Northern Warmth

Why We Don't Print Temperature Ratings

Almost every sleeping bag in our price range carries a temperature figure on the label. Ours do not. This page explains why — and what we give you instead.

What a temperature rating is supposed to mean

There is a proper standard for this: ISO 23537-1 (previously EN 13537). A bag is placed on a heated mannequin in an accredited laboratory, and the test produces three figures — comfort, limit and extreme. When a manufacturer publishes those numbers and can show the test report, the figures mean something and bags can be compared.

The standard is voluntary. Nobody is legally required to test.

What usually happens instead

A bag is bought from a factory, the factory’s own claim is copied into the listing, and the number travels from shop to shop untested. Look across our price band and you will find the same physical bag sold as −10 °C by one shop and −20 °C by another. Both cannot be right. Neither has a report.

We would have to do the same thing to print a number, so we don’t print one.

What we publish instead

Every listing states the measurements that actually determine how warm a bag is:

Fill weight in grams — how much down is actually inside. More down, more trapped air, more warmth.
Down-to-feather ratio — down clusters loft, feathers do not. The ratio tells you what you are paying for.
Shell fabric — what holds the down in and sheds condensation.
Total weight and packed size — what you actually carry.

And we describe the conditions in plain words: which season, which kind of night, what the bag is not intended for.

Why this is more useful, not less

A comfort figure is a single number that hides everything. Fill weight is comparable across every bag on the market, including tested ones: you can put our 800 g against a laboratory-tested bag and see immediately where it sits.

The trade-off is that you have to read two lines instead of one. We think that is a fair exchange for a number that is actually true.