back-of-the-envelope

Adjective

idiomatic

(idiomatic) Approximate, rough, simplified, especially of a calculation, estimation or other reasoning.

Japanese Meaning

大雑把な概算（おおざっぱな計算や推定）を行う様子を表す表現。 / 概算、ざっくりとした推定や計算のこと

Before committing resources, we ran a back-of-the-envelope calculation to see if the timeline was feasible.

リソースを投入する前に、スケジュールが現実的かどうかを確かめるために概算の計算を行いました。

Sense（1）

(idiomatic) Approximate, rough, simplified, especially of a calculation, estimation or other reasoning.

Do some back-of-the-envelope calculations before all the facts come in.