The PC Power Supply Calculator is an essential tool for any system builder. It ensures you select a power supply unit (PSU) that can handle the peak power draw of all your components (CPU, GPU, storage, fans, etc.) plus a safety margin for future upgrades and component degradation. Never undersize your PSU!
PC Power Supply Calculator
RECOMMENDED MINIMUM PSU WATTAGE
—Calculated with a 20% safety margin.
Calculation Steps
Click ‘Calculate Recommended PSU’ to see the detailed breakdown.
PC Power Supply Calculator Formula
Safety Margin (W) = Base Load * 0.20
Recommended PSU (W) = Base Load + Safety Margin Formula Source: PCMag (Recommended Safety Margin) Formula Source: Tom’s Hardware (Component Wattage Estimates)
Variables Explained
- CPU Estimated Wattage (W): The Thermal Design Power (TDP) or peak power draw of your Central Processing Unit.
- Graphics Card Estimated Wattage (W): The single largest power consumer in most gaming or workstation PCs. Use its official TDP.
- RAM Sticks Count: The number of memory modules. Each module typically draws 3W-5W.
- Storage Devices Count: Includes all HDDs (higher draw, ~8W) and SSDs (lower draw, ~3W).
- Case Fans / Peripherals Wattage (W): The total consumption of case fans, LED strips, USB peripherals, and liquid cooling pumps.
Related Calculators
- PC Component Compatibility Checker
- CPU Bottleneck Analyzer
- Graphics Card Performance Benchmark
- Cost-of-PC-Ownership Estimator
What is PC Power Supply Calculator?
A PC Power Supply Calculator is a utility designed to help users determine the appropriate wattage for their Power Supply Unit (PSU) based on the individual power requirements of all components installed in their computer. It prevents two major issues: undersizing (which leads to system instability, random shutdowns, and component damage) and oversizing (which leads to unnecessary cost and potentially lower efficiency, as PSUs operate best at 50-60% load).
The calculation typically aggregates the maximum expected power draw of the CPU, GPU, motherboard, RAM, and storage devices. Crucially, a safety margin (usually 15% to 25%) is added to account for power spikes, component aging, and future hardware upgrades, ensuring the system remains stable under stress.
How to Calculate Recommended PSU Wattage (Example)
- Determine Base Component Wattage: Sum the maximum power draw of the primary components. Example: 100W (CPU) + 200W (GPU) + 20W (4 RAM sticks) + 30W (storage/fans) = 350W (Base Load).
- Apply Safety Margin: Calculate the 20% safety margin. Example: 350W * 0.20 = 70W (Safety Margin).
- Calculate Total Requirement: Add the base load and the safety margin. Example: 350W + 70W = 420W.
- Select PSU: Choose a standard PSU wattage slightly above the total required, such as a 450W or 550W unit. It is often recommended to choose a PSU that places the 420W load near the 50-60% efficiency sweet spot.
Frequently Asked Questions (FAQ)
What is the difference between Peak Power and Continuous Power?
PSUs are rated for continuous power. Peak power is a momentary load the PSU can handle, but the continuous rating is the load it can sustain indefinitely. Always use the continuous power requirement from the calculator.
Should I buy a PSU exactly matching the required wattage?
No. You should always select a PSU rated higher than the calculated minimum (e.g., the next standard size: 450W, 550W, 650W, etc.). A PSU is most efficient at around 50-60% load, which saves power and reduces heat.
What is the 80 PLUS certification?
80 PLUS certifications (Bronze, Silver, Gold, Platinum, Titanium) denote the PSU’s energy efficiency. An 80 PLUS Gold PSU, for instance, is guaranteed to be at least 87% efficient at 50% load. Higher efficiency means less wasted heat and lower electricity bills.
Does the type of RAM or storage affect the power draw significantly?
Not significantly, but consistently. DDR5 RAM draws slightly less than DDR4, and M.2 SSDs draw significantly less than mechanical HDDs. However, these are minor contributors compared to the CPU and GPU.