Hey Biswa,
Look what I have found!!!
Men's Underwear Fitting guide - Men's Underwear Sizing Information
Men's Sizing Charts
[TABLE="class: tbl, width: 480"]
[TR]
[TD="colspan: 3, align: center"]Fit Chart[/TD]
[/TR]
[TR]
[TD]T-Shirts[/TD]
[TD]Contoured[/TD]
[TD]Form-fitting through the shoulders, chest and sides.[/TD]
[/TR]
[TR]
[TD]Regular[/TD]
[TD]Fitted through the shoulders, chest and sides.[/TD]
[/TR]
[TR]
[TD]Full/Relaxed[/TD]
[TD]Loose through the shoulders, chest and sides.[/TD]
[/TR]
[TR]
[TD]Oversized/Athletic[/TD]
[TD]Very loose through the shoulders, chest and sides.[/TD]
[/TR]
[TR]
[TD]Underwear[/TD]
[TD]Contoured[/TD]
[TD]Form-fitting, meant to hug the body; usually a
stretch knit fabric.[/TD]
[/TR]
[TR]
[TD]Relaxed[/TD]
[TD]More loose fitting; usually a woven cotton fabric.[/TD]
[/TR]
[/TABLE]
[TABLE="class: tbl, width: 480"]
[TR]
[TD="colspan: 9, align: center"]Men's Underwear Sizes[/TD]
[/TR]
[TR]
[TD]Size[/TD]
[TD="align: center"]S[/TD]
[TD="align: center"]M[/TD]
[TD="align: center"]L[/TD]
[TD="align: center"]XL[/TD]
[TD="align: center"]XXL[/TD]
[TD="align: center"]3XL[/TD]
[TD="align: center"]4XL[/TD]
[TD="align: center"]5XL[/TD]
[/TR]
[TR]
[TD]Waist [/TD]
[TD="align: center"]28"-30"[/TD]
[TD="align: center"]32"-34"[/TD]
[TD="align: center"]36"-38"[/TD]
[TD="align: center"]40"-42"[/TD]
[TD="align: center"]44"-46"[/TD]
[TD="align: center"]48"-50"[/TD]
[TD="align: center"]52"-54"[/TD]
[TD="align: center"]56"-68"
[/TD]
[/TR]
[/TABLE]
Unlike Mr Prasad, I don't think I would be in such a chivalrous mood with a sales woman!