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Percentage Calculator

Calculate a percent of a number, a share of a total, percentage change, or the original value before a discount or markup.

Inputs

Choose the calculation mode, enter the base amount, and provide either a percentage or a part depending on your goal.

Decide if you need a percentage (part ÷ base) or a value (base × percent).

Starting amount that the percent or part references (price, salary, total, etc.).

Used for percent-of and reverse calculations. A reverse decrease must be below 100%.

Result

Shows the main result for the selected calculation mode

Value of percentage
25

Displayed when the calculator is set to return the amount created by a percentage of the base.

Analysis & guidance

  • Compare scenarios

    Toggle between modes with different inputs to test quotes, taxes, savings, or commissions.

  • Copy-friendly

    Only the requested number is shown, making it easy to reuse elsewhere.

  • Reality check

    Convert parts back to percent to confirm that invoices and fees match what was promised.

Frequently asked questions

What’s the difference between percent and percentage points?

Percent is a relative change, while percentage points describe an absolute difference between two percentages. For example, from 20% to 25% is +5 percentage points, which is a 25% relative increase.

How do I calculate a discount or a markup?

Use “Value of percentage” to compute a percent of a base (for example 25% of 800). For discounts, subtract that value from the base. For markups, add it.

Why doesn’t +20% and then −20% return to the original?

Because the base changes. After a 20% increase, the new base is higher, so a 20% decrease removes more in absolute terms. To undo a 20% increase, you need a 16.67% decrease.

How is rounding handled?

Percent results often produce decimals. For money or invoices, you typically round to two decimals, but for analysis you may want more precision.

Value of a percentage

Select this mode when you know the base amount and the percent you want to apply. Perfect for discounts, VAT, commissions, or margins where you only need the resulting amount.

Percentage of a value

Pick this direction when you know the base and the portion. The tool instantly shows what percentage that portion equals so you can verify invoices or budgets.

No extra clutter

Each calculation returns a single, focused result so you can copy it directly into your spreadsheet, chat, or note without additional cleanup.

Four worked percentage examples

25% of 800 is 800 × 0.25 = 200. If 200 is part of 800, its share is 200 ÷ 800 × 100 = 25%. An increase from 800 to 1,000 is (1,000 − 800) ÷ 800 × 100 = 25%. If a price after a 20% discount is 800, the original price was 800 ÷ 0.80 = 1,000.

Percentages: the essentials

Percentages show a value “per 100”. They’re used everywhere: discounts, interest rates, tax rates, and growth.

Basic formulas

  • Percentage of a number: value = base * (percent / 100)
  • Percent change: changePercent = (new - old) / old * 100
  • Before an increase: original = final / (1 + percent / 100)
  • Before a decrease or discount: original = final / (1 - percent / 100)

Percentage points vs percent

These two are easy to mix up:

  • Going from 20% to 25% is +5 percentage points.
  • Relative change is +25% (because 5 is 25% of 20).

Discounts and markups

A common surprise:

  • Increase by 20% and then decrease by 20% does not return to the start.

Example:

  • Start 100 → +20% = 120
  • 120 → −20% = 96

Rounding

For money, rounding to whole currency units is often fine. For rates, one or two decimals can be more informative.

Use the calculator to explore scenarios quickly and avoid manual mistakes.

How to read this calculator

These results are meant as guidance. They are based on rules, assumptions, and simplified models that can differ from your exact real-world situation.

Estimate, not a legal decision

Use the result as decision support and planning help. For high-stakes choices, confirm the details with the relevant authority, lender, employer, or adviser.

Methodology

Each calculator uses defined inputs, assumptions, and logic. We explain the broader approach on the methodology page.

Read methodology

Sources and updates

Important calculators should be traceable back to official rules, public guidance, or other clearly stated references.

Read about sources

Continue calculating

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