How to Calculate Percentage in Excel: 4 everyday cases

Every percentage in Excel is a division followed by the % format. Four cases cover nearly everything.

Case 1: marks out of a total

1. Marks in B1 (72), total in B2 (80).
2. Click B3. Type =B1/B2. Enter.
3. Press Ctrl + Shift + %. Shows 90%.

Case 2: each item’s share of the whole

Values in A2:A6. In B2: =A2/SUM($A$2:$A$6). Format as %, drag down. The column adds to 100%.

Case 3: increase or decrease

Last year in A2, this year in B2:

=(B2-A2)/A2

Negative means a decrease.

Case 4: a discount or a tax

=A2*(1-15%)     → price minus 15%
=A2*(1+18%)     → price plus 18% GST
=A2*15%         → just the discount amount

Check it worked

72 out of 80 is 90. Half of anything is 50%. If you see 9000% you multiplied by 100 and formatted — do one or the other.

Common mistakes

#DIV/0! — dividing by an empty or zero cell. Wrap in IFERROR.

Decimals showing as 0%. Increase decimal places with the .00→ button on the Home tab.

More detail: percentage formula.