 14 cores |
The wall-measured max column for Intel K-series is the number to use for the calculator if you plan to push all-core load. Layer the 1.3x safety margin on top of the 253W max to get a 330W CPU contribution, which is the right starting point for an 850W or 1000W PSU on a 14900K + 5090 build.
What if my GPU TGP is not in the database?
About a third of the GPUs in the calculator (mostly older AMD RX 6000 and RX 7000 series) do not have a TGP in our database yet. When you pick one of those cards, a number field appears below the GPU dropdown. Type the manufacturer’s TGP value in watts. You will find it on the card’s spec page or on the TechPowerUp GPU page. The calculation uses whatever you type.
For an ATX 3.x build with a 12VHPWR connector, also check the PSU’s recommended wattage. Some manufacturers (notably Seasonic) publish a minimum PSU size for each GPU on their product page. If the recommended PSU on the manufacturer page is higher than the calculator’s output, use the manufacturer number. The calculator is a starting point, not a substitute for the GPU vendor’s spec.
How do I pick the right PSU tier for my build?
Once the calculator gives you a recommended wattage, jump to the PSU tier list 2026. The list ranks 1,089 current power supplies across 13 letter-grade tiers, with a 4-question finder that scores each unit against your build. The recommended wattage from this calculator pre-fills the wattage filter on the tier list, so you land directly on the units that fit.
For a 550W build, the A+ and A tiers at 550W are the right place to start. For a 1000W workstation, the same tiers at the higher wattage. The D and E tiers are the place to skip. A bad PSU is the most common way to lose other components, so over-spending on the PSU by $20 to $30 is almost always the right call.
Wattage for gaming, workstation, and server builds
Gaming PCs pull 350W to 650W sustained at load, depending on the GPU. A 9070 XT with a 7700X draws about 430W. Pair the same 9070 XT with a 5090 and the number jumps to about 600W. Push a 14900K into the mix with the overclock on and the build pulls 700W+. Use the calculator with the overclock toggle on for the high end. The tier list at the recommended wattage has multiple Tier A picks at every standard size.
Workstations pull more sustained power and run for longer. A 1000W PSU is the right pick for any 8K video editing or 3D rendering build that pulls 700W+ for 8 hours a day. The Platinum and Titanium efficiency tiers start making sense at this workload because the efficiency gain covers the price premium in 2 to 3 years. For a server, the PSU finder Server / 24-7 use case lock the tier to A+ and A only.
For a sense of how the other TechWafer tools line up, the Bottleneck Calculator scores a specific CPU and GPU pair before you buy. The CPU compare hub and the GPU compare hub list every reviewed pair with the recommended PSU wattage. Storage is covered by the SSD tier list. This PSU calculator is the entry point. The tier list is the purchase decision. Both share the same brand philosophy: conservative recommendations, named parts, no fake specs.
Updated 17 August 2026. PSU calculator covers 55 CPUs and 54 GPUs as of the source dataset refresh. Affiliate links via Amazon (tag: techwafercom-20).