Many sleeping bags are rated using the EN13537 rating which is a European Standard designed to standardise temperature ratings across sleeping bags regardless of manufacturer.
Generally 3 temperatures are provided, Women's Comfort, Men's Limit & Extreme.
- The Women's Comfort is the temperature at which a "Standard Woman" can sleep comfortably in a relaxed position.
- The Men's Comfort Limit is the temperature at which a "Standard Man" can sleep for 8 hours in a curled position.
- And Extreme is the minimum temperature at which a "Standard Woman" can remain for 6 hours without risk of death, but the risk of frostbite is still possible. At this temperature you will be cold, you will be uncomfortable, you will probably not sleep, and there is the risk of serious injury. We suggest you avoid buying a sleeping bag based on this temperature.
- A Standard Woman is assumed to be 25 years old, 160cm tall and with a weight of 60kg.
- A Standard Man is assumed to be 25 years old, 173cm tall and with a weight of 73kg.
- These ratings are given assuming the subject is using an insulated sleeping mat, is in a tent and is wearing one layer of long thermal underwear.
What if the sleeping bag doesn't have an EN13537 rating?
Several Mont sleeping bags do not carry an EN13537 rating, rather they have a Mont Temperature Rating. A Mont Temperature Rating is based on over 35 years of experience in the design, manufacture and use of sleeping bags in the wild.
On a Mont Temperature Rated sleeping bag two temperatures are given, a warmer temperature and a colder temperature. These two temperatures can be considered in a similar way to the Women's Comfort and Men's Limit temperatures specified on EN13537 rating.
For example, the Mont Spindrift Sleeping Bag has a temperature rating of -9ºC to -15ºC. This rating suggests a Woman or someone who sleeps very cold will be comfortable at -9ºC or just below, and a Man or someone who sleeps warm will be comfortable at -15ºC.
We always suggest buying a sleeping bag with a temperature rating that will go below what you expect to face. It is much easier to cool down than it is to warm up.
Other factors that will determine your comfort in a sleeping bag are metabolism, age, thermals, socks, headwear, health, fatigue, what you have eaten and what type of sleeping mat used.
Other blog posts about Sleeping Bags.
Why do sleeping bags have left & right zips & which do I choose?
What size sleeping bag do I need?
How to look after your down sleeping bag