How to Choose a Sleeping Bag

1. Temperature rating — the one that counts

Every bag has a number, like "20°F." Here's the part nobody explains: that's usually the survive number, not the sleep-comfortably number. The rating tells you the lowest temperature at which an average sleeper won't get dangerously cold — not the temperature at which they'll be cozy.

So buy a buffer. Pick a bag rated about 10°F below the coldest night you expect. Planning for 40°F nights? A 30°F bag. It's always easier to vent a too-warm bag (unzip it) than to survive a too-cold one.

This matters double for kids: small bodies lose heat faster than adults, so round down on the rating and never assume a kid will be fine in a bag rated for the exact forecast.

2. Shape — roomy or warm, pick your trade-off

Rectangular bags are the roomy ones. You can roll over, stretch out, even unzip them flat like a blanket. They're heavier and a touch cooler (more air to heat), which is a non-issue for car camping where you're not carrying it far. For most families, this is the comfortable, kid-friendly choice.

Mummy bags taper toward the feet and have a hood that cinches around your head. Less room, but far warmer and lighter — they're built for backpacking and cold nights. A fidgety kid may feel trapped in one; a Scout heading into the cold will be glad of it.

There are semi-rectangular bags that split the difference if you can't decide.

3. Fill — down vs. synthetic

Down (goose or duck feathers) is the warmest for its weight and packs down tiny. The catches: it's pricey, and it loses its warmth when wet and is slow to dry. Wondering if you even need down? See do you need a down sleeping bag?.

Synthetic fill is cheaper, keeps you warm even when damp, dries fast, and shrugs off rough handling and frequent washing. It's bulkier and a bit heavier — and for that reason it's usually the smarter pick for kids and for anyone camping somewhere that might get wet. Spills, mud, and accidents wash out without drama — see our guide on how to wash a sleeping bag.

For a first family setup, synthetic is the low-stress, low-cost answer almost every time.

4. Size and fit — especially for kids

A sleeping bag keeps you warm by heating the air inside it. Too much empty space, and your body wastes energy warming room you're not using — which is exactly why a child swimming in an adult bag often sleeps cold despite the rating.

That's the case for a kid-specific bag: it's shorter, so there's less dead air to heat, and many cinch down further as they grow. If you do put a child in an adult bag, push a stuff sack or spare clothing into the foot to take up the slack. Check the manufacturer's age and size guidance, and keep loose bedding away from infants entirely — bags are for kids who already sleep on their own, not babies.

Putting it together

For a typical family weekend in mild-to-cool weather: a rectangular, synthetic bag rated about 10°F below your expected low, in a kid-sized version for the little ones. Comfortable, affordable, washable, and warm enough with margin to spare. Save the mummy-and-down debate for when someone in the house gets serious about backpacking.

Ready to buy? Here are the three kids' sleeping bags we'd actually hand a family.