Percentage Increase Calculator

How to use the calculator

1. Pick a mode:
   • Percentage change: from an old value to a new one, such as last year's rent versus this year's.
   • Increase or decrease by a percent: a starting value plus or minus a percentage, such as a 3% raise.
   • Percent difference: two values compared on equal terms, such as two store prices.
2. Enter the values. Decimals and negative numbers are allowed. To decrease by a percent, type a negative percentage (−25).
3. Read the result. Change mode shows the percentage, the difference (new − old), increase or decrease, and the factor (new ÷ old). Apply mode shows the new value, the amount added or removed and the multiplier.

Formulas

The old value is the base, so it can't be zero: growth from nothing has no percentage. Dividing by the absolute value of the old value keeps the sign meaningful when the base is negative: going from −50 to −20 is an increase of 60%. The percent difference uses the average of the two values as its base, so swapping them gives the same answer. Results are not rounded internally.

Worked examples

1. A raise

Your salary goes from $45,000 to $48,600. The change is +8%, a difference of $3,600 and a factor of 1.08.

2. A price hike and a drop

A product rises from $3.49 to $4.19: an increase of about 20.06%. A subscription falling from $250 to $190 is a −24% change.

3. Applying a percentage

A $2,450 rent rising 3.5% becomes $2,535.75 (+$85.75). A $1,500 laptop at 25% off costs $1,125.

4. Up 20%, then down 20%

Start at 100 and add 20%: 120. Take 20% off 120 and you get 96, not 100, because the second percentage is taken from a bigger base. To get back from 120 to 100 you need a change of −16.67%.

5. Percent change vs. percent difference

From 40 to 60 is +50%; from 60 to 40 is −33.33%. The percent difference between 40 and 60 is 40% in either order.

Percent vs. percentage points

When the values are themselves percentages, keep two ideas apart. A rate that rises from 4% to 5% has gone up 1 percentage point, which is a 25% relative increase. Reports on interest rates, unemployment or tax rates usually quote the change in points; this calculator returns the relative change.

Percentage changes can't be added: +10% followed by +10% is +21%, not +20%. Multiply the factors instead (1.1 × 1.1). And a decrease can never exceed −100% for positive values, while an increase has no upper limit.