Microsoft Excel allows you to calculate different formulas. One such formula is the reduction of a number by a certain percentage. For the calculation, you need to remember that it is not simply multiplying the number by the per cent. If you do this, you just find the per cent of your value. To reduce the number by your percentage, you need to also subtract it from your original value. You can complete this with one formula.

Type your value in cell A1. For example, Type "50" in cell A1.

Type the percentage in cell A2. In the example, type "30%."

Type "=A1-(a1*a2)" in cell A3. In the example, you will get 35. This is because 30 per cent of 50 is 15, so then "50 minus 15 equals 35."