An approximate calculation or rough estimate — a ballpark figure rather than a precise value (can be used with 'suru').
工事費は概算で三百万円程度になるだろう。
The construction cost will be roughly three million yen.
詳細設計が終わる前に概算見積を出してください。
Please provide a rough estimate before the detailed design is completed.
概算で時間を伝えておくと予定が立てやすい。
Giving an approximate time makes scheduling easier.