Bamboo Muslin Lightweight Baby Sleep Sack 0.5 TOG - Mini Mathletes
Numbers, plus signs, and a small mathematician who hasn't met long division yet.
0.5 TOG. The warm-weather sleep bag. Built for nursery temperatures between 75 and 81°F — summer nights, top-floor bedrooms, homes that don't run central AC. The weight you reach for at 11 p.m. on a sweaty August night when a 1.0 TOG has your baby sweating through the back.
Material. Tanboocel viscose from bamboo and cotton, woven into an open-weave muslin. Two notes on the fiber. Tanboocel is a branded viscose-from-bamboo fiber produced through a closed-loop process that's a step beyond generic bamboo viscose — third-party verified, lower water and chemical footprint. We use it only on our 0.5 TOG muslin pieces, our swaddles, and our crib sheets. It is not the same thing as the bamboo rayon most baby brands describe as "bamboo." It's softer after the fifth wash than it is on day one, which is the opposite of how cotton ages.
The print. Soft cream ground with hand-drawn numerals — quiet enough for sleep, sharp enough that your sister-in-law asks where it's from.
Construction. Sleeveless, so the arms can release heat. 2-way zipper that opens from the bottom so a midnight diaper change doesn't require lifting a hot baby out of the bag. Soft fabric binding at the neck and arms — no scratchy serged edges against skin. Fits true to size at the shoulders, which is the dimension that matters for safe sleep.
Why 0.5 TOG matters. Most premium sleep-sack brands skip this weight — the lightest options on the market typically start at 0.6 or 0.7 TOG and read warmer in practice. That leaves families with warm nurseries doing one of two things — laying a blanket over the baby (which the AAP doesn't recommend) or skipping the sleep sack entirely. The 0.5 TOG muslin is the answer for both.
Need a warmer weight? The matching 1.0 TOG TENCEL™ Sleep Bag in Mini Mathletes is built for the everyday 69–75°F nursery. The 2.5 TOG winter weight picks up below 68°F.
Sizing. 0–6M (fits 8–18 lb), 6–18M (fits 18–28 lb), 18–36M (fits 28–38 lb). Always size to current weight, not age. A bag that's too large at the shoulders can ride up over the face overnight.
Care. Machine wash cold, tumble dry low. Tanboocel handles the dryer better than bamboo rayon — fewer pill bumps, less shrinkage over a year of weekly washes. Do not bleach. Do not iron the screen-printed area.
Tested and certified. Fabric carries OEKO-TEX Standard 100 certification. Garment passes CPSC, CPSIA, and ASTM safety testing. Built around the American Academy of Pediatrics safe-sleep guidance. Independent B Corp Certification on the brand.
Common questions
What temperature is 0.5 TOG good for?
0.5 TOG is the warm-room weight. Use it when the nursery sits between 75 and 81°F, typically summer nights, top-floor bedrooms, or homes without central AC. Pair with a short-sleeve bodysuit underneath.
Is muslin better than fleece for baby sleep?
Muslin breathes. Fleece traps heat. For warm-weather sleep, muslin moves humidity off the baby's skin and keeps temperature stable. Fleece sleep sacks are designed for cold nurseries and shouldn't be the default in summer.
Are baby sleep sacks safe for newborns?
Yes — once the baby is out of the swaddle phase and can roll. The AAP recommends wearable blankets like sleep sacks over loose bedding in the crib. Choose the correct TOG for room temperature and a size that fits at the shoulders so the bag can't slip over the face.
Browse all baby sleep sacks.
Free US shipping on orders over $65. Free returns within 30 days, unworn and in original packaging.
Description
Numbers, plus signs, and a small mathematician who hasn't met long division yet.
0.5 TOG. The warm-weather sleep bag. Built for nursery temperatures between 75 and 81°F — summer nights, top-floor bedrooms, homes that don't run central AC. The weight you reach for at 11 p.m. on a sweaty August night when a 1.0 TOG has your baby sweating through the back.
Material. Tanboocel viscose from bamboo and cotton, woven into an open-weave muslin. Two notes on the fiber. Tanboocel is a branded viscose-from-bamboo fiber produced through a closed-loop process that's a step beyond generic bamboo viscose — third-party verified, lower water and chemical footprint. We use it only on our 0.5 TOG muslin pieces, our swaddles, and our crib sheets. It is not the same thing as the bamboo rayon most baby brands describe as "bamboo." It's softer after the fifth wash than it is on day one, which is the opposite of how cotton ages.
The print. Soft cream ground with hand-drawn numerals — quiet enough for sleep, sharp enough that your sister-in-law asks where it's from.
Construction. Sleeveless, so the arms can release heat. 2-way zipper that opens from the bottom so a midnight diaper change doesn't require lifting a hot baby out of the bag. Soft fabric binding at the neck and arms — no scratchy serged edges against skin. Fits true to size at the shoulders, which is the dimension that matters for safe sleep.
Why 0.5 TOG matters. Most premium sleep-sack brands skip this weight — the lightest options on the market typically start at 0.6 or 0.7 TOG and read warmer in practice. That leaves families with warm nurseries doing one of two things — laying a blanket over the baby (which the AAP doesn't recommend) or skipping the sleep sack entirely. The 0.5 TOG muslin is the answer for both.
Need a warmer weight? The matching 1.0 TOG TENCEL™ Sleep Bag in Mini Mathletes is built for the everyday 69–75°F nursery. The 2.5 TOG winter weight picks up below 68°F.
Sizing. 0–6M (fits 8–18 lb), 6–18M (fits 18–28 lb), 18–36M (fits 28–38 lb). Always size to current weight, not age. A bag that's too large at the shoulders can ride up over the face overnight.
Care. Machine wash cold, tumble dry low. Tanboocel handles the dryer better than bamboo rayon — fewer pill bumps, less shrinkage over a year of weekly washes. Do not bleach. Do not iron the screen-printed area.
Tested and certified. Fabric carries OEKO-TEX Standard 100 certification. Garment passes CPSC, CPSIA, and ASTM safety testing. Built around the American Academy of Pediatrics safe-sleep guidance. Independent B Corp Certification on the brand.
Common questions
What temperature is 0.5 TOG good for?
0.5 TOG is the warm-room weight. Use it when the nursery sits between 75 and 81°F, typically summer nights, top-floor bedrooms, or homes without central AC. Pair with a short-sleeve bodysuit underneath.
Is muslin better than fleece for baby sleep?
Muslin breathes. Fleece traps heat. For warm-weather sleep, muslin moves humidity off the baby's skin and keeps temperature stable. Fleece sleep sacks are designed for cold nurseries and shouldn't be the default in summer.
Are baby sleep sacks safe for newborns?
Yes — once the baby is out of the swaddle phase and can roll. The AAP recommends wearable blankets like sleep sacks over loose bedding in the crib. Choose the correct TOG for room temperature and a size that fits at the shoulders so the bag can't slip over the face.
Browse all baby sleep sacks.
Free US shipping on orders over $65. Free returns within 30 days, unworn and in original packaging.
