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Learn the differences between flat sheets vs fitted sheets
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Couple making the bed with the sheet ready to be installed


Learn the differences between flat sheets vs fitted sheets

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You might be wondering, should you use a fitted sheet or a flat sheet? 

Many people use both on their beds. 

Still, the flat sheet vs fitted sheet debate is ongoing and individuals can't seem to agree. If you're not sure yourself, perhaps this guide by Polysleep, your mattress specialist, will help.

What are flat sheets and fitted sheets?

Flat bed sheets are large pieces of fabric you spread over your mattress to rest on its surface.

They don't have the elastic on them to fit over the mattress corners (like fitted sheets). Instead, they have only a stitched seam around the edges to keep the material from unraveling with use. 

On the other hand, fitted bed sheets are also big pieces of fabric, but they're made to snugly fit over your mattress.

They won't come off your mattress while you're sleeping because of the elastic band sewn into the material's seam. This elastic helps the sheet hug the mattress's corners, so while you're moving around in your sleep, the sheet stays put.

Flat sheets vs fitted sheets: how and why to use them?

Flat bed sheet

Man smoothing out the flat sheet with the iron

Flat bed sheets, also referred to as top sheets, are placed on top of the fitted sheet, but under blankets and duvets.

They're used to make your bed more inviting and to keep your blankets and duvet covers from becoming dirty. This is because you typically wash your sheets more regularly than your blankets or duvet cover.

Reasons to use them are:

  • Protects blankets and duvets
  • Works like a barrier against skin irritants and ailments
  • Helps keep a comfortable temperature

Fitted sheet

A couple placing the fitted sheet on their mattress

Fitted sheets, also referred to as bottom sheets, cover and protect your mattress. These are the ones you actually lie directly on top of. You can use a mattress protector underneath.

Reasons to use them are:

  • Can be easily removed or changed
  • Protects your mattress
  • Closely fits to provide a smooth sleep surface

Flat Sheet vs Fitted Sheet: Specifications

There are different specifications for both.

Fitted sheets offer:

They provide protection for your mattress from regular wear and tear. This can come in the form of:

  • Rips
  • Tears
  • Liquids
  • Food
  • Bodily fluids

Mattresses are the costliest part of your bed and can last you between 10 to 12 years (sometimes 20, depending on the mattress) if you take care of them properly.

When your fitted sheet fits properly on your mattress, it shouldn't be easily dislodged from either corner, but rather fit snugly with no wrinkles. 

Using the proper measurements, you should be able to pull the sheet over each mattress corner snugly to create a smooth, but flat sleep surface.

Fitted sheets may fit snugly around your mattress, but it only takes a simple pluck of one corner to release its hold and easily remove the sheet. 

Being easy to remove is ideal when it’s time to wash your sheets. It's much easier than trying to take off a quilted mattress cover, which is bulky and difficult to remove, particularly when covering the whole mattress. 

You can typically launder your fitted sheets right at home, so you don't have to worry about any costly dry cleaner trips to clean them. Instead, you just follow simple cleaning instructions.

Flat sheets offer:

Flat sheets are supposed to rest right underneath your bed's blanket or comforter. They are also supposed to cover your body while you sleep. It provides your fitted sheet protection from rips or stains. 

Flat sheets can also provide protection for your primary bed covering, regardless of whether it's a duvet, blanket, or comforter

Flat sheets can work as a barrier for your skin against different irritants like:

  • Bacteria
  • Mites
  • Dust
  • Parasites

These critters can actually live up to five years in your mattress's dark corners. 

Some irritants can affect your skin to where it's covered in a rash and itchy or maybe even threaten your respiratory system. 

If you're suffering from common skin issues like psoriasis or eczema, flat sheets crafted from soothing materials like linen, cotton or silk could help cool your skin because of their natural moisture-repellent properties.

Flat sheets can provide sleepers with the benefit of temperature control. 

Using flat sheets during the summer can help the body adjust naturally its core temperature to a cooler temperature. 

They could also protect you from irritants on hot or humid nights, depending on the climate you live in. 

With specific materials that naturally repel moisture, flat sheets not only add comforting and warming layers to your bed, but they could also protect your sensitive skin from direct contact with a comforter or heavier blanket.

Tips to Choose the Right One

A clean bed with a good sheet


Materials are a matter of personal preference. While synthetic materials like polyester are cheaper, natural materials such as 100% cotton are breathable, softer for your skin, and easy to care for and wash.

Thread Count

A decent thread count is about 200 to 800. Anything over 800 may feel nice still, but for most individuals, increasing the thread count doesn't usually translate into an increase in quality. 

Anything under 200, however, doesn't feel as nice to sleep on. Even worse, these sheets only last a few cycles in the wash before they begin tearing and pulling.


Nothing feels as good as getting into bed on clean sheets (flat or fitted). There's just something about a clean sheet's crisp, cool feeling.

So, regardless of the type of sheet, you'll want to care for it properly.

  • Don't overcrowd the sheets in the wash with other laundry or towels. Make sure they have enough room to move around freely in the washer and dryer to help preserve their feel and quality.
  • Wash the sheets in cool water (warm is okay) with mild detergents. Cold water will help retain the sheet's color and shape.
  • Use a medium setting when drying your sheets. 
  • Promptly remove your sheets from the dryer and fold them, so they won't wrinkle. Letting them sit in the dryer will just cause a wrinkled mess. If you do need to refresh them, run them on a short cycle with a damp towel.


Sheets might shrink over time in the dryer. So, you might think fitted sheets are best, and they can be. You'll just want to measure your mattress to ensure you're getting the right size sheet.


With fitted sheets, it's essential you choose the proper size to match your bed exactly. The fitted corners won't properly work on the wrong size mattress. 

You'll also want to consider your mattress's depth (height) and whether you're using a mattress topper. Usually, you can rely on a standard fitted sheet to fit a mattress up to about 12 inches deep. Typically, deep pocket bed sheets will usually fit mattresses of up to 17 inches in depths. The pocket of most high-quality sheet styles will generally be greater than 15 inches deep.

With flat sheets, it's a bit more relaxed when it comes to size.


There are affordable options for both flat and fitted sheets.

What size of flat sheet and fitted sheet for your Polysleep and Zephyr mattresses?

Learn more : The Bed Sheets Size Guide

The size measurement of a bed sheet

The Polysleep measurements and dimensions:

The Polysleep Mattress  Dimensions
Twin 39” x 75” x 11.5”
Twin XL 39” x 80” x 11.5”
Full 54” x 75” x 11.5”
Queen 60” x 80” x 11.5”
King 72” x 84” x 11.5”
Cal King 72” x 84” x 10”

The Zephyr measurements and dimensions:

The Zephyr Mattress Dimensions
Twin 39” x 75” x 11.5”
Twin XL 39” x 80” x 11.5”
Full 54” x 75” x 11.5”
Queen 60” x 80” x 11.5”
King 72” x 84” x 11.5”

Flat Sheet Size Guide: The Polysleep and The Zephyr Mattresses

Mattress Size Flat Sheet Size: (approximate)
Twin 66” x 96”, 168 x 244 cm
Twin XL 66” x 96”, 168 x 244 cm
Full 96” x 102”, 243 × 259 cm
Queen 96” x 102”, 244 × 259 cm
King 102” x 112”, 259 × 284 cm
Cal King 102” x 108”, 259 × 274 cm

Fitted Sheet Size Guide: The Polysleep and The Zephyr Mattresses

Mattress Size Fitted Sheet Size: (approximate)
Twin 39” x 75” or 96 × 190 cm
Twin XL 39” x 80” or 99 × 203 cm
Full 54” x 75”, 137 × 190.5 cm
Queen 60” x 80”, 153 × 203 cm
King 76” x 80” or 193 × 203 cm
Cal King 72” x 84”, 183 cm x 213

Please note that the Polysleep and Zephyr mattresses have a depth (height) of 10 inches and 11.5 inches, respectively. The sizes above should allow sufficient material for both fitted and flat sheets to be a good fit.

Also discover our mattress topper!

Polysleep folded round mattress topper

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