How are you?
Back-of-a-napkin (or back-of-a-fag-packet (BrE)) is an expression used to describe something was calculated / measured in a rough way without precision; an estimation.
The technical term is back-of-the-envelope calculation.
- It represents the idea is that you just grabbed any old piece of paper, a napkin, for example, to jot / write down your ideas.
- (business) - to describe the action of sketching out a quick, rough idea of a business or product.
- to estimate = to try to judge something without calculating.
I've done some back-of-a-fag-packet calculations and I think this product can make a good profit.
Eu fiz alguns cálculos por cima / estimados / em esboço / em rascunho e acho que este produto pode gerar um bom lucro.
(1) ROAM, Dan. The Back of the Napkin - Solving Problems and Selling Idead with Pictures. Portfolio Publisher. 2013.
(2) AUSTIN, B.A. Precursors To Radar — The Watson-Watt Memorandum And The Daventry Experiment. International Journal of Electrical Engineering Education. 1999.
(3) STIRLING, Bruce. Business Idioms in America. Nova Press. 2012.