PSU Calculator

About PSU Calculator

A power supply that is too small causes crashes under load. One that is too large wastes money. This PSU calculator adds up the power draw of every component in your build - CPU, GPU, RAM, storage drives, and fans - then recommends a standard PSU wattage with 20% headroom for power spikes and future upgrades.

How the Wattage Estimate Works

Each component adds its TDP (thermal design power) or typical power consumption to a running total. A 50W baseline covers motherboard, chipset, and VRM overhead. The calculator then multiplies by 1.2 for headroom and rounds up to the nearest standard PSU size.

Component	Typical Power Range	What Affects It
CPU	65-253W	Core count, clock speed, architecture. Intel 14th Gen K-series up to 253W, AMD Ryzen 9000 series 65-170W
GPU	75-600W	GPU tier and generation. RTX 4060 at 115W, RTX 4090 at 450W, RTX 5090 at 575W
RAM	3-10W per stick	DDR4 about 3-5W per DIMM, DDR5 about 4-8W per DIMM
SATA SSD	2-5W	Read/write activity level
NVMe SSD	5-12W	PCIe Gen 4/5, active read/write can spike higher
HDD	6-12W	Spin speed (5400 vs 7200 RPM), 3.5" vs 2.5"
Case fans	1-5W each	Size, RGB lighting, speed
AIO pump	5-15W	Pump speed and model
Motherboard + chipset	30-80W	Higher for enthusiast boards with many features

Why 20% Headroom Matters

Modern GPUs draw power in sharp transient spikes that can exceed the rated TDP by 50% or more for fractions of a second. NVIDIA calls these "transient power excursions." If the PSU cannot handle these spikes, the system triggers an overcurrent protection shutdown - the PC simply turns off during a game or benchmark. The 20% recommendation accounts for these spikes and gives room for future upgrades.

GPU	Rated TDP	Measured Transient Spikes	Recommended Minimum PSU (with CPU)
RTX 4060	115W	Up to 170W	550W
RTX 4070 Ti	285W	Up to 350W	700W
RTX 4080	320W	Up to 420W	750W
RTX 4090	450W	Up to 600W	850-1000W
RX 7800 XT	263W	Up to 310W	650W
RX 7900 XTX	355W	Up to 430W	800W

Standard PSU Sizes

Power supplies come in standard wattage steps. The calculator rounds up to the nearest one:

Wattage	Typical Build	Price Range (80+ Gold)
450W	Office PC, HTPC, no dedicated GPU	$40-60
550W	Budget gaming (RTX 4060, RX 7600)	$50-80
650W	Mid-range gaming (RTX 4070, RX 7800 XT)	$60-100
750W	High-performance gaming (RTX 4070 Ti, RX 7900 XT)	$80-120
850W	High-end gaming (RTX 4080, overclocked builds)	$100-150
1000W	Enthusiast (RTX 4090, dual GPU workstations)	$130-200
1200W	Extreme builds, heavy overclocking	$180-280
1600W	Multi-GPU, server-class workloads	$300-500

80 Plus Efficiency Ratings

The 80 Plus certification tells you how efficiently the PSU converts AC wall power to DC power for your components. Higher efficiency means less wasted electricity and less heat.

Rating	Efficiency at 20% Load	Efficiency at 50% Load	Efficiency at 100% Load	Best For
80 Plus (White)	80%	80%	80%	Budget builds where cost is the priority
80 Plus Bronze	82%	85%	82%	Budget to mid-range gaming PCs
80 Plus Gold	87%	90%	87%	Most gaming and workstation builds (best value)
80 Plus Platinum	90%	92%	89%	Enthusiast builds, systems running 24/7
80 Plus Titanium	92%	94%	90%	Servers, workstations with high electricity costs

Gold is the sweet spot for most builders. The jump from Bronze to Gold saves meaningful energy over a year. The jump from Gold to Platinum saves less while costing significantly more. For a look at electricity costs over time, check the electricity cost calculator.

Modular vs Non-Modular

Type	How It Works	Pros	Cons
Non-modular	All cables permanently attached	Cheapest option	Unused cables clutter the case, harder to manage airflow
Semi-modular	Main cables (24-pin, CPU) attached; others detachable	Good balance of price and tidiness	Still has some fixed cables you might not use
Fully modular	All cables detachable	Cleanest builds, only use what you need, easier to upgrade cables	Costs more, cables are not interchangeable between brands

Important: never mix modular cables between different PSU brands or even different models from the same brand. The pin layouts can differ, and using the wrong cable can destroy components.

ATX 3.0 and the 12VHPWR Connector

NVIDIA RTX 4000 and 5000 series GPUs use the 12VHPWR (or 12V-2x6) connector, which can deliver up to 600W through a single cable. ATX 3.0 PSUs include this connector natively. Older PSUs require an adapter from two or three 8-pin PCIe connectors, which works but adds bulk. If you are building new with a high-end GPU, an ATX 3.0 PSU simplifies cable management.

Common PSU Mistakes

Mistake	Why It Happens	What to Do Instead
Buying the cheapest no-name PSU	Looks like a good deal	Stick to reputable brands with proper certification and protections
Sizing for exactly the calculated wattage	Trying to save money	Always add 20%+ headroom for spikes and upgrades
Reusing old PSU cables with a new PSU	Cables look identical	Always use the cables that came with your specific PSU model
Ignoring the 12V rail amperage	Only looking at total wattage	Check the 12V rail capacity - it powers the CPU and GPU
Daisy-chaining PCIe power cables	Using one cable for two GPU connectors	Use separate cables for each GPU power connector when possible

To check whether your CPU and GPU are a balanced pairing, the bottleneck calculator compares tiers at different resolutions. For overclocking power estimates, the overclocking calculator shows how voltage and frequency affect power draw. All calculations run in your browser with no data sent anywhere.