Back-of-the-envelope calculation

/bˈakɒvðɪˈɛnvəlˌəʊp kˌalkjʊlˈeɪʃən/

/bˈækʌvðɪˈɑːnvəlˌoʊp kˌælkjʊlˈeɪʃən/

[noun]

[NOUN]

a rough estimate or calculation done quickly and informally, often using basic methods or assumptions

Examples

1. A quick back-of-the-envelope calculation reveals the 5.8 US dollars per hour saved would be just marginally worthwhile for the average business traveler, but not for the average leisure traveler.

2. And this is just a very simple back-of-the-envelope calculation type of way of estimating the cost of a solar system.

3. Could we figure out a good value for B by doing a back-of-the-envelope calculation?

4. They do some back-of-the-envelope calculations regarding the distance between the planets and conclude that Trelane is about 900 years behind Earth history.