You're comparing two silk pillowcases. They look identical in the photos, the descriptions read the same, yet one is £35 and the other is £90. The number that usually explains that gap is momme — and it's the one figure many sellers would rather you didn't look at too closely. If you've ever wondered what momme means, or whether a higher number is worth paying for, this guide walks through it properly.
What is momme, exactly?
Momme (pronounced "mummy", abbreviated mm) is a traditional Japanese unit of weight used to describe silk fabric. It tells you how dense the silk is. The higher the momme, the more silk fibre is packed into the same area of cloth — which means a heavier, smoother, more durable fabric.
It works a little like thread count does for cotton, except momme is generally a more honest measure. Thread count can be gamed by counting plies; momme is simply weight, and weight is harder to fake on paper without the fabric giving it away in your hands.
How momme is measured
The definition is oddly specific, and that specificity is the point. One momme equals the weight, in pounds, of a piece of silk measuring 45 inches wide and 100 yards long. So if a length of silk to those dimensions weighs 22 pounds, it's 22 momme silk.
Because the width and length are fixed by the definition, the only variable left is weight. More weight means more silk in the cloth, which means a tighter, denser weave. That's why momme is a reliable shorthand for quality: you can't push the number up without genuinely using more silk.
Momme silk ranges compared
Silk pillowcases on the UK market generally fall between 16 and 25 momme. Here's how the common ranges stack up in practice.
| Momme range | Feel | Durability | Typical price (pillowcase) | Best for |
|---|---|---|---|---|
| 16–19 mm | Light, slightly thin, a touch of translucency | Lower — wears and snags sooner | £20–£40 | Trying silk on a budget; scarves and linings |
| 22 mm | Substantial and smooth, still breathable | High — holds up to nightly use and washing | £50–£75 | Everyday pillowcases (the sweet spot) |
| 25 mm | Heavy, dense, very opaque | Very high, but marginal gains over 22 | £80–£120 | Bedding sets, buyers who want the heaviest option |
Anything below 16 momme tends to feel flimsy and rarely survives regular laundering. It shows up on very cheap listings and is usually a sign to keep scrolling.
Why 22 momme is the sweet spot for pillowcases
A pillowcase has a specific job. It needs to be smooth enough to reduce friction on your hair and skin, durable enough to be washed weekly, and breathable enough that you're not overheating against it all night. That combination is where 22 momme earns its reputation.
At 16–19 momme, you get the smoothness but the fabric is thinner, so it snags and thins out faster — a poor bet on something that goes through the wash constantly. At 25 momme, the silk is denser and more durable, but you pay noticeably more for a difference most sleepers won't feel with their head on a pillow, and the extra weight traps a little more warmth. 22 momme sits in the middle: durable, genuinely smooth, breathable, and sensibly priced. It's the weight most silk specialists quietly agree on for pillowcases, which is exactly why we chose it.
Momme vs grade: don't confuse the two
This trips up a lot of shoppers, because both numbers get thrown around as proof of quality. They measure different things.
- Momme is about the finished fabric — its weight and density. It tells you how much silk is in the cloth.
- Grade (as in Grade 6A) is about the raw fibre — the length, colour and consistency of the individual silk strands before they're woven. 6A is the highest grade of mulberry silk, meaning long, uniform, naturally lustrous fibres with few impurities.
You want both. High momme with low-grade fibre gives you a heavy but rougher, less lustrous cloth. High grade at a low momme gives you lovely fibre in a thin, flimsy fabric. The genuinely good pillowcases pair the two. Our Lunare Home pillowcase is 22 momme AND Grade 6A mulberry silk — the right weight woven from the right fibre.
How to check a seller's momme claim
Some sellers omit momme entirely, list it in the small print, or quietly inflate it. A few practical checks:
- If momme isn't stated at all, treat that as a red flag. A brand confident in its weight will put the number front and centre. Silence usually means it's low.
- Sense-check against price. A "25 momme mulberry silk" pillowcase at £18 is almost certainly not what it claims. Real 22–25 momme mulberry silk costs money to make.
- Look for the fibre type too. "Silk" can mean satin (polyester) or blended silk. You want 100% mulberry silk stated plainly, ideally with a grade.
- Check for independent certification. An OEKO-TEX® Standard 100 certificate confirms the silk has been tested for harmful substances — a sign the seller has had the product independently verified rather than just typing numbers into a listing.
- Trust your hands on arrival. Genuine 22 momme has a real weight and drape to it. If it arrives feeling like a light scarf, the number was optimistic. This is where a proper returns or trial period matters.
Frequently asked questions
Is higher momme always better?
Not for pillowcases. Higher momme means denser, more durable silk, but past 22 momme the gains are marginal for sleep while the price and warmth both climb. For duvet covers or heavier bedding, 25 momme can make sense. For a pillowcase, 22 is the practical peak.
What momme should a silk pillowcase be?
Aim for 22 momme. It's durable enough for weekly washing, smooth enough to benefit your hair and skin, and breathable enough to stay comfortable overnight. Below 19 momme, longevity drops off; above 25, you're paying for weight you won't notice.
Does momme affect how silk feels on skin and hair?
Yes, indirectly. A denser weave at 22 momme gives a smoother, more consistent surface with less friction, which is what helps reduce hair breakage and creasing. Very low momme silk can feel smooth too, but it's thinner and wears rough more quickly.
Is momme the same as thread count?
No. Thread count counts threads per square inch and is used for cotton; momme measures the actual weight of the silk. For silk, momme is the number that matters — thread count isn't a meaningful measure of silk quality.
The short version
Momme tells you how much silk is actually in your silk. For a pillowcase, 22 momme is the weight worth holding out for — durable, smooth and breathable, without the premium of 25. Pair that weight with a high fibre grade and independent certification, and you know what you're paying for.
That's exactly how we built the Lunare Home silk pillowcase: 22 momme, Grade 6A mulberry silk, OEKO-TEX® Standard 100 certified, at £50.99 — where similar pillowcases run £60–£110. It comes with a 30-Night Sleep Trial and free UK delivery over £40, so you can check the weight in your own hands before you commit. Honest spec, sensible price, no optimistic numbers.
