Discount & sales tax
Stack two discounts, add a tax rate, and see the final price and actual saving.
Everyday moneyEveryday money
Percentage toolkit calculator
Percentages without the head-scratching.
Your numbers
Calculate a percentage, compare two numbers, or increase and decrease an amount.
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THE MATH, WITHOUT THE MYSTERY
What’s actually happening here?
A percentage is a fraction out of 100. Multiplying by 0.15 finds 15%; dividing by 100 converts a percentage to a decimal.
For percentage change we use the absolute original value as the denominator. That gives an intuitive direction when the starting value is negative. A change from zero is undefined, not an infinite or 100% increase.
THE FORMULA
X% of A = A × X/100; Change = (B − A) / |A| × 100
A small example
15% of 200 is 30. Increasing 200 by 15% gives 230. Moving from 200 to 250 is a 25% increase.
GOOD QUESTIONS
A few things worth knowing.
Are percentage points the same as percent?
No. A rate moving from 10% to 15% rises by 5 percentage points, but by 50% relative to its original rate.
Why will a 20% rise and 20% fall not cancel?
They use different bases. Starting at 100, a 20% rise gives 120; a 20% fall from 120 gives 96.