Overall sizes are measured in inches by waist and inseam- just like jeans.
However, overalls have to go over your belly. So if your belly hangs over the top of your jeans, you may need a much bigger waist size in overalls.
This is because your waist size in overalls will be the widest part of your belly.
So to get an accurate idea of your waist size, take a measuring tape and measure around the biggest part of your belly. Add 2-6 inches to that number for comfort.
Also known as "length". This is usually the same size you wear in jeans.
Plan on your overalls shrinking about an inch in length after the first few washes. For example, from a 32" inseam to 31".
To keep your buckles lasting as long as possible, be sure to buckle them before placing them in the laundry.