It’s no secret that sleeping on the ground can get cold - and a sleeping bag alone often isn’t enough. That is because over time the insulation beneath you gets compressed under your body weight, reducing its ability to retain heat. That's where a sleeping pad comes in.
Sleeping pads are rated using an R-value, which means how well they resist transfer. The higher the R-value, the better the pad will insulate you from the cold ground and keep you warm throughout the night.