Sleeping Bag Comfort vs Limit Rating: Compare the Right Temperature
Compare Comfort with Comfort and Lower Limit with Lower Limit. The temperature in a sleeping bag’s product name may use either field. It does not, by itself, tell you which condition was tested or how warm you personally will sleep.
Sea to Summit provides a useful exact-product example: its unisex Spark names follow Lower Limit, while Women’s Spark names follow Comfort. Two bags sold as “15°F” therefore point to different ratings. The table below keeps both fields and preserves the current product tables’ displayed values, including small differences from the model names.
Identify which number you are reading
| Field on the label | How to use it in a comparison | What it cannot establish |
|---|---|---|
| Comfort | A comfort reference associated with a standardized female sleeper in the manufacturer’s explanation. Compare the same field across products. | A guarantee for every sleeper with that sex or body type. |
| Lower Limit / Limit | A different reference associated with a standardized male sleeper. Keep it separate from Comfort. | A universal comfortable sleeping temperature or an interchangeable Comfort value. |
| Product-name temperature | A name whose basis must be checked in the specification. | An independently verified test field when no basis is supplied. |
| Extreme, if listed | A separate warning category; exclude it from a comfort comparison. | A target for routine trip planning. |
Swipe or scroll sideways to see all columns.
A sleeper who tends to feel cold may care more about the Comfort field regardless of the product’s gender label. The useful record is the exact specification plus the sleep system and person it will serve, not a rule that every buyer belongs to one test reference.
Compare six named models using their actual specifications
| Family / named model | Size | ISO Comfort: °C / °F | ISO Lower: °C / °F | Source |
|---|---|---|---|---|
| Spark 45°F | Regular | 11 / 52 | 7 / 45 | Manufacturer |
| Spark 30°F | Regular | 4 / 39 | -1 / 30 | Manufacturer |
| Spark 15°F | Regular | -2 / 28 | -9 / 16 | Manufacturer |
| Women's Spark 45°F | Regular | 7 / 45 | 4 / 39 | Manufacturer |
| Women's Spark 30°F | Regular | -1 / 30 | -7 / 19 | Manufacturer |
| Women's Spark 15°F | Regular | -9 / 16 | -15 / 5 | Manufacturer |
Swipe or scroll sideways to see all columns.
Download the exact-field comparison (CSV). All rows are Regular size. The pages identify ISO ratings but do not state an edition alongside these values; that edition remains unconfirmed in the download.
Notice the 15°F naming and rounding differences
The current unisex Spark 15°F Tech specs row displays Comfort −2°C / 28°F and Lower −9°C / 16°F. The Women’s Spark 15°F row displays Comfort −9°C / 16°F and Lower −15°C / 5°F. Read across the same column to compare them; matching names do not mean matching results.
The manufacturer’s support explanation uses rounded examples of 29°F Comfort for the unisex 15°F model and 15°F Comfort for the women’s model. We keep the exact current product-table entries above rather than silently changing them to match that example or recalculating one unit from the other. If a specific purchase hinges on the difference, confirm the label on that exact bag with the manufacturer.
Check the conditions behind the label
Sea to Summit describes a heated-manikin test with insulating clothing, a cap and a sleeping pad rated above R-5. That is a stated laboratory setup, not a claim that a bag provides the same result on any pad or in any clothing. Personal cold sensitivity and the complete sleep system still matter.
The public scope of ISO 23537-1:2022 covers adult leisure sleeping bags within its stated temperature range; it excludes children’s and babies’ bags and certain specialist uses. A product page saying “ISO” does not establish which edition or report applies. This article compares adult product labels and does not calculate a personal safe minimum.
Use this short label audit before buying
- Keep the exact family, named temperature, size and version together.
- Write down both Comfort and Lower Limit, in their original units. Mark missing values as unconfirmed.
- Record the stated standard, edition and test report when provided. Do not label an unspecified manufacturer rating as ISO-tested.
- Ask which rating the headline number uses and compare that same field across your shortlist.
- Keep pad insulation, clothing and bag fit in the decision. Do not add a fixed number of degrees for an accessory without product-specific evidence.
A missing Comfort value cannot be recovered by adding a standard offset to Limit. If a seller only supplies “20°F,” request the underlying field and test basis before treating it as equivalent to a fully documented model.