If you are not using metric measurements, you are using incorrect measurements. Canada Post went metric in 1974 and any other system is approximate.
EBay is an American company and has imperial measures as the default. You have to look at the Options dropdown menu to switch to the correct measurements,
By the by, why are you taking your items to the PO for weighing? You can print out shipping labels at home through Paypal and get a discount of 5% to 18% on many package services. Letter rates still need stamps, but those can be purchased on eBay at a discount of 10-25%.
Labelled or stamped parcel do not need any more work by the PO clerk, they can be dropped into the nearest red post box. (My daughter uses the one right outside the local PO since one of the clerks is grumpy and insists on reweighing and measuring all parcels, even though she is just wasting time.)
