Sleep Sack TOG Ratings by Temperature (2026): Picking the Right Weight for the Room

A sleep sack is a wearable blanket that replaces loose bedding in the crib, which the AAP has identified as a leading suffocation risk for infants under 12 months. The two questions most parents have to answer for every season are: which TOG rating fits the nursery temperature, and what does the baby wear underneath. Getting this wrong produces either a fussy, overheating baby (the more common error) or a baby who wakes every hour because the room is too cold. This guide turns it into a temperature chart with concrete dressing pairings.

What TOG actually measures

TOG is a thermal resistance value used in the European bedding industry. A 1.0 TOG fabric has roughly the warmth of a long-sleeve shirt. A 2.5 TOG sack roughly equals a winter blanket with a long-sleeve pajama underneath. The scale runs from 0.2 (lightest, hot summer rooms) to 3.5 (heaviest, cold winter nurseries).

Sleep sack brands sold in the US (Halo, Kyte Baby, Woolino, ergoPouch, Nested Bean) usually print the TOG rating on the package and tag. Brands that do not display a TOG number are usually equivalent to 0.5 or 1.0 TOG.

The temperature chart

The following chart is the most common version sold by major sleep sack manufacturers. Verify the specific number on your sack’s tag, as exact recommendations vary slightly between brands.

Room temperature	TOG rating	Layer underneath
74-78 F (23-26 C)	0.2 to 0.5 TOG	Short-sleeve bodysuit only
69-74 F (21-23 C)	1.0 TOG	Short or long-sleeve bodysuit
64-69 F (18-21 C)	2.5 TOG	Long-sleeve, full-leg pajamas
Below 64 F (below 18 C)	3.5 TOG	Long-sleeve, full-leg pajamas plus socks

The AAP-recommended sleep temperature range is 68 to 72 F, so for most homes a 1.0 TOG with a long-sleeve bodysuit underneath is the year-round default. Houses that swing colder in winter or warmer in summer need a second sack.

A two-sack starter set covers most homes

A practical year-round set is:

• One 1.0 TOG sack for spring, fall, and most of summer (in an air-conditioned home)
• One 2.5 TOG sack for winter or unheated nurseries

A third 0.5 TOG sack helps in homes without central air or in climates where summer nursery temperatures reach 78 F or higher. A 3.5 TOG sack is rarely necessary in the US except in unheated rooms or for parents who keep the thermostat below 65 at night.

Sleep sacks are sized by age (0 to 3 months, 3 to 6 months, 6 to 12 months, 12 to 24 months). Babies typically use 3 to 4 sacks total over their first 24 months. A bulk-buying mistake is to buy multiple sacks in the same size, which means they outgrow the entire stash at once.

Underneath the sack, the layering rule

The classic guideline used by pediatric nurses: dress the baby in one more layer than an adult would wear comfortably in the same room. A sleep sack counts as one layer. A long-sleeve onesie counts as one layer. Pajamas with feet count as one layer.

Examples:

• Room at 70 F, you wear a t-shirt: baby in a short-sleeve bodysuit and a 1.0 TOG sack
• Room at 66 F, you wear long sleeves and a light blanket: baby in long-sleeve footed pajamas and a 2.5 TOG sack
• Room at 76 F, you wear shorts and a t-shirt: baby in a sleeveless or short-sleeve bodysuit and a 0.5 TOG sack

Avoid layering a sweater or fleece under a sack. Trapped warmth between layers raises core temperature faster than a single warmer outer layer.

How to tell if the baby is too warm

The fingers and toes of a newborn are almost always cool because circulation prioritizes the core. Touching the hands is the wrong test. The reliable spots are:

• The back of the neck or upper chest (should feel warm but not hot)
• The back between the shoulder blades (should feel dry, not damp)
• The hairline (should not be matted with sweat)

Signs of overheating include damp hair, flushed cheeks, rapid breathing, and restlessness. Strip a layer immediately. Overheating is a documented contributor to sleep-related infant death and is one of the few risk factors parents can directly control.

Swaddles vs sleep sacks vs transition sacks

A swaddle is wrapped tightly around the baby’s arms and torso, used for the first 8 to 12 weeks. Once the baby shows signs of rolling, the swaddle becomes unsafe and the baby moves to either:

• A sleep sack with arms free
• A transition product like the Merlin Magic Sleepsuit or Love To Dream Swaddle Up 50/50, which gradually weans from swaddling

Sleep sacks for arms-out use start at 3 months and continue through the toddler years. There are even sacks with foot holes that allow the toddler to walk to a parent’s bed in the morning without tripping.

Common materials and what they mean for TOG

• Cotton muslin: Light, breathable, typically 0.2 to 0.5 TOG. Good for hot months.
• Cotton jersey or quilted cotton: Most common, typically 1.0 TOG.
• Bamboo viscose (Kyte Baby): Soft, moisture-wicking, available in 1.0 and 2.5 TOG.
• Merino wool (Woolino): Temperature-regulating, often marketed as a single-sack year-round solution. Effective TOG sits around 1.0 to 1.5.
• Down or polyester fill: Used in 2.5 and 3.5 TOG sacks, warmer but less breathable.

Merino wool sacks are the most flexible across seasons because the fiber adjusts to body temperature, but they are also the most expensive ($110 to $160 versus $25 to $45 for cotton).

A practical purchase plan

For a newborn arriving in spring or summer:

• One Halo Sleepsack Swaddle 0.5 TOG for the first 8 weeks
• One Kyte Baby or Halo 1.0 TOG sack in 0 to 3 months once arms come out
• A 2.5 TOG sack in 3 to 6 months for fall and winter

For a newborn arriving in fall or winter:

• One Halo Sleepsack Swaddle 1.5 TOG for the first 8 weeks
• One 2.5 TOG sack in 0 to 3 months for arms-out use in a cool nursery
• A 1.0 TOG sack in 3 to 6 months for warmer months

For more on the broader nursery setup, see our bassinet vs co-sleeper decision guide and hospital bag essentials checklist.

Frequently asked questions