When purchasing a new sleeping bag, you usually check the temperature rating to see if the bag fits your needs. Is this the best way to choose a bag? Generally not. A rating may be good for one person, but not for another.
Humans differ in the amount of body heat produced and the amount of heat retained. A sleeping bag traps body heat in the insulation, keeping you warm when you sleep and your body cools during this period.
Ever wonder what temperature rating is best for you? There are a number of tricks and tips you need to know about temperature ratings. You would think a bag rated for 0 degrees, would keep you warm at that temperature. This is not always the case.
A good rule of thumb is to purchase a sleeping bag that is rated at least 20 degrees below the lowest temperature you are likely to encounter. Another is to use the “EN rating”, this is more of a real world rating.