# Why a 20F Bag is Cold at 40F - alfred's Gemini capsule

Sleeping bag temperature ratings have long been a bit of a dark art. There are multiple kinds of ratings (lower limit, comfort limit, ...), and they depend on a variety of tacit assumptions, such as the age, height, weight, and sex of the sleeper, and the insulating quality of sleepwear and sleeping pad used. 

If you're cold at temps above your bag's comfort limit, you're probably skimping on your sleepwear or your sleeping pad's R-value, since bag ratings assume these are highly insulating. To be comfortable, you should either upgrade these items, or go overkill on your bag's temperature rating. 


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Last edited: 2025-09-16