10mm vs 13mm Lifting Belt: Which Thickness Do You Need?

What the extra 3mm changes

Belt thickness is the depth of the leather in millimetres, measured along the main length of the belt. Keep the leather and the width the same and change only the thickness. The amount of leather rises 30%, in step with the thickness. Resistance to bending does not rise in step: for a flat strip it scales with the cube of the thickness, so a 13mm belt is about 2.2 times as hard to fold as a 10mm one.

What the model does not tell you is how much more support the thicker leather gives. We found no study that has measured it, or that compares belt thicknesses, and the closest comparison we found, a 1990 squat study of six lifters using a light and a heavy belt, found little difference between them. What the model does explain is why 13mm feels so different, because folding is what you feel.

You feel it at the bottom of a squat, where your torso shortens and the belt has to bend with it. You feel it on a conventional deadlift, where the front edge meets your hip crease. And you feel it during break-in, because breaking a belt in is the process of teaching it to fold to your shape.

Why 10mm suits most women

10mm leather is already very stiff. Against a hard brace it barely moves, and we found no evidence that going thicker adds weight to the bar.

A shorter torso makes the folding penalty worse. If your rib-to-hip gap is small, the belt spends more of each rep bent, and a belt that resists bending more than twice as hard on the model is less willing to sit in that gap. If your seated rib-to-hip gap is under about 8.5 inches, our size chart's 3-inch threshold, sort out height before you think about thickness.

Break-in is shorter. Because it bends more easily, a 10mm belt conforms to your shape sooner than a 13mm one.

It is usually cheaper. Comparing lever with lever on our shortlist, the 10mm Inzer starts at $99 and the 13mm SBD at $190, though part of that gap is brand rather than thickness. The table below has the full list, with one 13mm belt on it. Closure is a separate choice, covered in lever vs prong belts.

Who 13mm is for

• Lifters who compete and want the firmest belt their rules allow, after a full training block in a broken-in 10mm belt. In the IPF, 13mm is the maximum thickness along the main length of the belt, so it is the most rigid option the rules allow.
• Lifters with a long torso. If the belt rarely has to fold, the extra bending stiffness costs you little.

Neither the IPF nor USAPL requires 13mm. The IPF sets a maximum, not a minimum, and USAPL's 2026 rulebook sets no thickness limit at all.

10mm and 13mm side by side

• Leather: 13mm has 30% more, and weighs more in proportion.
• Resistance to folding, on the model: 13mm is about 2.2 times 10mm.
• Break-in: 10mm conforms sooner, because it bends more easily.
• IPF status: both are legal from an approved manufacturer; 13mm is the limit.
• USAPL status: both are legal; there is no thickness limit.
• Lever-to-lever price on our shortlist: 10mm Inzer from $99, 13mm SBD from $190.
• Options on our shortlist: three 10mm leather belts and one 13mm.

What about deadlifts?

On the model, the folding penalty should show up most on conventional deadlifts. At the start position the front of the belt presses into the crease between your torso and thighs, and a stiffer belt presses harder. Some lifters who squat in 13mm pull in something thinner, or wear their belt a hole looser to pull.

Sumo lifters keep a more upright torso, which leaves more room at the front. There is more on this in belts for deadlifts.

Thickness on a nylon belt

Nylon belts are not measured the same way. Their stiffness depends on the webbing, the foam or plastic insert and the buckle, so a thickness figure on a nylon belt is not comparable to leather. If you are deciding between materials rather than thicknesses, see leather vs nylon lifting belts.