Buy the widest mat your pack tolerates, because a shoulder or an elbow off the edge is in contact with the ground and the mat’s rating no longer describes your night. Width is the dimension makers trim first to reach a headline weight, and it is the one people notice most.
What “regular” usually means
Most ranges offer a regular width and a wide version several centimetres broader, and the regular figure is set by weight targets rather than by bodies. That sounds like a trivial difference until you lie on it: the mat has to hold shoulders, hips and whichever arm ends up outside the sleeping bag.
Makers publish width as a single figure for rectangular mats and as two — shoulder and foot — for tapered or mummy-shaped ones. Where only one number appears on a tapered mat, it is normally the widest point.
Why width interacts with the rating
The warmth figure for a mat is its R-value, a measure of resistance to heat flow. Since ASTM F3340 gave the industry a common test, R-values from different makers can be compared directly, so check the figure is quoted against that standard rather than invented in-house.
But an R-value describes the mat, not the parts of you that are not on it. Ground contact bypasses the mat entirely, and no rating covers that. This is a fit question that decides whether the warmth specification applies at all.
Thickness answers a different question
Thickness is not width and does not substitute for it. It decides whether a side sleeper’s hip reaches the ground through a compressed mat, which is a separate failure from rolling off the edge. Read both.
Some mats address the edge problem with raised side rails or thicker outer chambers, which keep a sleeper centred without adding overall width. Where a maker describes that construction, it is worth reading against the plain width figure.
What width costs you
Every extra centimetre is grams and packed volume, and mats are among the bulkiest things in a rucksack. The trade is real: packed size against weight against width is the triangle this category lives in.
A closed-cell foam mat never punctures and never packs small; an air mat is light and noisy; a self-inflating mat is heavier and quieter. Width behaves differently in each — a foam mat’s width is fixed by the sheet it is cut from, while an inflatable’s is a design choice.
Check it against the tent
Two wide mats side by side need a tent floor wide enough for them, and tent floor widths are published in the tent’s specification rather than the mat’s. A pair of regular mats that fit becomes a pair of wide mats that ride up the walls, which is a comfortable mat and an uncomfortable night.
The short answer
Take your shoulder width lying down, add room for the arm that ends up outside, and buy at least that. If the choice is between a warmer narrow mat and a wider one, the wide mat is usually the better night, because the rating on the narrow one only applies to the parts of you that stay on it.
What people ask before buying
Does a wide mat fit inside a tent designed for two?
Not always. Take the tent's floor width from its specification and compare it against two mats side by side, remembering that a two-person tent floor is often narrower at the foot end than at the shoulders.
Is a tapered mat a false economy?
It depends where you sleep. A tapered cut saves weight at the feet, which most people can spare, but it also narrows exactly where a side sleeper's knees end up. Read the width at the shoulder and at the foot separately where both are published.
Last reviewed 6 September 2026