How is percentage change calculated?

Change = ((Y − X) / X) × 100. A positive result is an increase, a negative one a decrease. It is always relative to the starting value X.

Why is the percentage increase larger than the decrease for the same numbers?

Because the base differs: going from 80 to 100 is a 25% increase (base 80), but 100 to 80 is a 20% decrease (base 100). Percentages depend on the reference value.

It is (X / 100) × Y. For example, 15% of 200 is 30. This is the calculation behind discounts, tips and tax amounts.

How is percentage change calculated?

Change = ((Y − X) ÷ X) × 100, always relative to the starting value X. A positive result is an increase, a negative one a decrease. The base matters: the same gap gives different percentages depending on which value is the starting point.

It is (X ÷ 100) × Y. For example, 15% of 200 is 30. This is the calculation behind discounts, tips, tax amounts and any "a share of a total" question.

Finance Calculators

Percentage Calculator

Percentages are everywhere — discounts, taxes, raises, statistics — and the three questions in this calculator cover most of them: a percentage of a value, what percentage one value is of another, and the percentage change between two values.

Enter two values, X and Y. The calculator answers all three questions at once so you do not have to pick a mode.

Keep it bookmarked for the everyday percentage sums — a discount at the till, a raise at work, a tax rate — that are easy to get wrong by eye.

Value X

Value Y

Enter your values to see the result.

How this is calculated

This calculator answers the three percentage questions people meet most often, all at once from two values X and Y. First, X% of Y is (X ÷ 100) × Y — the calculation behind discounts, tips and tax amounts. Second, X is what percent of Y is (X ÷ Y) × 100 — used to express one value as a share of another. Third, the percentage change from X to Y is ((Y − X) ÷ X) × 100 — the basis of raises, growth rates and price changes.

Percentage change is always relative to the starting value X, which is why the same gap produces a bigger percentage when the base is smaller. Going from 80 to 100 is a 25% increase (base 80), but 100 down to 80 is a 20% decrease (base 100).

The model is direct arithmetic with no assumptions. It does not distinguish percentage change from percentage-point change (a rate rising from 10% to 12% is a 2-point increase but a 20% relative increase), and it does not handle compound growth over multiple periods — use the compound interest or inflation calculators for those.

Worked example

X = 25, Y = 200.

125% of 200 = (25 ÷ 100) × 200 = 50.
225 is what % of 200 = (25 ÷ 200) × 100 = 12.5%.
3Change from 25 to 200 = ((200 − 25) ÷ 25) × 100 = 700%.

Frequently asked questions

How is percentage change calculated?: Change = ((Y − X) / X) × 100. A positive result is an increase, a negative one a decrease. It is always relative to the starting value X.
Why is the percentage increase larger than the decrease for the same numbers?: Because the base differs: going from 80 to 100 is a 25% increase (base 80), but 100 to 80 is a 20% decrease (base 100). Percentages depend on the reference value.
What is X% of Y?: It is (X / 100) × Y. For example, 15% of 200 is 30. This is the calculation behind discounts, tips and tax amounts.
How is percentage change calculated?: Change = ((Y − X) ÷ X) × 100, always relative to the starting value X. A positive result is an increase, a negative one a decrease. The base matters: the same gap gives different percentages depending on which value is the starting point.
What is X% of Y?: It is (X ÷ 100) × Y. For example, 15% of 200 is 30. This is the calculation behind discounts, tips, tax amounts and any "a share of a total" question.

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Method: direct percentage arithmetic. No external data source. Last updated: September 2026.

These results are indicative estimates for planning only and do not constitute financial advice. Actual loan terms, tax rules, investment returns and product conditions vary by country, provider and your personal circumstances. Always confirm figures with your bank, tax authority or a qualified financial adviser before making decisions.