Your area rug has seen better days. Between the mysterious black smudge in the corner, general wear and tear over the years, and the random detritus that seem to have fused themselves into your rug’s fibers, you know it’s time for an upgrade. Or perhaps you’ve been gliding along on your wooden floors in slippers for the past decade, always solemnly promising this will be the year you buy that long-postponed living room carpet. And yet, when it comes to selecting rug sizes, the stress of figuring out the right shape and material are enough to make you want to give up your carpet quest before you start.

This year, don’t be that person. “Area rugs play a pivotal role in grounding a space. They provide a great way to define an area, especially when it comes to open layouts. Beyond their practical uses, they also provide a layer of comfort and warmth to a room,” says Isfira Jensen, principal designer and CEO of Nufacet Interiors in New York City, who notes that their aesthetics are also used to complement the surrounding decor with varying textures, patterns, and colors.

Below, Jensen and other interior designers chime in with their tried-and-true rules for selecting the perfect rug sizes for your space, mistakes to avoid when designing around an area rug, and some of our favorite area rugs you can buy online.