There is no standardised test for the warmth a liner adds, so any rating would be an educated guess.
Sleeping bags are tested to the ISO standard and mats to the ASTM standard, but no protocol exists for liners.
Testing a liner inside one bag would only describe that bag and mat combination.
The boost depends on many variables, including how well the sleeping bag retains heat and how well the pad insulates.
A moving sleeper also loses heat in ways a static test doesn't.
Articles in this section
- Why don't you list additional temperature ratings with liners?
- Do any Sea to Summit sleeping bag / travel liners have side zippers?
- Which sleeping bag liner should I choose?
- Are your sleeping bag liners treated with flame retardants?
- What is the silk and cotton blend ratio in the Silk Blend Liner?
- Why should I use a sleeping bag liner?