Calc FYI

Percentage Calculator

Calculate percentages, percentage change, and percentage of a number

Calculator

X% của Y là bao nhiêu?

Kết quả

Thay đổi phần trăm từ X đến Y

Thay đổi

%

X là bao nhiêu phần trăm của Y?

Phần trăm

%

Quick Presets

Tip

Discount

Tax

How to Use

  1. 1
    Choose a calculation type

    Select '% of a value', '% change', or 'what percent' depending on your question.

  2. 2
    Enter the values

    Type your numbers in the input fields; the result updates instantly with the formula shown.

  3. 3
    Read the result

    The answer is calculated as you type — copy it or try another calculation type.

About

Percentages are one of the most common calculations in everyday life. Whether you are figuring out a restaurant tip, applying a coupon discount, calculating sales tax, or analyzing year-over-year growth, understanding percentages is essential.

The word "percent" comes from the Latin "per centum," meaning "by the hundred." A percentage expresses a number as a fraction of 100. For example, 25% means 25 out of every 100, or one quarter. This simple concept underpins financial calculations, statistics, science, and data analysis.

This calculator covers the three fundamental percentage operations. "Percentage of a value" multiplies a number by a percentage (useful for tips, taxes, and discounts). "Percentage change" measures the relative difference between an old and new value (useful for tracking growth, inflation, or price changes). "What percentage" determines what fraction one number represents of another (useful for grades, statistics, and proportions).

All calculations run entirely in your browser with no data sent to any server. Results update in real time as you type, and the underlying formula is displayed so you can verify the math or learn the method.

Frequently Asked Questions

What is the difference between percentage and basis points?
A basis point is one hundredth of a percentage point (0.01%). So 1% equals 100 basis points. Basis points are used in finance to describe small interest rate changes. For example, if a mortgage rate rises from 6.50% to 6.75%, that is a 25 basis point increase, not a 0.25% increase (which would imply 0.25% of 6.50%).
How does compound percentage work?
Compound percentages apply each change to the result of the previous change, not the original value. A 10% increase followed by a 10% decrease does not return to the original: $100 × 1.10 = $110, then $110 × 0.90 = $99. The net effect is a 1% loss, not zero. This is why sequential percentage changes cannot simply be added or subtracted.
How do I reverse a percentage to find the original value?
If a value has been increased by X%, divide the final amount by (1 + X/100). For example, if a price after 20% tax is $120, the original price is $120 / 1.20 = $100. For a decrease of X%, divide by (1 − X/100). A $75 sale price after a 25% discount means the original was $75 / 0.75 = $100.
What is the difference between margin and markup?
Markup is the percentage added to cost to get the selling price: (Price − Cost) / Cost × 100. Margin is the percentage of the selling price that is profit: (Price − Cost) / Price × 100. A product bought for $60 and sold for $100 has a 66.7% markup but a 40% margin. Margin is always lower than markup for the same transaction.
What is the difference between 'percentage of' and 'percentage off'?
'Percentage of' calculates a portion of a value (e.g., 20% of $100 = $20). 'Percentage off' subtracts that portion from the original (e.g., 20% off $100 = $100 − $20 = $80). In formulas: 'X% of Y' = Y × X/100, while 'X% off Y' = Y × (1 − X/100). The discount calculator uses the 'off' formula.

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