Use this tool to estimate the total power consumption of your planned PC build and find the recommended wattage for your Power Supply Unit (PSU). Getting the right PSU ensures stability, efficiency, and longevity for your computer components.
PC Power Calculator
Recommended PSU Wattage
This includes a 25% safety buffer for peak loads.
PC Power Calculator Formula
The calculation estimates the maximum possible power draw and applies a safety margin.
Total Estimated Load (TEL):
$$ \text{TEL} = (\text{CPU} + \text{GPU}) + (\text{RAM sticks} \times 5W) + (\text{Storage drives} \times 10W) + \text{Overhead} $$Recommended PSU Wattage (RPW):
$$ \text{RPW} = \text{TEL} \times 1.25 $$Formula Sources: Tom’s Hardware PSU Guide, PC Gamer Build Guide
Variables Explained
The power consumption figures used in this calculator are:
- CPU Wattage: The Thermal Design Power (TDP) rating of your processor, found on the manufacturer’s specification page.
- GPU Wattage: The graphics card’s maximum power draw, which is typically the single largest component load.
- RAM Sticks: Each DDR4/DDR5 stick is approximated to use 5W of power under load.
- Storage Drives: Each HDD or high-performance SSD is approximated to use 10W of power.
- Overhead: A fixed wattage (default 50W) to cover motherboard, fans, liquid cooling pumps, and USB peripherals.
Related Calculators
- PC Bottleneck Checker
- Monitor Resolution DPI Calculator
- Frame Rate (FPS) Calculator
- Hard Drive Storage Converter
What is PSU Wattage Calculation?
Calculating the correct Power Supply Unit (PSU) wattage is the most critical step in building a stable computer. The PSU provides the necessary electrical power to all components. An undersized PSU can lead to system instability, random shutdowns, and potential damage to components, especially under heavy load (like gaming or rendering).
The calculator’s primary goal is to determine the Total Estimated Load (TEL) of all parts operating simultaneously, and then apply a safety buffer. This buffer, typically 20% to 30%, is crucial for handling power spikes (transient loads) and ensuring the PSU operates at peak efficiency (usually around 50% of its maximum capacity) for longevity and lower heat generation.
How to Calculate PC Power (Example)
- Identify Component TDPs: A builder selects a CPU with 125W TDP and a GPU with 350W TDP.
- Calculate Auxiliary Power: The builder plans for 2 RAM sticks (2 x 5W = 10W) and 2 SSDs (2 x 10W = 20W). The fixed overhead is 50W.
- Determine Total Estimated Load (TEL): $125W (\text{CPU}) + 350W (\text{GPU}) + 10W (\text{RAM}) + 20W (\text{Storage}) + 50W (\text{Overhead}) = 555W$.
- Apply Safety Buffer (25%): $555W \times 1.25 = 693.75W$.
- Select PSU: The builder should choose a PSU rated at or above 700W (e.g., 750W) for optimal performance and safety.
Frequently Asked Questions (FAQ)
Why do I need a safety buffer in my PSU calculation?
A safety buffer (usually 20-30%) is essential for handling power spikes that occur during component initialization or sudden shifts from idle to heavy load. It also allows the PSU to run at its most efficient range (typically 40-60% load), which reduces heat and extends the unit’s lifespan.
What happens if my PSU wattage is too low?
An undersized PSU will likely cause system instability, random reboots, and crashes when components draw peak power. In extreme cases, it could potentially be damaged due to overloading.
Is 80+ Gold efficiency included in the wattage calculation?
The efficiency rating (like 80+ Gold) affects the power drawn from the wall outlet, but not the power delivered to the components. The calculation determines the maximum *output* required by the PC. However, having a high-efficiency PSU is always recommended for reducing wasted heat and electricity consumption.
How often should I recalculate my required PSU wattage?
You should recalculate whenever you plan to upgrade a major component, particularly the CPU or the GPU, as these are the components responsible for the vast majority of the system’s power draw.