rough calculation
nounUK /rʌf ˌkælkjʊˈleɪʃən/
US /rʌf ˌkælkjəˈleɪʃən/
A quick guess using easy numbers to get an answer that is close but not exact.
I did a rough calculation and figured the trip would take about three hours.
RELATED WORDS
OTHER MEANINGS
2. An approximate result reached by rounding numbers to make the math easier.
By rounding to the nearest ten, her rough calculation gave 200 instead of 187.
3. A first quick pass at a problem before doing the exact work.
The engineer made a rough calculation to check whether the design was even possible.
4. An informal judgment of cost or amount made without exact measurements.
A rough calculation of the groceries put the bill at around forty dollars.