Our sleep experts have been testing mattresses, bedding and accessories for years (a few have been testing for up to eight years). At this point, we’ve tested over 300 mattresses from dozens of brands, from bigwigs like Purple and Tempur-Pedic to more niche companies like Sonu and Airweave.

Our team is comprised of bed testers with varying body weights and types, heights, genders and sleep preferences, which helps us provide an overarching assessment of each mattress from a multitude of viewpoints. Many mattresses are tested for long periods, ranging from a month or two up to five years.

We test king-size mattresses just like we would any other bed. When a new mattress arrives at our testing facility, it undergoes rigorous, hands-on testing by each of our experts. We analyze specific characteristics, including firmness, feel, temperature, motion isolation, edge support and other special features the mattress may have.

Firmness

Firmness is rated numerically on a scale of 1 (the softest) to 10 (the firmest), and we use industry terms such as soft or medium-firm to describe it. Our entire team takes turns assessing and ranking the firmness of each mattress, which allows us to make suggestions about which sleeping position and body type it best suits. After subjectively analyzing the firmness, we let our one-of-a-kind Mattress Smasher 9000 do its thing and give us an objective firmness score.

Feel

Another subjective element we review is the feel of a mattress, separate from its firmness. Does it feel springy and responsive when lying on it? Is it easy to switch positions? Or does the dense memory foam conform around our bodies and hold our shape for a while? Does the mattress have a soft, plush pillow top feel, or is it more neutral? Can we feel any coils or zoned support? We do our best to describe exactly what it feels like to lie on each bed to help you determine if it’s right for you without having to test them all yourself.

Read more: Why the Foam in Your Mattress Matters

Temperature

Temperature can be tricky to review when considering each sleeper’s personal preferences and the fact that many mattress brands exaggerate their beds’ cooling capabilities. When testing and reviewing mattresses, we detail how hot or cool the mattress sleeps. Many external factors come into play here (such as climate and environment, bedding, pajamas, etc.), so we test the beds in temperature-controlled rooms without sheets or bedding. Using our extensive knowledge and experience, we analyze its construction and materials and explain how they affect the temperature.

Motion isolation

Motion isolation is a term we use to describe how well the mattress deadens movement across its surface. It’s an especially important feature for light sleepers or those sharing the bed with a partner or pets. We test its motion isolation capabilities by having one expert lie on the bed while another flops around and switches positions. The second method is by setting a glass of water on the edge, rolling toward and away from it to see if the glass tips or falls over.

Edge support

Edge support is typically not as important for king-size mattresses as it is for smaller sizes such as queen or twin. Regardless, testing the edge support allows us to assess how well it holds its structure and support around the perimeter. We sit and lie on the edge to see how the bed responds. Does it cave in and give the sensation that we’ll roll off, or is it sturdy and supportive? We also push down on the edges with our fists to observe how much the edge compresses under pressure.

Special features

Some brands include special features in their mattresses, such as cooling covers for hot sleepers or zoned support for those with back pain. We test and review these additional characteristics and determine which type of sleeper would benefit the most.