PercentConverter

How to Calculate Percent Decrease

Learn how to find the percentage decrease from an original value to a lower new value, with formulas and practical examples.

Quick answer

Subtract the new value from the original value, divide the decrease by the original value, then multiply by 100.

Percent decrease = ((Original − New) ÷ Original) × 100

What is percent decrease?

Percent decrease describes how much a value has fallen compared with where it started. It expresses the amount of reduction as a percentage of the original value.

For example, if a price drops from $100 to $80, the decrease is $20. Since $20 is 20% of the original $100, the price decreased by 20%.

Percent decrease formula

Start with the original value and the new, lower value. Subtract the new value from the original value to find the amount of decrease.

Percent decrease formula Percent decrease = ((Original value − New value) ÷ Original value) × 100

The original value is the baseline, which is why it goes in the denominator. Do not divide by the new value.

Use the Percentage Decrease Calculator Calculate the amount and percentage of decrease instantly.

How to calculate percent decrease step by step

  1. Identify the original value and the new, lower value.
  2. Subtract the new value from the original value.
  3. Divide the decrease by the original value.
  4. Multiply the decimal result by 100.
  5. Add the percent sign.

Example: Decrease from 100 to 80

  1. Original value: 100
  2. New value: 80
  3. Find the decrease: 100 − 80 = 20
  4. Divide by the original: 20 ÷ 100 = 0.20
  5. Convert to a percentage: 0.20 × 100 = 20%

Answer: The value decreased by 20%.

Percent decrease examples

Example: A price falls from $75 to $60

  1. Find the decrease: $75 − $60 = $15
  2. Divide by the original price: $15 ÷ $75 = 0.20
  3. Convert to a percentage: 0.20 × 100 = 20%

Answer: The price decreased by 20%.

Example: Inventory drops from 500 units to 425 units

  1. Find the decrease: 500 − 425 = 75
  2. Divide by the original inventory: 75 ÷ 500 = 0.15
  3. Convert to a percentage: 0.15 × 100 = 15%

Answer: Inventory decreased by 15%.

Example: A value falls from 750 to 590

  1. Find the decrease: 750 − 590 = 160
  2. Divide by the original value: 160 ÷ 750 = 0.213333...
  3. Convert to a percentage: 0.213333... × 100 = 21.33%

Answer: The value decreased by about 21.33%.

Find a new value after a percentage decrease

If you know the original value and the percentage decrease, convert the percentage to a decimal and subtract it from one. Then multiply the original value by the result.

New value after a decrease New value = Original value × (1 − Percentage ÷ 100)

Example: Decrease 240 by 25%

  1. Convert 25% to a decimal: 0.25
  2. Subtract from one: 1 − 0.25 = 0.75
  3. Multiply: 240 × 0.75 = 180

Answer: Decreasing 240 by 25% gives 180.

Shortcut: To decrease an amount by 25%, multiply by 0.75. To decrease it by 10%, multiply by 0.90. The multiplier equals one minus the percentage written as a decimal.

Find the original value before a percentage decrease

If you know the new value after a decrease, divide by the decrease multiplier to work backward to the original value.

Original value before a decrease Original value = New value ÷ (1 − Percentage ÷ 100)

Example: A sale price is $72 after a 20% decrease

  1. Convert 20% to a decimal: 0.20
  2. Find the multiplier: 1 − 0.20 = 0.80
  3. Divide: $72 ÷ 0.80 = $90

Answer: The original price was $90.

Common percent decrease mistakes

Dividing by the new value

Use the original value as the denominator. For a decrease from $100 to $80, divide the $20 decrease by $100, not by $80.

Confusing a dollar decrease with a percentage decrease

A price that falls from $100 to $80 decreases by $20, but its percent decrease is 20%. The dollar amount and the relative percentage are different measures.

Using percent decrease when the value rose

If the new value is higher than the original value, use the percent increase formula instead.

Reversing a decrease by adding the same percentage

A 20% decrease followed by a 20% increase does not restore the starting value. Each percentage is calculated from a different base.

Important: A standard percent decrease calculation cannot use zero as the original value because division by zero is undefined. Describe a change from zero in absolute terms instead.

Frequently asked questions

How do I calculate a 10% decrease?

Multiply the original amount by 0.90. For example, a 10% decrease on $200 is $200 × 0.90 = $180.

What is the percent decrease from 50 to 40?

The decrease is 10. Divide 10 by the original 50, then multiply by 100: 10 ÷ 50 × 100 = 20%. The decrease is 20%.

How do I calculate the original price after a discount?

Divide the sale price by one minus the discount percentage as a decimal. For a 20% discount, divide the sale price by 0.80.

Can percent decrease be more than 100%?

For positive starting values, a decrease cannot be greater than 100% without the result going below zero. A decrease to zero is exactly a 100% decrease.

Is a discount the same as percent decrease?

A percentage discount is a common type of percent decrease. It reduces an original price by a stated percentage.

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