Your PC just crashed mid-game. You’ve updated the drivers, reseated the GPU, and stress-tested the CPU — everything checks out. The real culprit is almost always the power supply, and it’s the last thing most builders think to check.
An undersized PSU doesn’t always fail loudly. It trips its protection circuit during a millisecond power spike — the kind that happens every time your GPU starts rendering a new frame — and your system dies instantly. No warning. No error code. Just a black screen.
This PSU calculator is built to catch that before it happens. Enter your CPU, GPU, RAM, storage, and cooling setup below. We apply real transient spike multipliers from Cybenetics lab data — not just spec-sheet TDP values — and factor in your PSU’s efficiency rating and age. What comes out is a wattage recommendation you can actually trust, along with a confidence score and specific PSU models to buy.
⚡ POWERED BY TECHSEARCHERS
PC Power Supply Calculator
Enter your components below and get an exact PSU wattage recommendation — with spike analysis, efficiency modelling, confidence score, and products to buy. Takes under 60 seconds.
Not sure which PSU to buy? Select your components above and click Calculate — we’ll tell you exactly which power supply your build needs.
850W
Recommended PSU
Safe
Confidence
90%
Base 0W Spike 0W PSU 0W
0W
Base draw
0W
Peak spike
0%
Headroom
0%
Confidence
🔍 Why this PSU size?
Component base draw0W
Peak transient spike0W
Efficiency loss at wall+0W
Capacitor aging penalty+0W
25% safety headroom+0W
Future upgrade buffer+0W
Recommended PSU 0W
📐 How we calculate power
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TDP is not your real power draw
TDP (Thermal Design Power) is a heat rating — not a watt meter. Your GPU’s actual peak can briefly hit 180% of TDP during gaming. That gap is what kills underpowered systems.
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We use lab-tested spike data, not guesses
CPU: 1.2x TDP · GPU: 1.35x TDP. Per-card values from Cybenetics PSU lab and HWiNFO GPU power analysis.
🔥
Overclocking adds more draw
No OC applied. Toggle OC above to add headroom for your overclocked CPU or GPU.
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Efficiency rating and PSU age both matter
At 87% efficiency, your components need 500W but your outlet supplies 575W — the rest is heat. Older PSUs also lose capacity as their capacitors degrade. Aging adds 0% extra draw over time.
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A 25% safety buffer is built in
PSUs run best between 40–80% of their rated load. We add 25% headroom above your calculated wall draw so your PSU stays in that sweet spot — even during heavy gaming or rendering sessions.
🛒 Recommended PSUs — Amazon
Data: Cybenetics PSU lab · HWiNFO GPU power analysis · TechPowerUp GPU DB. Affiliate disclosure: links may earn a commission at no extra cost to you. Verify prices before purchase.
💡 PSU Buying Tips Worth Knowing
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Always choose 80+ Gold or higher
Bronze wastes power as heat. Gold (87%) and Platinum (92%) save on electricity and run cooler. Gold is the minimum we recommend for any build over 400W.
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Go fully modular if you can
Only connect the cables you need. Fewer cables means better airflow, a cleaner build, and easier upgrades. Worth the small price premium on mid-range and above.
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GPU spikes are the #1 crash cause
High-end GPUs briefly draw 1.3–1.5× their rated TDP per frame. A PSU without enough headroom cuts power instantly — and gets blamed on drivers or heat.
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Never daisy-chain GPU power cables
Each PCIe connector needs its own separate cable run from the PSU. Daisy-chaining runs too much current through one wire — a fire risk, not just instability.
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Replace your PSU every 5–7 years
Capacitors degrade silently. An old PSU near its rated load delivers unstable power — and when it fails, it can take your GPU or motherboard with it.
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Stick to proven PSU brands
Best options based on lab testing: Seasonic, Corsair HX / RM, be quiet!, EVGA SuperNOVA, Fractal Ion. Your PSU protects every other part — don’t cut corners here.
About this calculator
Most PSU calculators add up spec-sheet numbers and add a flat buffer. This one goes further. We apply lab-measured transient spike multipliers from Cybenetics PSU testing (1.35× on GPU, 1.2× on CPU), calculate real wall power based on your 80+ efficiency tier, and add a wear factor for older PSUs whose capacitors have degraded over time. The 25% safety headroom on top of all that keeps your PSU running in its efficient 40–80% load zone — not struggling near its ceiling.
GPU data is sourced from TechPowerUp’s GPU database and HWiNFO power measurements. CPU draw uses manufacturer TDP adjusted by the Cybenetics spike multiplier. Unlike tools that push higher wattage for sales, the wattage recommendation is calculated purely from your component data — product matches come after, never before.
Your results show base draw, peak spike, efficiency loss, aging penalty, and safety buffer as separate line items — nothing is hidden. Every watt is explained so you know exactly why that PSU size was recommended.
Important: All results are estimates based on typical measured consumption. Actual draw varies by hardware revision, BIOS power limits, cooling setup, and workload. For professional workstations or mission-critical builds, verify peak draw with HWiNFO under a real production load before buying.
Affiliate note: Product links may earn a small commission at no extra cost to you. The recommendation is never influenced by which products are available. Always verify prices before purchasing.
Frequently asked questions
What is a PSU and why does wattage matter for my PC?
A PSU (Power Supply Unit) converts power from your wall outlet into the stable voltages your PC components need. If the wattage is too low, your system crashes, refuses to boot, or damages components over time. Too high and you waste money on an oversized unit running inefficiently. Getting the wattage right keeps your build stable, safe, and efficient.
How does this PSU calculator work?
You select your CPU, GPU, RAM, storage, cooling, and PSU preferences. The calculator combines your components' real power draw with lab-measured transient spike data from Cybenetics (1.35× on GPU, 1.2× on CPU), adds your efficiency tier loss and capacitor aging factor, then applies a 25% safety buffer. The result is the minimum safe PSU wattage for your exact build — not just a rough estimate.
What is a transient spike and why does it crash my PC?
Every time your GPU starts rendering a new frame, it demands a short power burst far above its rated TDP — lasting only milliseconds but enough to trip your PSU's protection circuit. When that happens, your system cuts power instantly with no warning or error message. This is the #1 cause of random gaming shutdowns that get misdiagnosed as driver problems or overheating.
Why does my result here differ from other PSU calculators?
Most calculators use spec-sheet TDP numbers which are heat ratings — not real power measurements. This tool applies per-component spike multipliers measured in Cybenetics PSU lab conditions, calculates actual wall power based on your 80+ efficiency tier, and adds a capacitor wear factor for older units. The result accounts for peak millisecond spikes — which is what actually causes instability — not just average sustained load.
What does the confidence score mean?
It shows how precisely your recommendation is based on real measured data. Selecting your exact CPU and GPU models gives 90%+ confidence because we have specific lab data for those components. Leaving fields unspecified or enabling overclock toggles with unknown power limits lowers the score — but the calculator automatically widens the safety buffer to compensate. A lower score means more margin built in, not a wrong answer.
Should I buy exactly the wattage the calculator recommends?
The recommendation already includes a 25% safety buffer so it is conservatively sized. If you plan to upgrade your GPU within the next 12–18 months, use the future upgrade buffer option to size up one tier. Do not go more than one tier above without a reason — PSUs are least efficient at very low loads and you waste money running a 1000W PSU on a 300W system.
Can I use this calculator to check if my existing PSU is causing crashes?
Yes — this is one of the most common uses. Select all your current components, set the PSU age slider to match how old your unit is, and compare the recommended wattage against your PSU's rated wattage. If your PSU falls below the recommendation, it is a likely cause of any instability you are experiencing. If it is within range but over five years old, consider replacing it anyway — capacitor degradation is invisible until it fails.
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