# Back-of-the-envelope calculation

## Metaphor for a rough calculation / From Wikipedia, the free encyclopedia

#### Dear Wikiwand AI, let's keep it short by simply answering these key questions:

Can you list the top facts and stats about Back-of-the-envelope calculation?

Summarize this article for a 10 years old

SHOW ALL QUESTIONS

A **back-of-the-envelope calculation** is a rough calculation, typically jotted down on any available scrap of paper such as an envelope. It is more than a guess but less than an accurate calculation or mathematical proof. The defining characteristic of back-of-the-envelope calculations is the use of simplified assumptions.

Metaphor for a rough calculation

A similar phrase in the U.S. is "back of a napkin", also used in the business world to describe sketching out a quick, rough idea of a business or product.[1] In British English, a similar idiom is "back of a fag packet".