Percentage Calculator

To find X% of Y, convert the percentage to a decimal and multiply: Result = (X ÷ 100) × Y. For example, 15% of 2,000 = (15 ÷ 100) × 2,000 = 0.15 × 2,000 = 300.

This is the formula behind tips, discounts, sales tax, and commission calculations. A quick mental shortcut: 10% of any number is simply that number with the decimal point moved one place left, and you can scale up or down from there — 5% is half of 10%, 20% is double 10%, and so on.

To express one number as a percentage of another, divide the part by the whole and multiply by 100: Percent = (X ÷ Y) × 100. For example, if you scored 42 out of 50 on a test, your percentage is (42 ÷ 50) × 100 = 0.84 × 100 = 84%.

This form is common in grading, conversion-rate reporting, and any "share of total" question. Always double-check which number is the "part" and which is the "whole" — reversing them gives a very different, and usually nonsensical, answer.

Percentage change compares an old value to a new value: Percentage change = ((New − Old) ÷ Old) × 100. A positive result means an increase; a negative result means a decrease.

For example, if a product’s price rises from 2,000 to 2,300, the change is ((2,300 − 2,000) ÷ 2,000) × 100 = (300 ÷ 2,000) × 100 = 15%. To increase a value by a known percentage directly, multiply by (1 + percent ÷ 100); to decrease it, multiply by (1 − percent ÷ 100).

Stacked discounts do not add up the way they appear to. A 20% discount followed by an additional 10% discount is not a flat 30% off — it is equivalent to multiplying by 0.8 and then 0.9, giving a combined 28% discount, not 30%.

• A 50% increase followed by a 50% decrease does not return the original number, because the second change applies to a larger base.
• "Percentage points" and "percent" are not interchangeable — a rate moving from 10% to 12% is a 2 percentage-point rise, but a 20% relative increase.
• Always confirm the denominator behind any reported percentage (per session? per user? per order?) before comparing two figures.

Beyond simple discounts, percentages underpin interest rates, salary raises, inflation, and investment returns — situations where the base amount often changes from one period to the next. A 5% pay raise on a larger salary is worth more in absolute rupees than the same 5% on a smaller one, which is an easy but important distinction to keep in mind when comparing offers or negotiating.

When comparing a percentage-based fee (say, a 2% transaction charge) against a flat fee across different transaction sizes, running both numbers through a quick percentage calculation before committing can reveal which option is actually cheaper for your typical amount, since the crossover point between a flat fee and a percentage fee depends entirely on the size of the transaction.

For a restaurant bill tip or a GST add/remove step on an invoice, the Tip Calculator and Sales Tax Calculator apply the same percentage math in those specific contexts, while the Fraction Calculator is handy when a ratio is easier to think about as parts of a whole than as a percent.