Sleeping bag temperature guide
Sleeping bags list several temperatures, and reading the wrong one means a cold night. Enter how cold it will get and how quickly you feel the cold. The guide tells you which comfort rating to look for.
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How the calculation works
Sleeping bags are tested to EN ISO 23537. The label shows comfort, limit and extreme temperatures. The comfort rating is the one to choose by: down to it, a person who feels the cold sleeps relaxed without shivering.
The guide subtracts a safety margin from the expected overnight low: 8 degrees if you feel the cold quickly, 5 degrees if you are average and 2 degrees if you sleep warm. These margins are our recommendation and allow for things like damp air or tiredness.
How to read the result
The figure is the highest comfort rating your bag should have. A bag with a lower comfort rating is warmer and fits too.
The limit rating is not a comfort threshold. Rely on it and you will usually sleep curled up and still be cold.
Frequently asked questions
How much does the sleeping mat matter?
A lot. The ground draws heat out of you that no sleeping bag can make up for. In the cold, choose a mat with a high R-value.
Down or synthetic?
Down is warmer for its weight and packs smaller. Synthetic fill copes better with damp and dries faster.
How do I find the overnight temperature?
From the forecast for the place and altitude. On average it gets about 0.65 degrees colder per 100 metres of height, often much more on clear nights.