If you’ve treated yourself to the luxury of silk bedding but find your fitted sheet slipping off in the middle of the night, you’re not alone.Silk feels soft, smooth, and elegant, but that also means it needs the right fit to stay in place. So if your mattress is 40cm thick (about 15.7 inches), how deep should your silk fitted sheets be? Let’s break it down.
Step 1: Measure Your Mattress the Right Way
Before buying your sheet, grab a soft tape measure and check your mattress depth.
- Strip the bed — take off all your bedding before you measure.
- Measure from the bottom to the very top seam of your mattress.
- If you use a mattress topper, add that to the total.
- Example: Mattress 40cm + topper 5cm = 45cm total thickness.
- Example: Mattress 40cm + topper 5cm = 45cm total thickness.
Tip: Silk fitted sheets fit best when they’re not stretched too tight, so it’s smart to add 1–2cm of extra space just to be safe.
Step 2: Know What “Pocket Depth” Means
When shopping for fitted sheets, especially silk ones, the key number to look at is the pocket depth — that’s how deep the sheet corners are and how far they wrap around your mattress.
Here’s the simple formula: Ideal pocket depth = mattress thickness + 5–6cm (about 2 inches)
This gives the sheet enough room to tuck under the mattress and stay secure — not too loose, not too tight.
For a 40cm mattress, that means you’ll want a pocket depth of about 45–46cm.
Step 3: Don’t Go Too Big
It might seem safer to buy a deeper sheet, but going too big (like 50cm) can backfire. Silk is slippery by nature, and a sheet that’s too deep will bunch up or slide around. A 44–46cm pocket depth is the sweet spot for a 40cm mattress — snug, smooth, and stays put all night.
Step 4: Pay Attention to Details
Silk is delicate, so small details make a big difference in how your sheet performs.
- Look for a 360° elastic edge. This helps your sheet grip the mattress better.
- Choose high-quality silk. 22–25 momme mulberry silk is ideal — durable, soft, and has a gentle sheen.
- Avoid cheap elastic or poor stitching. They stretch out easily and can cause slipping or tearing.
When your silk sheet fits just right, it hugs the mattress perfectly and brings that soft, luxurious glow to your whole bedroom.
Step 5: Quick Formula Recap
| Mattress Thickness | + Topper | + Extra Allowance | = Ideal Pocket Depth |
| 40cm | (e.g. +0 or +5cm) | +5–6cm | ≈ 44–46cm |
In short, if your mattress is 40cm thick, choose a silk fitted sheet with a pocket depth of 44–46cm.
It will stay smooth, secure, and elegant — no slipping corners or messy folds.
Final Tip: Check the Numbers, Not Just the Words
In the U.S., many silk fitted sheets are labeled “Deep Pocket” or “Extra Deep Pocket,” but every brand measures differently. Always check the actual number before buying.
Best choice: Look for “Deep Pocket 17–18 inch” (about 44–46cm) — that’s the perfect size for a 40cm mattress.
Every morning, you’ll wake up to a perfectly smooth silk surface — no wrinkles, no slipping, just pure comfort and elegance. That’s what true luxury sleep feels like.