These simple, under-$40 T-shirt dresses look chic, but feel like wearing pajamas

If you're looking for a no-frills, airy cotton T-shirt dress, this is it. It comes in seven colors and a range of sizes, including regular, petite and tall lengths. I purchased it in black to wear with sneakers, but I've also tossed it on over a swimsuit to go to the pool while on vacation. 

More than 4,000 Old Navy shoppers give it a glowing five-star review. One wrote: "Love this dress so much, I bought it twice. Perfect T-shirt dress! So cute and fun for the summer."

Related: Keep your cool this summer in 9 airy dresses that won't cling — all under $50

Want a little more length? This maxi is so popular, it's sold out in most colors, but two striped options are still available. It also comes in three lengths, which is super helpful. And because it's made of sturdy cotton, it doesn't lose its shape or cling to your body when it's hot and humid. (I also bought this one in black earlier this year.)

"Love the way this dress falls — so flattering while being super comfy. The fabric is super soft," said a five-star shopper.

This knee-length option is breathable and silky soft, thanks to its Tencel fabric, and it doesn't wrinkle, so it's great for travel. It gets bonus points for having pockets and for coming in petite lengths, which you'll appreciate if you're on the shorter side like me. It comes in black and a gorgeous dark teal.

"Great dress for traveling," said an on-the-go Athleta fan. "This dress is flattering and easy to wear, packs very well, and can be dressed up or down. I love it! Fits true to size."

Related: These flowy travel pants make you look like a 'rich mom,' but feel like pajamas

Here's another maxi for maximum coverage: This one has a scoop neck and a slightly less boxy silhouette than Old Navy's, but it's still flowy and flattering thanks to the stretchy rayon jersey fabric. It also comes in seven colors, all for under $20. 

"This dress is great for summer! On top of being surprisingly flattering, it's also incredibly comfortable!" said one stylish shopper. "The material is super soft but doesn't seem like it will easily fray or snag. It's light and breathable enough to be worn on a humid 88°F day in Northern Illinois, and can be easily styled up with a belt or jacket for a less casual look."

If you already own a simple T-shirt dress and want something with a little more flair, this one has a feminine tiered skirt that will look flattering on everyone. It's extra flowy and breezy, and comes in over 25 colors. (Good luck choosing a favorite!)

"So far, I have the lilac and the red colors," said this repeat buyer. "They are soft, not clingy, and don't draw attention to problem areas like my stomach. Plus, they have pockets! The price is great too. I am going to get one of each color eventually. I get lots of compliments when I wear them."

Loft has a good selection of casual dresses, including this midi T-shirt pick. This one kicks things up a notch with classic stripes and a twisty detail at the waist that gives it a little shape, but keeps it flattering across the tummy. 

"I needed a comfy but cute dress to travel in, and this one is perfect!" said a Loft shopper. "I can dress it up for dinner but can easily throw on sandals or a pair of white sneakers for a casual look."

Cap sleeves and a slub jersey knit make for a cool, laid-back vibe from this Gap Factory fave. Wear it with white sneakers for a baseball game, flip-flops for a hot beach day or a jean jacket once the temps start to drop. It comes in the sophisticated navy shown here, soft green and a vibrant tomato red.

A few shoppers have bought multiples. One wrote: "My new favorite dress! Love the blue color and material. Fits true to size and hits all the curves just the right way. Loved it so much I bought it in black!"