Sleeping Bag Temperature Rating Calculator
Estimate the sleeping-bag comfort rating you need from the coldest night you expect and your cold tolerance.
How it works
target rating = expected low − cold-tolerance buffer + liner credit
Sleeping-bag comfort ratings assume a warm sleeper on an insulated pad, so buying a bag rated exactly at the night’s low often leaves cold sleepers shivering. The safe approach is to pick a comfort rating below the coldest temperature you expect, with a larger buffer if you sleep cold. A thermal liner adds roughly 5–15°F of warmth and is credited here at 10°F, and a warm sleeping pad is just as important as the bag itself.
Worked example
Expecting a 30°F low as an average sleeper adds a 10°F buffer for a 20°F target. With a thermal liner (+10°F), a bag rated near 30°F comfort would suffice.
Frequently asked questions
What is the difference between comfort and limit ratings?
The EN/ISO comfort rating is the lowest temperature a “cold” standard sleeper stays comfortable; the lower limit is where a “warm” sleeper is on the edge. Shop by the comfort rating to be safe.
Why buy a colder rating than the forecast?
Ratings are lab figures under ideal conditions. Wind, humidity, fatigue and an inadequate pad all make real nights feel colder, so a buffer keeps you warm.
Does my sleeping pad matter?
A lot. Much of your heat loss goes into the ground, so a pad with an adequate R-value is essential — a warm bag on a thin pad still sleeps cold.
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This calculator is for educational purposes. Double-check important results before acting on them.