How do I calculate percentage decrease?

Subtract the new value from the old one, divide by the old value and multiply by 100. From 250 to 200: (250 − 200) ÷ 250 × 100 = 20%.

How do I reduce a number by a percentage?

Multiply it by 1 minus the percentage as a decimal. To take 15% off 60, calculate 60 × 0.85 = 51.

Why is a 50% increase followed by a 50% decrease not a return to the start?

The decrease applies to the larger number. 100 up 50% is 150, and 150 down 50% is 75.

Can percentage decrease be negative?

A negative result means the value went up. This calculator reports it as an increase so the sign is never ambiguous.

Percentage Decrease Calculator

Find the percentage decrease between two numbers, or reduce a number by a percentage.

Updated September 19, 2026Checked by the editorial team

Original value

New value

Percentage decrease

25%

(90 − 120) ÷ 120 × 100 = -30 ÷ 120 × 100

A percentage decrease shows how much smaller a new number is compared with the original. It applies to falling prices, weight loss, shrinking budgets and dropping traffic.

Enter an old and a new value to find the decrease, or enter a starting number and a percentage to see what is left after the reduction.

How percentage decrease calculator works

In the first mode the calculator finds the drop between the two values and expresses it as a share of the original. If the new number is higher, it says so and switches to an increase.

In the second mode you supply a number and a percentage to remove. You get the reduced value and the amount taken off.

The formula

% decrease  =  (Old − New) ÷ Old × 100
New value  =  Old × (1 − Percentage ÷ 100)

As with any percentage change, the original value is the base.

Worked example: a weekly budget cut from 250 to 200

Drop: 250 − 200 = 50.

Divide by the original: 50 ÷ 250 = 0.20.

The decrease is 20%.

Check it: 250 × (1 − 0.20) = 200.

When to use this tool

Measuring how far a price has fallen from its high.
Tracking a drop in website visits, sales or subscribers between months.
Working out the weight or spending you have cut relative to where you started.
Finding the sale price after a set percentage comes off.

Common mistakes to avoid

Using the new value as the base. A fall from 250 to 200 is 20% of 250, not 25% of 200.
Expecting two successive 10% cuts to equal a 20% cut. They equal 19%, because the second applies to a smaller number.
Quoting a decrease above 100%. A quantity cannot fall by more than all of itself, so a result over 100% means an input is wrong.

Frequently asked questions

How do I calculate percentage decrease?: Subtract the new value from the old one, divide by the old value and multiply by 100. From 250 to 200: (250 − 200) ÷ 250 × 100 = 20%.
How do I reduce a number by a percentage?: Multiply it by 1 minus the percentage as a decimal. To take 15% off 60, calculate 60 × 0.85 = 51.
Why is a 50% increase followed by a 50% decrease not a return to the start?: The decrease applies to the larger number. 100 up 50% is 150, and 150 down 50% is 75.
Can percentage decrease be negative?: A negative result means the value went up. This calculator reports it as an increase so the sign is never ambiguous.

Learn more

Results are for information only and are not financial, legal or medical advice. The calculation logic is covered by automated tests, and examples on this page are worked out and re-checked before publishing. Spotted a mistake? Tell us.