I once tried to use a cheap scale for estimating shipping.
The constant results were that I either ate the excess costs
or I had to send change back to the buyer.
With four kids at home, I just can't afford the outrageous
price for a "postal scale."
Most of them are stupidly expensive and, moreover,
limited to small packages.
If you have had this problem, go to your nearest "Sam's Club"
and look in the office supplies section.
There is a digital scale branded "Royal"- comes in a red box.
It will weigh packages from less than a pound up to 350 pounds.
It costs $48 here in Dallas. I've been weighing stuff with it
for a few months and it's spot-on with the Post Office.
One caution: it is not rugged. It handles normal shipping
chores without problems, but don't throw it on the floor
and keep it away from the kids.
Jumping on and off it to watch the numbers wink
will mean another trip to Sam's and another $48.

73 Dave S.