Kids' sleeping kit
The calculator needs JavaScript. The worked example, sum and figures below show exactly how it works, so you can do it yourself. A guide, not advice.
Short answer
Compare your child's height with the sleeping bag's usable inside length, and check its comfort rating against the forecast low. These figures are prompts to check the bag maker's child-specific guidance; they do not determine whether a bag is suitable or predict comfort. Check the mat and sleepwear as part of the whole sleep system.
Worked example
| You enter | Value |
|---|---|
| Child's height | 1.25 m |
| Bag's usable inside length from its maker | 1.5 m |
| Forecast overnight low | 7 °C |
| Bag comfort rating | 5 °C |
| Child's mat R-value | 2.5 |
The entered comfort rating is at or below the forecast low.
| Result | Value |
|---|---|
| Length difference | 0.25 m (bag longer than child's height) |
| Bag rating comparison | The entered comfort rating is at or below the forecast low. |
| Kit details to check | Check the mat's fit and label (R-value 2.5); it is part of the sleep system. |
Show the working
- Bag length 1.5 m − child height 1.25 m = 0.25 m
- Bag comfort rating 5 °C compared with forecast low 7 °C
How it works
- Length difference = the bag's usable inside length − the child's height
- Compare the bag comfort rating with the forecast low
- Follow the bag and mat makers' age, size and care guidance
This comparison does not decide whether a bag is suitable for a particular child. Check age guidance, fit, sleepwear and the maker's instructions; keep children's faces uncovered and avoid overheating.
Our figures (adjustable)
These are our planning allowances and, once checked, typical figures with their sources. They aren't facts about your kit: change any of them in the calculator.
This calculator has no built-in defaults: every figure comes from you or your kit's own label.
What to buy
Shopping links will appear here once our retailer partners are confirmed. We don't rank kit by testing it: see our spec-based kit guides.
FAQs
How much room should a child have in a sleeping bag?
Follow the bag maker's age and size guidance. A bag that is too large or too small may not work as intended; this calculator only compares dimensions you enter.
Which temperature rating should I use?
Use the comfort rating on the label and read the maker's explanation. A rating is not a guarantee of comfort for an individual child.
Guides that use it
Kids' sleeping bags: sizes and warmth
Kids' sleeping bags: choose by the maker's height range, bag shape and expected conditions, and read the comfort figure rather than an extreme one.