What do the sleeping bag ratings mean for male and female sleepers? Are they tested?

Sea to Summit bags (like most quality sleeping bags) are tested in certified laboratories for temperature rating according to the ISO 23537. 

Published Ratings

Before we get to the details of the testing, one continual source of confusion is the difference between the Lower limit and the Comfort Rating for any given sleeping bag.

The Lower limit of a sleeping bag should be used as a guide* for male sleepers

The Comfort Rating of a sleeping bag should be used as a guide* for female sleepers

In the case of the Unisex Spark 15°F / -9°C

the Lower limit is 15°F / -9°C - which is what a male sleeper should use for orientation*

the Comfort Rating would be 29°F / -2°C - which is what a female sleeper should use for orientation*

(So - a woman sleeper purchasing this Unisex sleeping bag should really think of it as a "Spark 29")

Because of misperception, some women purchase the Unisex Spark over the Women's Spark (or the Ascent over the Women's Ascent) believing them to be 'lighter but just as warm'.

The Women's Spark 15°F / -9°C has the following ratings:

the Lower limit would be 5°F / -15°C - which is what a male sleeper should use for orientation*

the Comfort Rating is 15°F / -9°C - which is what a female sleeper should use for orientation*

Why the asterisk above next to 'guide' and 'orientation'?

Because the 'Lower Limit' and Comfort Rating' are not guaranteed temperatures; they are guidelines.

- Different people perceive cold differently. A male sleeper who 'sleeps cold' may care to use the 'Comfort Rating' rather than the 'Lower Limit' as an indication of the appropriate sleeping bag for his use.

Because the published temperature ratings require a sleeper to use a sleeping pad with adequate insulation, and be dressed in appropriate clothing

- Please see the 'How sleeping bags are tested' below

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All Sea to Summit Unisex Sleeping Bags are listed using the LOWER limit, which is appropriate for male sleepers. Women end-users should use the COMFORT rating of a Unisex bag.

All Sea to Summit Women's Specific Sleeping Bags are listed using the COMFORT rating. 

How sleeping bags are tested to the ISO standard

The test is conducted using a heated manikin inside the sleeping bag in a cold chamber. Measurements are taken to determine how much warmth the sleeping bag retains.

The manikins are dressed in Expedition Weight base layers with an insulating cap.

The sleeping pad used has an R-Value of over 5

If you are not dressed in layers as warm as above, you will not achieve the published rating

If you use a sleeping pad which has an (ASTM tested) R-Value of less than 5, you will not achieve the published rating

- this is true regardless of metabolism or other factors