Belt Finishing:  

To Determine the Belt Size and Stitching Area:

• Measure a belt that fits from end of the buckle (including the buckle) to the hole most often used.  OR
• Take Pant Size and add 2 inches (38" pants would be 40" Belt Size).
• Stitch 4 inches less than the Belt Size - which will allow for the leather to be added during finishing
• Leave 1.5 to 2 inches on each end to be attached to the leather during finishing.  

For 38" Pants, Belt Size would be 40.  Stitch area would be 36 - leaving 2 inches at each end for finishing

The sides of the belt will need to be bound with a binding stitch.  There are examples of this stitch on You Tube.  

I have had difficulty finding the leather for finishing.  However, 

https://jet.com

sells a belt for $5.00 which you could purchase for the leather buckle and tab.  The name of the product is:  Small Mens Fabric with Leather Tabs Casual Golf Belt.