A sleeping pad is an integral part of a backpacker's sleep system. It provides comfort and warmth to the hiker by separating them from the ground.
Foam Sleeping Pads
The two main distinctions between sleeping pad are the materials, which are most commonly either foam or inflatable. Foam sleeping pads can either roll or fold up and offer minimal comfort and insulation compared to inflatable pads, however, they are often lighter and less expensive.
Inflatable Sleeping Pads
Inflatable sleeping pads come in all shapes and sizes and provide cushioning and a better opportunity to insulate the hiker, but are often pricier. Because they are inflatable, one pro is that they will pack down to a very small size compared to a foam pad that just rolls up and frequently is attached to the outside of the hiker's pack, but also requires some extra effort because it needs to be inflated, either by mouth or using a pump.
R Value
The R value of a sleeping pad is a number assigned to it that is somewhat standardized to help consumers understand how warm they should expect to be using a given sleeping pad. The greater the number, the warmer the person will sleep. 2 would be on the low end of insulation for a sleeping pad, while 6 would be on the very high side. Sleeping pads with a higher R value are necessary for winter backpacking especially.
Pumps
Sleeping pads may come with a pump sack, which is a separate cloth item that attaches to the valve of the sleeping pad. This pump sack is easier to inflate because it has a large opening, and then the air is easily pushed into the pad, inflating it faster and with less effort than blowing it up directly. For thru-hikers, this may be a welcomed luxury having to blow up their pads every night, but the trade-off is extra weight in their packs.
Sizes
Many pads come in normal, wide, long, or long-wide variations, depending on height. 25 inches is standard, and is how tent manufacturers calculate how they can market their tents. For example, if a tent it 50 inches wide, technically they can call it a 2 person tent, because they could fit two standard sleeping pads side by side, even though it wouldn't leave a single inch of extra room in between. Some sleeping pads are only designed to cover the torso. These smaller pads are used in ultralight backpacking, and the hiker will typically supplement another piece of gear underneath their legs, such as their pack or extra clothing that they are not wearing.
