"Still Cool sizing, honestly: how the Cool Set and Sleep Dress fit, S to 3XL"
It is 10 p.m., the product page is open, and you are stuck between a medium and a large. You have been here before with other brands. You picked one, it arrived, it was wrong, and the return was enough of a chore that the package sat by the door for two weeks.
So this post is only about Still Cool sizing. No fabric story, no sleep science. Just the numbers, what they mean, how to check them against your own clothes, and what happens if you still get it wrong.
The short answer
Sizes run S to 3XL, which is US 2/4 through 22. The cut is relaxed: it skims, it does not cling, and it is not oversized. If you are between sizes, take the larger. That is what the product pages say, and it is the advice we would give a friend.
The reason for the room is not fashion. Heat leaves your body through your skin, and it needs a little air next to the skin to go anywhere. A cut that hugs you takes that air away. We covered why the shape of a pajama matters as much as its fiber in pajamas for hot sleepers: shorts, a dress or a set. For sizing, the practical result is simple: when in doubt, more room beats less.
Why your usual size is only a starting point
If your size is a medium at one store and a large at the next, you are not imagining it. The United States has no required standard for women's clothing sizes. The Commerce Department did publish one, commercial standard CS 215-58, built on body measurements from a 1939 study. It was always voluntary, was formally declared voluntary in 1970 and was withdrawn entirely in 1983. Since then, every brand has drawn its own chart.
That is why we put the measurements in inches on every product page, and why we keep telling you to compare them with clothes you already own rather than with the letter on a tag. A tape measure and a top you like are more reliable than any size name, including ours.
The Cool Set: the chart, in plain words
The Cool Set is a drop-shoulder short-sleeve tee and full-length flare pants. Here is the full chart from the product page. All numbers are garment measurements in inches, not body measurements.
| Size | US | Top length | Sleeve | Bust | Waist | Hip | Pant length |
|---|---|---|---|---|---|---|---|
| S | 2/4 | 26.4 | 7.0 | 44.1 | 26.0 | 35.0 | 40.2 |
| M | 6/8 | 26.8 | 7.2 | 46.5 | 28.0 | 37.4 | 40.6 |
| L | 10/12 | 27.2 | 7.4 | 48.8 | 29.9 | 39.8 | 40.9 |
| XL | 14/16 | 27.6 | 7.6 | 51.2 | 31.9 | 42.1 | 41.3 |
| 2XL | 18/20 | 28.0 | 7.8 | 55.1 | 35.0 | 46.1 | 41.7 |
| 3XL | 22 | 28.3 | 8.0 | 59.1 | 38.2 | 50.0 | 42.1 |
A few things the table tells you that the size letters do not.
The tee is roomy in the body. The bust measurement is the full way around the garment, and it is generous: that is the drop shoulder and the relaxed cut at work. Do not compare it with your bra size. Compare it with a top you already sleep in, measured the same way (more on that below).
The sleeves are short and get only a little longer. Seven inches at S, eight at 3XL. The drop shoulder means the seam sits down on your upper arm, so the sleeve ends around mid-upper-arm rather than at the elbow.
The pants rely on stretch. The waist and hip numbers are much closer to a body measurement than the tee's bust is. That is because the jersey is 5% spandex and gives, and the leg opens into a flare below the knee. If you are choosing your size by the pants, the hip column is the one to watch.
The pant length barely changes. From S to 3XL, the pants grow by less than two inches. Size is about width, not height. If you are on the shorter side, expect the flare to pool a little at the floor, which many people like in a pajama and some do not. If you are tall, measure a pair of pants you own from the top of the waistband to the hem, and compare that with the pant length column before you order.
The Sleep Dress: the chart, in plain words
The Sleep Dress is a loose short-sleeve dress with a round neck and side pockets. It has the shortest chart of the two, because there is no waist to fit.
| Size | US | Length | Shoulder | Bust |
|---|---|---|---|---|
| S | 2/4 | 34.6 | 22.4 | 43.3 |
| M | 6/8 | 35.2 | 23.6 | 45.7 |
| L | 10/12 | 35.8 | 24.8 | 48.0 |
| XL | 14/16 | 36.4 | 26.4 | 51.2 |
| 2XL | 18/20 | 37.0 | 28.0 | 54.3 |
| 3XL | 22 | 37.6 | 29.5 | 57.5 |
Length is the number that decides how it sleeps. The dress runs from about 35 to 38 inches long depending on size. Where that lands on you depends on your height, not your size. The easy check: stand up, put the end of a tape measure at the top of your shoulder near the neck, and let it hang straight down the front. Wherever 35 or 36 inches falls is roughly where the hem will be. On the model in our photos, it sits above the knee.
The shoulder runs wide on purpose. Like the tee, it is cut so the sleeve drops. That keeps the fabric loose across the upper back, where a fitted nightgown tends to pull when you roll over.
There is no waist to worry about. If you are between sizes on the pants of the Cool Set because of your hips, the dress removes that question entirely. Go by the bust.
How to measure, using clothes you already own
This takes five minutes and is more reliable than measuring your body, because you are comparing a garment with a garment.
- Pick a top you like sleeping in. Something with a fit you would happily repeat, not something tight.
- Lay it flat on a bed or table, smoothed but not stretched.
- Measure straight across the chest, from one armpit seam to the other. Double the number.
- Find the nearest number in the bust column. If yours falls between two sizes, take the larger.
- For the pants, do the same with a pair of soft, stretchy pants you like: across the hip at the widest point, doubled. Then check the length from the top of the waistband to the hem.
If your favorite top measures 47 inches around and you liked it roomy, the large tee (48.8) will feel familiar. If you liked it close, the medium (46.5) will feel a touch looser than you are used to, which is the direction you want for sleep.
If you are still unsure, email hello@stillcoolsleep.com with your measurements and the piece you are looking at. A person reads those and will answer with an actual size, not a link to the chart.
Buying for someone else
Today is Sweetest Day, and gifting season is close behind it, so this comes up. If you are buying for a partner, a sister or your mother, you have two options that work better than guessing.
- Borrow a top from their drawer for five minutes and do the flat measurement above. Put it back folded the same way.
- Choose the dress. With no waist and a forgiving bust, it is the easier of the two to get right without measurements.
If you guess and miss, the return rules below apply to the person who placed the order, so keep the confirmation email.
Care keeps the size
A chart only helps if the garment stays the size it arrived. The care label says machine wash cold and tumble dry low, away from towels and zips, and we mean both halves. Viscose is a fiber that does not like heat: hot washes and high dryer settings are the usual way viscose garments come out smaller than they went in. Cold and low keeps the size you chose. If you want to know more about what viscose made from bamboo does and does not do, read is bamboo viscose cooling?.
If it is wrong
You have 30 days from delivery to send anything back, as long as it is unworn, unwashed and has its tags on. To start a return, reply to your order confirmation or email hello@stillcoolsleep.com. There is no portal and no form to find.
We cannot do direct exchanges yet. If you need a different size, return the first one for a refund and place a new order for the size you want. It is an extra step, and we would rather say so here than have it be a surprise. Shipping is free on every order in the US, and orders ship in 3 to 7 business days.
The short version
S to 3XL, US 2/4 through 22. Relaxed, not oversized. Between sizes, take the larger. The tee gets its room from width, the pants from stretch, and the dress from having no waist at all. Pant length barely changes across sizes, so check it if you are tall. Measure a top you already like rather than trusting the letter on any tag, ours included. Wash cold, dry low. And if it is still wrong, you have 30 days.
For everything else our sleepwear will and will not do, read Still Cool sleepwear: things our pajamas will not do. When you are ready, the full charts are on the Cool Set and the Sleep Dress pages.