How to Decrease a Number by a Percentage
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Direct answer
To reduce a value by p percent, multiply it by 1 − p/100. The multiplier gives the amount that remains, not the amount removed.
Formula and method
New value = original × (1 − percentage ÷ 100)
This page must show the formula exactly as the calculator or worked method uses it. Inputs remain unrounded during the calculation; rounding applies only to the displayed answer unless a domain-specific rule requires otherwise.
Step-by-step calculation
- Convert the percentage to a decimal.
- Subtract that decimal from 1.
- Multiply the original by the remaining-value multiplier.
- Round only when the output unit requires it.
Worked examples
15% discount
$240 × (1 − 0.15) = $204; the reduction is $36.
Reduce a budget
$5,000 × 0.92 = $4,600 after an 8% cut.
Inventory shrink
1,250 × 0.97 = 1,212.5; a countable-unit policy must decide how to round.
Interpretation and edge cases
- Percentage off describes the reduction; percent of original describes what remains.
- For sequential reductions, apply each multiplier in order.
- Rounding counts can change the achieved percentage.
Frequently asked questions
What multiplier represents a 30% decrease?
0.70.
Is 20% off the same as multiplying by 0.20?
No. Multiply by 0.80; multiplying by 0.20 gives the amount equal to the discount rate.
Can I use this in Excel?
Yes: =A2*(1-B2) when B2 is formatted as a percentage.
Sources and transparency
The formulas and examples were evidence-checked on 2026-09-10. This is educational mathematical content. It does not replace a field-specific standard, accounting policy, laboratory method, contractual definition or professional judgment. CalculatorGeek should display a named human reviewer only after a real reviewer has completed and documented that review.
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