When our customers come in store they are often surprised at the number of different widths of belts we offer. The fact is that we start at thin 15mm width belts and go all the way upto 60mm width belts, most of the time in 5mm increments with each width having its own specific purpose.
Luckily for men life is not as complex as it is for women - there are really just 3 widths to focus on and each have their own raison d'etre. I'll give you a brief guide to what I think works best and hope that this will help you in the process of choosing your next belt.
For me the 30mm width belt has two purposes - first and foremost it falls into the category of formal. For those occasions when you really want something slim and discreet this is the width for you. Most of the men's belts in this width as a result are fairly simple in style with a focus on elegant leather and occasionally some subtle detail.
In the past a lot of men considered this the default width to go to for a formal belt, irrespective of their waist size and build. I would beg to differ as I often feel that it looks a little too thin on anyone of a certain size and stature. In reality a belt of this width on a larger man, let's say 34" waist or above, just tends to look a little mean. If you are perhaps a few pounds heavier than your perfect weight this can also exacerbate things, with the belt looking like it is cutting into your stomach. In which case head for the 35mm width.
Which brings me to the second category - the 30mm belt as a more trendy item. This for me is really all about the stature and clothing style of the person wearing it. If you are on the slim side, like slimmer cut trousers and suits, then this width will look good on you. This could either be in a formal capacity or a more trendy capacity with the use of colour and texture.
The 35mm width is one which I believe to be the default width to turn to for men's classic or casual wear. This width works very nicely with formal wear and the buckle collection that goes with it has plenty of discreet options to choose from. My preference for this width is predominantly guided by most men's size and stature. The average man is a 34-36" waist size and I just like the way this width of belt looks on a man. It looks substantial without being chunky, it has the nice feeling when worn of properly supporting your trousers and filling the belt loops and also, because of its width means the belt buckle is just that little wider which I feel suits most men better.
In terms of detailing, if you are looking for something a little more contemporary then this width is also a suitably sized canvas to show off some subtle style - perforations, shoe inspired detailing, brush off leathers....
Which leads me onto the more casual nature of this width and its versatility. Although I would not advocate this width as the perfect width for jeans, it is a width that can easily cross the boundary between formal and casual. The width is substantial enough to not look out of place on denim or heavier fabric trousers (e.g. corduroy), and looks great on chino style trousers, so your belt can cross nicely from work to play. I particularly like this width for smart denim, especially of the more fitted nature.
The 40mm width is one that many people are just not aware of. In truth if you go shopping you will not find any particular choice in this width other than perhaps the odd simple jeans belt. The reality is that this is the perfect width for wearing with your jeans and with nearly all casual trousers. Worn with denim not only does it nicely fill the deep belt loops but also most importantly the width both looks and feels in keeping with the style and weight of the fabric. The same applies for almost all casual trousers as nowadays these also tend to have fairly deep loops. Above all we just like the way a 40mm width belt feels around the waist - it is substantial without being chunky, really shows off the texture of the leather and any specific style detailing and gives you scope to wear either a classic or more substantial buckle style.
Obviously the type of leather in this width will define how smart or casual the belt is - a chunky unlined leather inherently is for more informal wear whereas perhaps a finer grain leather would be more suitable for smarter occasions.
Personally, and subject to my comment above on the type of leather, I use this width for almost all but the most formal of occasions - it is really versatile, a great canvas for all sorts of buckles and also importantly gives that really nice feeling of a belt that is properly holding up your trousers.