Guide 3 min
What temperature sleeping bag do you need?
Your night hits 0 °C in spring, 10 °C in summer, and drops 6 °C per 1000 m. Start from that figure to pick the right comfort rating.
The rule fits in one sentence: the comfort rating of your sleeping bag should be equal to or lower than the night you're about to spend. And that night, you can put a figure on it before you leave, no thermometer needed: start from the season (0 °C in spring and autumn, 10 °C in summer, -5 °C in winter) and take off 6 °C for every 1000 m of altitude.
The trap works the other way too: a bag that's too warm is dead weight for nothing. WildKit rules out any bag whose comfort rating sits more than 8 °C below the night you expect. The right bag is the one that covers your night without going far past it.
Put a figure on your night before you look at bags
It all starts from the season, in the lowlands:
| Season | Night in the lowlands |
|---|---|
| Spring | 0 °C |
| Summer | 10 °C |
| Autumn | 0 °C |
| Winter | -5 °C |
Then altitude pulls the temperature down: take off 6 °C per 1000 m. In the mountains, the night drops fast. In spring at 1500 m, you go from 0 °C to -9 °C (0 minus 6 × 1.5). That figure, not the season on its own, is what your bag has to cover.
Aim for a comfort rating equal to or below your night
Once you've put a figure on your night, the bag almost picks itself: its comfort rating should sit at your night, or below.
| Your trip | Night expected | Comfort rating to aim for |
|---|---|---|
| Summer in the lowlands | 10 °C | 10 °C or lower |
| Spring at 1500 m | -9 °C | -9 °C or lower |
| Winter in the lowlands | -5 °C | -5 °C or lower |
A comfort rating above your night, and you shiver. The safety margin is to aim a little below, never above.
Comfort rating, not the headline limit
Many product pages push the "limit" or "extreme" rating, the one where you survive without sleeping, because it makes for a nicer number. WildKit works on the comfort rating: the temperature at which you actually sleep, without waking up frozen. That's the only figure to compare against your night.
Don't take a bag that's too warm either
Oversizing costs you dearly in weight and volume. A bag built for far colder than your night doesn't keep you any warmer: it weighs for nothing, and that weight lands on your back (see the target weight for each trip). Example: on a summer night in the lowlands at 10 °C, a bag rated 0 °C for comfort is oversized by 10 °C. Past an 8 °C gap, WildKit rules it out.
The bag doesn't do it all: under your body, it's the sleeping mat that blocks the cold coming off the ground, and the two are worked out together (see sleeping bag and mat for a cold night).
What to remember
- Your bag's comfort rating should be equal to or lower than the night you expect.
- Put a figure on your night: season (0 spring and autumn, 10 summer, -5 winter) minus 6 °C per 1000 m.
- Too warm costs weight: past an 8 °C gap with your night, the bag is ruled out.
A bag picked on an optimistic label leaves you shivering in the middle of the night, with nothing to warm you up out there. Give your season and your altitude to the configurator: it puts a figure on your night and suggests the bag whose comfort rating covers it, without going more than 8 °C past it.
A guide WildKit keeps up to date. Published .