Whether you're a side or hot sleeper, someone with chronic back pain or the type of person who dozes off as soon as they lay down, the process of finding a new mattress can be anything but dream-like. With the variety of mattress sizes (they range from twin up to a California king) on the market, predetermining the best one for you and your space can, well, keep you up at night. To streamline your decision, we tapped Marissa Murphy-Adriaanse, the Director of Operations and E-Commerce at Pioneer Linens, and mattress experts at Avocado Green Mattress to share their tips and industry tricks.

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Mattresses come in six different sizes: twin, twin XL, full (this is also called double), queen, king, and California king. The size you select depends on your preferences, how many people (pets included!) sleeping on it, and your bedroom. Experts at Avocado advise solo sleepers or small-space dwellers opt for a twin mattress; they're ideal for apartment living, too. But don't confuse a twin with a twin XL, which are five inches longer, but have the same 38-inch width (which makes them better suited for tall solo sleepers).

The next size up is a full. "A full, also called a double, is ideal for individual sleepers with more space or smaller couples who like to sleep close together," shares the Avocado team. Continue up the size ladder and you'll land on the queen, which is the most popular mattress size, share our experts. "It gives individual sleepers lots of space and, for most couples, the right balance of space and intimacy." For those who have a sleep partner, but love their personal space, a king-size mattress is ideal—if you have the room, that is. "A king-size mattress is perfect for couples who like to spread out in their own space, or those that also sleep with a pet or child." Coming in four inches taller and slightly narrower, is the California king; it's great for taller couples who like their space.

Regardless of personal preference, it's most important to choose a mattress that will fit in your bedroom. Before you shop, then, measure the space and compare the results to the dimensions provided by the mattress manufacture. Take your bed frame's numbers into account, too, since sizes aren't always standard. (The Avocado team notes that, luckily, most bed frames take up little real estate, and some even offer nooks and drawers for extra storage.)

After factoring in your room size, your ideal mattress size, and your bed frame's measurements, think about the depth of your mattress in relation to the rest of the room—and calculate the type (and size) of bedding you'll need to outfit your new haven. According to Murphy-Adriaanse, "In an ideal world, you want your mattress to be 14 inches deep," she says, noting that most sheet manufacturers create linens with this number in mind. That means if you choose to splurge on a custom or non-standard size, it will likely cost you on all fronts. "If your mattress isn't 14 inches deep, then your fitted sheets will have to be custom-made to stay on your bed," she affirms, noting that standard width sizes are equally as important.