FinanceCalcs
Percentage Calculator
Five ways to calculate percentages — all on one page. Find what percent one number is of another, calculate percentage change, increase or decrease a value by a percentage, and more.
Works for discounts, tax calculations, test scores, investment returns, and any everyday percentage problem.
calculate What is X% of Y?
help_outline X is what % of Y?
trending_up Percentage Change (from → to)
add_circle_outline Increase / Decrease a Number by %
compare_arrows Percentage Difference between Two Values
lightbulb Quick Tips
10% trick: Move the decimal one place left. 10% of $85 = $8.50.
5% trick: Find 10%, then halve it. 5% of $80 = $4.00.
20% trick: Find 10%, then double it. 20% of $65 = $13.00.
Change vs. Difference: % change has a direction (increase or decrease). % difference is symmetric — it doesn't care which value came first.
"Not everything that counts can be counted, and not everything that can be counted counts."
— Often attributed to Albert Einstein
What is a percentage calculator?
A percentage is a way of expressing a number as a fraction of 100 — the word comes from the Latin per centum, meaning "by the hundred." Percentages appear in nearly every area of daily finance: taxes, discounts, investment returns, test scores, tips, and more.
Percentage change measures how much a value has increased or decreased relative to its starting point. One important quirk: a 50% increase followed by a 50% decrease does not return to the original — it results in a 25% net loss, because each percentage is calculated on a different base.
Percentage difference compares two values symmetrically — neither is treated as the reference point. It is used when there is no natural "before" and "after," such as comparing two prices side by side.
lightbulb Example Percentage Scenarios
Discount: A $120 item is 25% off. The sale price is $120 × (1 − 0.25) = $90. You save $30.
Sales tax: An 8% tax on a $65 purchase adds $5.20, for a total of $70.20.
Test score: You got 43 out of 50 questions correct. That is 43 ÷ 50 × 100 = 86%.
Investment return: A portfolio grew from $10,000 to $13,500. That is a percentage change of ($13,500 − $10,000) ÷ $10,000 × 100 = +35%.
Many people use a percentage calculator to quickly verify discounts, check tax totals, and calculate returns without doing the mental math by hand.
Percentage Calculator FAQs
What is the difference between percentage change and percentage difference?
Percentage change has a direction — it measures how much a value increased or decreased from a specific starting point. Percentage difference is symmetric — it compares two values without treating either as the baseline. Use percentage change for before/after comparisons, and percentage difference when comparing two equal-standing values.
Why doesn't a 50% increase followed by a 50% decrease return to the original?
Because each percentage is applied to a different number. A 50% increase on $100 gives $150. A 50% decrease on $150 gives $75 — not $100. Percentage gains and losses are always calculated on the current value, not the original, which is why they are not symmetrical.
How do I calculate what percentage one number is of another?
Divide the part by the whole, then multiply by 100. For example, 15 is what percent of 60? 15 ÷ 60 × 100 = 25%. Calculator #2 above solves this instantly for any two numbers.
How do I increase or decrease a number by a percentage?
To increase: multiply the number by (1 + the percentage as a decimal). To decrease: multiply by (1 − the percentage as a decimal). For example, to increase $80 by 15%: $80 × 1.15 = $92. To decrease $80 by 15%: $80 × 0.85 = $68. Calculators #4 and #5 above handle both.
Percentage terminology
Percentage
A ratio expressed as a fraction of 100. Written with a % symbol. 75% means 75 out of every 100, or 0.75 as a decimal.
Percentage Change
The relative change between an old value and a new value: ((new − old) ÷ old) × 100. Positive results indicate an increase; negative results indicate a decrease.
Percentage Difference
A symmetric comparison between two values using their average as the denominator: (|value1 − value2| ÷ ((value1 + value2) ÷ 2)) × 100. Neither value is treated as the reference point.
Base Value
The reference number a percentage is calculated from. In percentage change, this is the original or starting value. Misidentifying the base is a common source of percentage errors.
Percentage Point
The arithmetic difference between two percentages. If an interest rate rises from 3% to 5%, that is an increase of 2 percentage points — not a 2% increase (which would mean a 6% rate).
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