Shopping for a duvet can introduce you to a whole lot of terms you’d never heard before, or least terms you’ve forgotten since the last time you went shopping for bedding. Fill, fill power, thread count, and material are four of the biggest factors impacting the quality of a duvet. Before you go out and start comparing duvets, brush up on your terminology.

#1 Fill

The material that fills a duvet will affect how breathable and insulating a duvet is. The three most common duvet fills are down, feathers, and synthetic materials. Synthetic materials are typically the most affordable but the least breathable. Down is highly insulating and might be too much for hot nights unless used in combination with feathers.

#2 Fill Power

As funny as it sounds, fill power is a measure of fluffiness, or the loft of a duvet, and it’s also related to how insulating the down is. It means “down per ounce” and a fill power of 600 or higher is a good sign of a quality duvet.

#3 Thread Count

If you’ve been shopping for duvet covers, you’ve probably heard a lot about thread count. Thread count is based on the number of threads woven into the sheets. Higher numbers are generally associated with higher quality, but that’s not always the case. Since extra “picks” can be woven into the weft (horizontal threads), sometimes thread counts reach into the thousands without really affecting quality. A realistic maximum thread count per square inch is around 500 to 600, though it depends on the manufacturer.

#4 Duvet Cover Material

The duvet cover is a removable cover on your duvet and it plays a big role in how comfortable you feel at night. The most common types of materials are cotton, flannel, silk, polyester, and bamboo.

Cotton may be the most comfortable duvet cover material, especially if you opt for Egyptian cotton. Upland cotton is the most common cotton grown in the world and not as soft as Egyptian or Pima cotton, but it’s an affordable option. Pima cotton has longer threads that are frequently used in bed sheets. It’s grown in the southern United States.

Flannel is related to cotton – it’s cotton that’s been combed and it’s the material you want on your duvet cover on cold winter nights. It traps body heat under the duvet and keeps you warm and cozy.

Silk is a fine fiber produced by silk worms and it’s associated with luxury. However, silk is expensive and while it can feel cool at first, it’s not necessarily the best material for summer.

Bamboo, on the other hand, is breathable like cotton. The one downside is it feels a bit rougher and stiff.

Finally, there’s polyester, the only synthetic material on this list. Typically, you want polyester blended with cotton, as on its own polyester is stiff and rough. Used in a blend, cotton will be more affordable.

It’s time to simplify your duvet shopping. Go online and quickly compare thread counts, materials, and fills. You’ll have a cozy night’s sleep in no time.