Write to support@shippingmath.com. ShippingMath is run by Harsh Parmar, and every message is read personally.
Reporting a calculation issue
Please include the carrier, service, destination country, the package measurements and weight you entered, and a link to the public rule or rate document you are comparing against.
Please protect customer privacy. Never send names, addresses, tracking numbers, invoices or unredacted order exports when reporting a calculator issue.