Choose calculation type. Enter values. Get result instantly. Multiple calculation types.
Percentages constant—discounts, tips, grades, returns. Never memorize formulas.
Four core types: X% of Y (find a percentage of a number), what % is X of Y (find the ratio), percent change (increase or decrease between two values), and reverse percentage (find the original number before a known percent change). Switch modes from the top of the calculator.
Enter the original value and the new value. The calculator returns the percent increase (positive) or decrease (negative) using the formula ((New − Original) / Original) × 100. Useful for price changes, salary raises, weight loss, and stock returns.
Yes. Decimals like 17.5% or 0.0825 are handled to full precision — no rounding until the final display. For financial calculations, the underlying math is double-precision, so a 0.001% difference won't compound into a measurable error.
((New − Original) / Original) × 100. If the result is positive, the new value is larger by that percent; if negative, smaller. Note: a 50% increase followed by a 50% decrease does NOT return to the original — it ends at 75% of the original (asymmetric by design).
The Toolzie Percentage Calculator handles all common percentage problems: find what percent X is of Y, calculate percentage increase or decrease, find the original value before a percentage change, and more.
Select 'What percent is X of Y?', enter 25 for X and 200 for Y. The answer is 12.5%.
Enter 85 as the original value and 15 as the percentage. The tip amount is $12.75.
Select 'Percentage change', enter the original value and the new value — the calculator shows the percentage increase or decrease.
Select 'Original value from percentage', enter the final value and the percentage off to find the original price.
Estimates only. Not tax, financial, or legal advice. Full disclaimer · Terms