Sleeping Bag Temperature Calculator
Calculates the right rating for your specific conditions — not just the forecast temperature.
Night conditions
Recommended rating
Summer8°C
Lower limit rating — suitable for most male hikers
What this means
A 3-season bag is your best option
These are the most versatile bags available. Look for a comfort rating at or below 8°C. Down fill gives better warmth-to-weight, synthetic is fine if conditions might be damp.
What to look for: comfort rating 2°C or lower, lower limit 8°C or lower.
Where your rating falls
Breakdown
Find a bag rated to 8°C
Based on your inputs, this is the temperature rating that will keep you comfortable. Look for this number on the bag's EN/ISO certification tag.
Find on Amazon →How to use the sleeping bag calculator
Enter your expected overnight low temperature and whether you sleep warm or cold. You'll get a recommended temperature rating straight away. Open Advanced Options to refine for altitude, shelter type, sleeping pad R-value, and liner use.
What affects sleeping bag temperature needs
The EN/ISO rating system
Most manufacturers display the lower limit rating as the headline number. That's the temperature at which a warm male sleeper can survive the night. If you sleep cold, or you're female, you need the comfort rating, which is typically 6-8 degrees warmer. This calculator adjusts for both.
Altitude
Cold air at altitude holds less moisture, which means your body loses heat faster than the thermometer suggests. Add a meaningful buffer above 2,500m. At 4,000m and above the difference can be several degrees of effective temperature.
Your sleeping pad
A low R-value pad lets ground cold bypass your bag's insulation entirely. If your pad is R2 or below, upgrading it will improve your sleep system more than buying a warmer bag. The calculator factors this in and flags it when your pad is inadequate for the conditions.
Cold vs warm sleepers
This is real physiology, not a preference. Metabolic heat production during sleep genuinely varies between people, and research consistently shows women trend colder than men. Buy by the comfort rating if you know you sleep cold.