How do I calculate percentage increase?
Use the formula: ((New Value - Original Value) / Original Value) × 100. For example, from 100 to 125 is a 25% increase.
How do I calculate a discount?
Multiply the original price by the discount percentage (as a decimal). Subtract that from the original price. Example: 30% off $100 = $100 - $30 = $70.
What is percentage difference vs percentage change?
Percentage change compares to a starting value (old→new). Percentage difference compares two values without a 'starting point' — used when neither value is the 'original'.
How much should I tip?
In the US, 15-20% is standard for good service. 18% is the most common tip percentage. Our tip calculator lets you adjust and split the bill.
How do I calculate percentage of a number?
Multiply the number by the percentage expressed as a decimal. For example, 15% of 200 = 200 × 0.15 = 30. Alternatively, divide by 100 first (200 ÷ 100 = 2) then multiply by the percentage (2 × 15 = 30). This calculator does the math instantly and shows the work.
What's the difference between percentage change and percentage difference?
Percentage change compares a new value to an original value, using the original as the base. Percentage difference compares two values without a clear reference point, using their average as the base. Use percentage change for 'before and after' scenarios (like price changes). Use percentage difference when comparing two equally valid measurements.
Why does a 20% increase followed by a 20% decrease not return to the original?
Because the base changes. If you start with $100, a 20% increase gives $120. But 20% of $120 is $24, so a 20% decrease brings it to $96, not $100. The increase uses $100 as the base while the decrease uses $120. This asymmetry is important in finance — a 50% loss requires a 100% gain to recover.
How do I calculate a discount percentage?
Find the difference between original and sale price, then divide by the original price and multiply by 100. Example: original $80, sale $60 → savings $20 → (20 ÷ 80) × 100 = 25% discount. This calculator handles it automatically — just enter both prices.