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Calculadora Capital

Percentage Calculator

Percentages are behind almost every money decision: interest, VAT, income tax, discounts, raises and margins. This calculator solves the four everyday percentage sums: how much a percentage of a value is, what percentage one value is of another, the change between two values, and how to increase or decrease a value by a percentage. For example, 20% of 100 is 20.

Pick what you want to work out and fill in the two fields. The same calculator does percentages, discounts and increases. For example, 20% of 100 is 20.

Result
20

Educational estimate, not financial advice. It calculates percentages; for VAT, income tax or interest, use the dedicated calculators.

What is a percentage of a value

This is the most common sum: to find X% of a value, divide the percentage by 100 and multiply by the value (X ÷ 100 × value). 20% of 100 is 0.20 × 100 = 20; 23% of €1,500 (Portugal’s standard VAT rate) is €345. It is the same sum you use for VAT, a commission or a tip.

What percentage one value is of another

To find what percentage the part is of the total, divide the part by the total and multiply by 100 (part ÷ total × 100). If you saved €20 on an €80 purchase, you saved 20 ÷ 80 × 100 = 25%. It tells you what share of your budget a cost is, or how big a saving is relative to your salary.

The percentage change between two values

Change measures how much a value rose or fell, in percent: (ending value − starting value) ÷ starting value × 100. From €100 to €125 is a +25% rise; from €200 to €150, a −25% fall. This is how you read inflation, a pay rise or an investment’s return.

Increase or decrease a value by a percentage

To apply a rise or a discount, add or subtract the percentage of the value: increasing is value × (1 + X ÷ 100), decreasing is value × (1 − X ÷ 100). A 30% discount on €80 leaves €56; a 23% rise on €1,000 gives €1,230. Choose “Decrease” for a discount and “Increase” for a price or salary rise.

Worked example

Take an €80 jumper with 30% off. In the “Increase or decrease a value” mode, with value 80, percentage 30 and “Decrease”, the calculator shows €56 (the discount is €24). To check what percentage you saved against the full price, the “What percentage one value is of another” mode with 24 and 80 confirms the 30%. And going from €56 back to €80 would need a rise of about +42.9%, not 30%, because the base changed.

Frequently asked questions

How do you calculate a percentage of a value?
Divide the percentage by 100 and multiply by the value: X% of a value = X ÷ 100 × value. For example, 20% of 100 is 0.20 × 100 = 20. The calculator does it for you in the “What is a percentage of a value” mode.
How do I know what percentage one value is of another?
Divide the part by the total and multiply by 100: part ÷ total × 100. If 20 is the part and 80 the total, 20 ÷ 80 × 100 = 25%. Use the “What percentage one value is of another” mode.
How do you calculate the percentage change between two values?
The change is (ending value − starting value) ÷ starting value × 100. From 100 to 125 the change is +25%; from 200 to 150 it is −25%. A positive sign is a rise, a negative one is a fall.
How do I calculate a discount?
A discount is a percentage decrease: value × (1 − discount ÷ 100). A 30% discount on €80 leaves 80 × 0.70 = €56. In the “Increase or decrease a value” mode, choose “Decrease”.
Why does removing and re-adding the same percentage not give the original value?
Because the base changes. A 30% discount on €80 gives €56, but to get from €56 back to €80 you need a rise of about 42.9%, not 30%, since 30% of €56 is less than 30% of €80. It is the same reason a 50% fall then needs a 100% rise to recover.

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Author: Thorben Rasmus Idel · Reviewed by: Nahar Geva · Last reviewed: 2026-06-24