Put a pad, a bag, and a pillow together and see the whole kit at once: total weight, packed size, and price, plus the one number a spec sheet never gives you, the temperature the system actually sleeps to once the pad and bag are working together. Data, not opinions.
A sleep system rides inside a shelter, and the pad is where two people run out of floor. Drop your pad, or a pair, into a tent's real floor shape and see the clearance at the head, the foot, and each wall, drawn to scale. Data, not guesswork.
Why the pad decides how warm your bag really is
On a cold night most of your body heat does not escape into the air, it drains straight down into the ground, because your weight flattens the bag insulation underneath you until it does almost nothing. The sleeping pad is what stops that loss, and its R-value is the measure of how well. That is why a 20°F bag on a thin summer pad can leave you shivering at 35°F: the bag is fine, the ground is winning. A sleep system is only as warm as its weaker half, so this tool scores the pad and the bag together and tells you which one is holding the system back.
How it works
Set your priorities
Tell it your coldest night and how much weight, packed size, and price matter. Every match score and the ranked shortlist update the moment you move a slider, and the best system fills itself in.
See the whole kit at a glance
Total weight, packed size, and price for the complete system, each on a colored meter, plus the temperature it really sleeps to, drawn on a scale. Swap any piece and it all recomputes.
Read the warmth honestly
The temperature strip plots the bag rating and the pad support side by side, so a mismatch is something you see, not a number you have to hunt for, and it names the fix.
Common questions
Does my sleeping pad affect how warm my sleeping bag is?
Yes, a lot. Most of the heat you lose on a cold night goes straight down into the ground, and a sleeping bag does almost nothing to stop that, because your body crushes the insulation underneath you flat. The pad is what blocks that ground loss, and its R-value measures how well it does it. So a warm bag on a thin pad still sleeps cold. Your system is only as warm as its weaker half, which is exactly what this tool checks.
What R-value pad do I need for a 20°F bag?
Roughly R4 or higher. As a rule of thumb, R2 is about freezing, R3 is around 20°F, R4 is around 10°F, and R5 is near 0°F. A 20°F bag paired with an R2 pad will leave you cold well before 20°F, because the ground pulls heat faster than the pad can hold it. The builder computes the exact pairing and tells you the R-value that matches your bag.
How is the system comfort temperature calculated?
We start from the bag standardized comfort rating (lab EN or ISO where published, adjusted to a comfort-equivalent otherwise), then limit it by the temperature the pad can actually support at its R-value. The colder of the two capabilities is the honest floor for the system. If the pad is the weak link, the tool says so and gives you the fix.
Does the pillow change the warmth number?
No. A pillow adds a little weight, packed size, and cost to the system, but it does not change how cold a night you can sleep through, so it never moves the warmth verdict. It is in the builder because a complete sleep system is pad, bag, and pillow, and the weight and price of all three are what you actually carry and pay.
What is a reasonable weight for a full sleep system?
It depends on the season and your budget, which is the point of the recommender. As a reference, a light three-season pad, bag, and pillow together land in the low-to-mid 40-ounce range (under 3 pounds), while warmer or more comfort-focused kits run heavier. Set your priorities and the tool finds the lightest, smallest, or cheapest system that still hits your warmth target.
Warmth pairing uses each bag standardized comfort rating (lab EN or ISO where published, or a documented comfort-equivalent adjustment otherwise) and a published R-value-to-temperature guide for the pad. It is a real-world estimate to size a system, not a guarantee for a specific night, body, or setup. Weights, packed volumes, and prices are the manufacturers published figures; blanks are shown as not stated, never guessed.