| Quick Facts | |
|---|---|
| P-1 max particle size (strip-cut) | 2,000 mm², or 12 mm strip width |
| P-2 max particle size (strip-cut) | 800 mm² |
| P-3 max particle size (cross-cut) | 320 mm² |
| P-4 max particle size (cross-cut) | 160 mm², 6 mm max strip width |
| P-5 max particle size (micro-cut) | 30 mm², 2 mm max strip width |
| P-6 max particle size (micro-cut) | 10 mm², 1 mm max strip width |
| P-7 max particle size (highest security) | under 5 mm², 1 mm max width |
| IRS Federal Tax Information shred spec | 1 mm x 5 mm cross-cut particles or smaller |
| Bonsaii 12-Sheet Micro Cut Shredders particle size (P-4) | about 5 mm x 12 mm |
What is a P-4 security level shredder?
P-4 is DIN 66399's fourth protection class for cross-cut machines, capping particle size at 160 mm² with a strip no wider than 6 mm - the practical floor once a document has a name, account number, or signature on it.
Shopping for a specific model? See our full paper shredder roundup — 10 models compared on the specs that decide it.
That rating comes from DIN 66399, the German standard that assigns every shredder a protection class from P-1 to P-7 based on how large the resulting paper particles can be in square millimeters and how wide a single strip can measure. The standard has since folded into the international ISO/IEC 21964 series, which is why both names show up on spec sheets almost interchangeably today.
At P-4 specifically, the machine has to cut in two directions and keep every piece at or under 160 mm², with no strip wider than 6 mm. Real products land on either side of that ceiling: the Bonsaii 12-Sheet Micro Cut Shredders cuts to roughly 5 mm by 12 mm at P-4, while the Amazon Basics 8-Sheet High Security Micro Cut Paper Shredder produces a marginally coarser 5 mm by 13 mm piece under the same rating. Fellowes builds to that identical spec too - its Powershred 12 Sheet Cross-Cut Paper Home Office Paper Shredder shreds to 5/32 by 1-9/16 inch particles at Security Level P-4, and our Fellowes shredder guide covers that model alongside the rest of its Powershred lineup.
How paper shredder security levels compare, P-1 to P-7
The DIN 66399 ladder runs from P-1, which allows particles up to 2,000 mm², down to P-7, which caps them under 5 mm² and 1 mm wide. Each step up shrinks the maximum particle size and shrinks what anyone could physically piece back together.
P-1 and P-2 are strip-cut territory - long ribbons rather than confetti, with area caps of 2,000 mm² and 800 mm². That's generous enough that a patient person can tape the strips back together, so this tier suits junk mail rather than anything with an account number on it. The woolsche Home Office Paper Shredder is a real example: a 10-sheet strip-cut machine rated P-2 that reduces paper to roughly 6 mm by 297 mm strips.
P-3 and P-4 are cross-cut territory, dropping to 320 mm² and then 160 mm² with a 6 mm strip cap. Most home-office and small-business shredders sit here, and once you group the paper shredder levels this way, the scale stops feeling arbitrary - P-4 is simply where cross-cutting becomes the norm rather than the exception.
P-5 and P-6 belong to micro-cut shredders, capped at 30 mm² and 10 mm², with strip widths down to 2 mm and then 1 mm. The Aurora Commercial Grade 200-Sheet Auto Feed High Security shredder is rated P-5 and cuts to about 2 mm by 12 mm particles - browse our micro-cut shredder guide if that level sounds right for your paperwork. P-7 sits at the top: under 5 mm² and no wider than 1 mm, which matches the exact 1 mm by 5 mm spec the IRS requires for destroying paper containing Federal Tax Information, and the figure NSA/CSS lists as the minimum for shredders that sanitize Top Secret and Sensitive Compartmented Information.
Which paper shredder security level do you actually need?
Match the level to what's on the page: junk mail is fine at P-2 or P-3, anything with a Social Security number or account number needs at least a P-4 rating, and regulated or classified material pushes into P-5 through P-7.
Most households don't need to think past P-2 or P-3 - catalogs and expired coupons aren't worth reconstructing. The moment a Social Security number, bank account, or client's information appears on the page, that changes.
For home offices and small businesses, P-4 tends to be the floor that makes sense here - not because a specific law demands exactly P-4, but because it's the smallest particle size that's still fast enough for daily use. Anyone running through a full banker's box a week is better served by an auto-feed machine, which is what our heavy-duty shredder guide covers. If you'd rather see every option side by side first, our paper shredder buying guide lays out budget, mid-range, and premium picks across every cut type.
Medical practices and law firms tend to step up to P-5 or P-6, even though HHS's HIPAA guidance never names a DIN class - it just requires protected health information be rendered essentially unreadable through shredding, burning, pulping, or pulverizing. Government offices handling classified paper don't get a choice: NSA/CSS requires shredders on its evaluated products list to hit that 1 mm by 5 mm P-7 spec before the machine can sanitize Top Secret material.
P-4 vs P-5: what you actually give up for more security
Stepping from P-4 to P-5 buys smaller, harder-to-reconstruct particles, but it usually costs sheet capacity and run time - most P-5 machines lean on auto-feed hoppers to make up for a much smaller manual-feed pass.
The Fellowes Powershred 12 Sheet Cross-Cut Paper Home Office Paper Shredder, rated P-4, takes 12 sheets in a single manual pass and runs continuously for up to 20 minutes. Compare that to the Aurora Commercial Grade 200-Sheet Auto Feed High Security shredder, rated P-5: its auto-feed tray handles 200 sheets hands-free over a 60-minute run, but the manual slot tops out at just 10 sheets. The Boyuevi 200-Sheet Auto Feed Paper Shredder, also P-5, caps manual feeding even lower, at 7 sheets. Smaller particles take more blade passes to produce, and manufacturers seem to compensate by pushing volume onto automation instead of the manual-feed path.
Noise is where spec sheets get less consistent. The BONSEN Paper Shredder, a 20-sheet P-4 cross-cut model, is rated at 60 dB or quieter; the Boyuevi, a full step up at P-5, lists under 60 dB too. Those numbers read as nearly identical, which says more about how loosely brands round decibel ratings than about any real gap in cutting precision between the two levels. Don't assume a P-5 badge automatically means a louder machine - check the actual number.
What P-4 and higher security levels don't guarantee
A DIN security rating only measures how small the shredded particles are. It says nothing about how the waste is stored afterward, whether the process is third-party certified, or whether the machine handles non-paper media like CDs and old hard drives.
The P-scale is a cut-geometry spec, nothing more. It doesn't cover what happens to shredded paper once it leaves the bin - an unlocked bag by the loading dock, mixing with other recycling, or a broken chain of custody to the recycler. Businesses that need that extra layer typically look at third-party certification like NAID AAA through i-SIGMA, which audits the whole destruction process rather than just the particle size a machine can produce.
No major disposal law names a DIN class either. The FTC's Disposal Rule under FACTA requires businesses using consumer reports to dispose of that information so it 'cannot be read or reconstructed' - shredding, burning, and pulverizing are all listed as acceptable, with no particle-size floor attached. HHS's HIPAA guidance uses nearly identical language for protected health information. Both leave the actual security level to your judgment.
One more limitation worth flagging: the credit-card and CD slot on many home shredders doesn't cut optical media to the same particle size as the paper path, even on a P-4 or P-5 machine. If you're regularly destroying old hard drives or a stack of expired debit cards, treat that as a separate job - a shredder's DIN rating tells you nothing about how it handles media it wasn't primarily built for.