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“Where are PSU screws?” is one of those questions that usually pops up at the exact moment you’re ready to mount your power supply and the box is already half-open. The good news: the screws are almost always in predictable places, and the mounting points on the case are easy to confirm once you know what to look for.
This guide focuses on two things: where the screws are physically stored and where the PSU screw holes are on the case. We’ll also cover the screw types you need, what to do if you’re missing the bag, and what to troubleshoot if the screw holes don’t line up.
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What PSU mounting screws are (and why they matter)
PSU mounting screws secure the power supply to the PC case so it can’t shift under cable load or vibration. Most ATX PSUs mount using rear-panel screws through the PSU’s flange into the case’s threaded inserts.
If you use the wrong screw length or thread, you can strip the case threads or damage the PSU housing. That’s why finding both the right screws and the correct mounting holes is the goal.
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Where are PSU screws usually located?
When people ask where PSU screws are, they usually mean either the included mounting screws or the screw holes on the PC. Let’s split it into the places you can physically check first.
In the PSU box or accessory bag
Most PSUs (e.g., Corsair, EVGA, Seasonic, Cooler Master) ship with a small screw bag. It’s commonly tucked into the bottom of the PSU packaging or inside the foam compartment.
Look for a bag with multiple small screws (typically black/standard case screws) and sometimes a zip tie bag. The size is often standard for the case, but don’t assume—check length before forcing.
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In the PC case accessory kit
Many PC cases include their own screw assortment, even if your PSU also includes screws. Check the case accessory box you used for motherboard standoffs, drive rails, and expansion slot covers.
In that kit you’ll usually find multiple lengths and a label or separated compartments. PSU screws are often the ones that match the same black color and diameter as the motherboard mounting screws (but don’t mix them blindly—length matters).
Bag attached to the PSU shroud/cables
Some builders attach the screw bag to cables or to the PSU itself. If you unboxed the PSU quickly, it may be stuck to a cardboard insert or taped near the foam.
Run your fingers along any plastic wrapping seams. It’s an easy spot to miss because the bag can look like clear packaging debris.
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On many cases, screw holes are covered by a blank shroud, or screws may already be loosely installed for shipping/installation. If you see screws near the rear PSU area, don’t remove everything at random—confirm they’re related to PSU mounting.
Try the “rear panel first” approach in the next section to identify which openings are actually for the PSU flange.
Why you might not see screws right away
Common reasons: the screw bag was left in the outer packaging, the screws are inside the case accessory box you didn’t open fully, or the case already has screws pre-installed for a specific configuration.
Also, some PSU shrouds hide access until the PSU is aligned. You might see empty holes but not the threads until you position the unit.
Where are the PSU screw holes on the case?
On most modern ATX mid-tower and full-tower cases, the PSU mounts on the rear bottom or sometimes rear top section of the case. The screw holes are typically clustered near the PSU’s IEC power inlet cutout.
Top/bottom PSU mounting patterns (ATX cases)
- Bottom PSU mount (most common): Screws go into the rear section under the cable management area. The PSU fan faces downward (or upward depending on orientation rules for that case).
- Top PSU mount (some designs): The PSU screws attach near the upper rear panel. This layout often improves airflow and cable routing in certain builds.
- Vertical PSU shrouds (some cases): The mounting points are still near the rear cutout, but access is partly concealed by a shroud panel.
Typical screw quantity and layout
Most ATX PSUs use 4 mounting screws—two on each side of the PSU’s rear flange. Some smaller or non-ATX designs use 2 or a different pattern, but 4 is the common expectation.
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If your case looks like it has only 2 holes, check for 4 total—some holes are partially blocked by metal bends or the PSU shroud.
How to find the exact screw points on your case
If you want certainty, don’t guess. Do a quick visual and alignment check before you start lowering the PSU into place.
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Step-by-step: check the rear panel first
- Place the case on its side so you can see the rear PSU area clearly.
- Find the rectangular cutout where the PSU’s IEC power inlet will sit.
- Look for threaded inserts or screw holes around that cutout.
- Confirm whether you see 2 screw holes on each side of the PSU’s rear flange area (typical = 4).
Step-by-step: verify standoff/metal threading
- Hold the PSU near the opening without pushing it all the way in.
- Visually line up the PSU flange edges with the metal screw points.
- Look for pre-threaded holes in the case. If you can’t see threads, assume they’re there but partially covered by the PSU orientation.
- When aligned, you should be able to start a screw with light finger pressure.
Step-by-step: confirm the PSU orientation
Most PSUs mount so the fan and intake/exhaust airflow direction matches your case design. Commonly, the fan faces down in bottom-mounted layouts (for dust intake policies varies by case).
Practical check: the IEC power inlet should line up with the case rear cutout. If it doesn’t, rotate or flip the PSU before trying to force screws into holes.
Which screws do you actually need?
PSU mounting screws are typically standard PC case screws (steel, black-coated) that match the diameter of the case’s threaded inserts. The most important variables are length and thread compatibility.
Common sizes and thread types
In many ATX builds, PSU mounting screws are commonly the same general type as other case panel screws, often around M3 (metric) with a length frequently in the 4–6 mm range for typical case thickness. However, exact specs vary by manufacturer and case thickness.
Some cases use slightly longer screws if the PSU shroud adds depth. That’s why matching the length you already have (from the case accessory kit) is the safest approach.
If you can’t find the right screws: safe substitutes
- Best substitute: Use the screws from the case accessory kit that look like the correct diameter and match other metal-mounting holes.
- Use finger-start only: If a screw doesn’t start easily by hand within a few turns, stop. Forcing is how you cross-thread.
- Avoid random wood screws: Wrong thread shape will damage the PSU or case inserts.
Tools and prep before you remove/insert a PSU
What you need
- Correct Phillips screwdriver (often #2 is common for PC cases; some PSU screws may take a smaller bit—use the one that fits snugly)
- Anti-static precautions (at minimum, avoid working on carpet and touch grounded metal)
- A flashlight or phone camera for checking screw holes
Power safety checklist
- Shut down the PC.
- Unplug the PSU power cord from the wall.
- If your PSU has a switch, set it to 0 (or off) and press the power button once to discharge remaining power.
- Wait 1–2 minutes before touching internals if you’re unsure.
Installation workflow (so you don’t strip anything)
A PSU is heavy enough that alignment matters. You want screws to start straight, not at an angle.
Mount the PSU to the case
- Position the PSU so the IEC inlet aligns with the case rear cutout.
- Lower the PSU gently into the case opening.
- Start all four screws (or however many your PSU uses) with finger pressure only.
- Once all screws catch the threads, tighten each one gradually in a cross pattern.
- Stop when snug. Over-tightening can strip threads or crack the PSU flange.
Connect cables after the PSU is fixed
After mounting, connect the 24-pin motherboard cable and the CPU power cable(s) (often EPS 8-pin or 4+4). Keep cable routing tidy to avoid fan blade contact.
If you’re troubleshooting later, cable mistakes are more common than screw placement—so verify connectors are fully seated.
Troubleshooting: screws still won’t line up
If the screw holes don’t match, assume alignment or threading mismatch rather than forcing the screw.
Threading mismatch
Symptoms: the screw won’t bite, feels gritty, or starts at an odd angle. Stop immediately and try a different screw length or diameter from the case kit.
Cross-threading can permanently damage the case insert. When in doubt, remove the screw and inspect the first few turns for misalignment marks.
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Case has no rear screw holes
Some compact or unusual cases don’t have the same mounting pattern you expect. Look for hidden holes under a shroud or behind a removable rear panel.
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PSU shroud blocks access
If your case has a PSU shroud, access to the screw points can be tighter. Use a short-handled screwdriver or angle your tool so it contacts the screw head straight.
Try starting screws by fingers while you hold the PSU perfectly aligned.
Screws won’t bite / cross-threading risk
- Back the screw out fully.
- Realign the PSU—often the PSU is 2–3 mm off and the screw isn’t meeting the threaded insert.
- Finger-start again. It should catch quickly.
- If it still won’t catch, stop and confirm you have the correct screw diameter and length.
You’re missing screws and don’t have the bag
If you can’t find the included screws, pull from the case accessory kit first. If that’s empty too, match by diameter and length using the case’s threaded inserts as your reference.
Practical method: measure one existing case screw that threads into a known insert (like a standoff-mounted screw) and use the closest match. When buying replacements, search for the screw size used by your case model rather than guessing.
Common questions about PSU screws
Are PSU screws the same as motherboard standoff screws?
No. Motherboard screws are often shorter and may be a different length or thread type. PSU screws are usually selected to match the PSU flange thickness and case insert depth.
Do all PSUs use 4 screws?
Most ATX PSUs use 4, but not every design follows the same rule. Always count the screw holes on your PSU’s rear mounting flange and match the case openings.
What if I used the wrong screws and tightened too far?
If you feel grinding or the screw won’t back out cleanly, stop. You may have stripped a case insert or damaged the PSU flange. Check for wobble and test-fit a different screw if possible.
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Don’t. A loose PSU can shift, stress cables, and increase vibration. Mount it securely with the correct screws.
Where do I find the PSU mounting manual screw notes?
Your PSU manual sometimes mentions mounting requirements. Your PC case manual is more likely to show the exact mounting screw locations and counts for that chassis.
Bottom Line
PSU screws are most commonly hiding in the PSU’s accessory bag, the case accessory kit, or attached to packaging inserts. The mounting holes are almost always near the rear IEC cutout on the PSU compartment, typically arranged as four points around the PSU flange.
If the screws don’t line up, don’t force them—confirm PSU orientation, start with finger pressure, and verify you’ve got the correct screw diameter and length for your specific case.
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