As an Amazon Associate I earn from qualifying purchases. Product links below are affiliate links.
A sleeping bag’s comfort and limit ratings describe different test conditions. For choosing a bag, start with the comfort figure and your own experience of sleeping warm or cold. Do not use the lowest number on the label as the temperature at which you should expect a comfortable night.
Table of Contents
Understand the three common figures
Rab’s temperature-rating explanation describes standardised comfort, limit and extreme measures. Comfort represents a more relaxed sleeping condition; limit reflects a warmer reference sleeper in a curled position. Extreme is a survival-related figure and is not a target for normal camping use.
The standard uses reference conditions and body models. Real people vary, so the labels are guidance rather than personal guarantees. If you know you sleep cold, use that experience when allowing a margin below the expected overnight temperature.
Read a real product label carefully
The current Rab Ascent −6°C lists comfort at 0°C, limit at −6°C and extreme at −24°C. The number in the product name therefore matches its limit figure, not its comfort figure.
You can check the current Ascent −6°C listing on Amazon UK. Confirm the exact generation and size, and compare the full manufacturer table rather than relying on the retailer’s headline temperature field.
Include the mat and clothing
A sleeping bag is only part of the sleep system. The mat supplies insulation beneath you, and the test arrangement does not reproduce every campsite surface, clothing choice or shelter condition. Check mat insulation separately from thickness and comfort.
Keep sleepwear and bedding dry. Avoid assuming that an extra blanket, liner or another person’s body heat will add a fixed number of degrees to the rating. Those changes do not create a newly tested temperature specification.
Use the forecast for the actual location
Check overnight conditions near the campsite, not just the nearest town’s daytime maximum. Consider how exposed the pitch is and whether the forecast is changing. If the conditions fall outside a setup you can use comfortably and safely, choose more suitable equipment or change the trip.
A season label such as three-season is less precise than the temperature table. It may help describe intended use, but it should not replace the actual comfort figure when comparing products.
Make a clear buying comparison
- Compare comfort ratings measured under a stated standard where available.
- Keep limit and extreme figures in their proper roles.
- Check the exact model rather than a similar product name.
- Allow for personal sleeping experience and the rest of the sleep system.
The useful question is whether the complete setup suits your expected night with a sensible margin. Choosing by the most dramatic negative number can lead to the wrong bag.
Continue with our sleeping bag buying guide.
Reviewed 10 September 2026. This guide is based on published specifications and guidance.