Sleeping Bag Rating Calculator

It subtracts a safety margin from the expected low based on how you sleep: nothing for a warm sleeper, 10 degrees F for an average sleeper and 15 degrees F for a cold sleeper. So a 30 F night gives 30 F for warm, 20 F for average and 15 F for cold sleepers.

People who sleep cold lose body heat faster overnight, so they need a bag rated further below the conditions to stay comfortable. The tool subtracts the largest margin, 15 degrees F, for that group.

Standardised EN 13537 and ISO 23537 tests report a comfort rating, where a cold sleeper stays warm, and a lower limit rating for a warm sleeper curled up. Shop by the comfort rating, especially if you run cold, rather than the headline lowest number.

Yes. Toggle the unit to degrees C and enter the low in Celsius. The tool converts your figure to Fahrenheit internally, applies the margin, then shows the recommended rating and margin back in Celsius.

No, they are a planning guideline. Actual warmth depends on your sleeping pad, clothing, tent, humidity, wind, food intake and the bag's real tested rating, none of which a single input can capture.

A great deal. A pad's R value blocks heat draining into the cold ground, and a warm bag on a thin pad can still sleep cold. Match the pad's R value to the season alongside the bag rating.

A sleeping bag liner can add several degrees, and wearing dry base layers, a hat and dry socks helps a lot. A bag rated close to the low leaves little margin, so these extras bridge the gap on an unexpectedly cold night.

Down is lighter and packs smaller for the same warmth and lasts longer if cared for, while synthetic is cheaper and keeps more of its warmth when damp. The rating you target here applies to either fill type.

No. The recommendation is calculated in your browser as you change the inputs, so nothing you type is sent to a server and the tool works offline once loaded.