PureTools
Percentage Calculator
Calculate percentages instantly across six modes, increase, decrease, % of, difference, reverse, change. Live results, visual progress bar, locale-aware formatting. Free and entirely private.
Percentage Increase
Calculate the result after adding a percentage to a value.
Percentage Decrease
Calculate the result after subtracting a percentage from a value.
Percentage of a Number
Calculate what a given percentage represents of a number.
Percentage Difference
Symmetric difference between two values, relative to their average.
Reverse Percentage
Find the original value before a percentage was applied.
Percentage Change
Directional change between an old (reference) and new value.
How to use the Percentage Calculator
- Pick a mode from the tabs at the top, Increase, Decrease, % Of, Difference, Reverse %, or % Change.
- Enter your two values. Results update live as you type. The visual progress bar at the bottom gives you a quick at-a-glance feel for the magnitude.
- For Reverse %, also pick whether the price was increased or decreased by the given percentage, this changes the formula.
- Click Copy summary to put a clean text recap on your clipboard, or Reset to clear all fields.
Common percentage formulas
- Increase: New = Original × (1 + p / 100)
- Decrease: New = Original × (1 − p / 100)
- % of a number: Result = Number × p / 100
- % difference (symmetric): p = |V1 − V2| / ((V1 + V2) / 2) × 100
- % change (directional): p = (New − Old) / Old × 100
- Reverse % (after increase): Original = Final / (1 + p / 100)
- Reverse % (after decrease): Original = Final / (1 − p / 100)
Real-world examples
- Sales & discounts: A $80 jacket marked 25% off costs $60, you save $20.
- Salary raise: A $3,000 monthly salary with a 5% raise becomes $3,150.
- Tax extraction: A $120 receipt including 20% VAT means a pre-tax price of $100 (Reverse mode, "increased by").
- Tip: A $50 dinner with 18% tip totals $59, the tip itself is $9.
- Inflation & growth: Prices going from $100 to $110 represent a 10% increase (% Change mode).
Frequently asked questions
How do I calculate a percentage increase?
Multiply the original value by (1 + percentage / 100). For example, a 20% increase on $100 gives $100 × 1.20 = $120, with an increase amount of $20. The Increase mode of this tool does this calculation for you and shows both the new total and the absolute increase. When the same rate compounds repeatedly over time, see the Compound Interest Calculator.
How do I calculate a discount or sale price?
Multiply the original price by (1 − percentage / 100). For example, 25% off $80 gives $80 × 0.75 = $60, with $20 saved. The Decrease mode shows both the discounted total and the savings amount in real time. Enter the original price as the base value, the discount as the percentage, and use the result as the amount saved or subtract it from the original price.
What is the difference between Difference and Change modes?
Percentage Difference is symmetric: it compares two values without picking a reference, using their average as the divisor, useful in science when neither value is the "before". Percentage Change is directional: it always uses the old value as the reference, so it tells you how much something has grown or shrunk relative to its starting point.
What is reverse percentage and when is it useful?
Reverse percentage finds the original amount before a percentage was applied. If a price increased by 20% to $120, the original was $120 ÷ 1.20 = $100. If a price decreased by 20% to $80, the original was $80 ÷ 0.80 = $100. This is essential for tax calculations (extracting the pre-tax price), for finding the price before a discount, or for confirming retail markup.
Why are very large or very small numbers shown differently?
To stay readable, numbers below 0.01 or above one billion automatically switch to scientific notation. Numbers in the normal range get thousands separators and up to two decimal places. This avoids displaying thirty-digit floating-point artifacts while preserving precision when it matters. Scientific notation prevents long strings of digits from overflowing cards on mobile while still preserving the scale needed for comparison and checking.
How do I find what percentage one number is of another?
Switch to the % Of tab, enter the percentage in the first field and the base number in the second. The result is the raw amount that percentage represents. A common example: 30% of 250 gives 75. The same mode applies to commissions, markups, budget allocations and tipping, whenever you need an absolute amount rather than a ratio or a directional change between two values.
Can I use this for tip and tax calculations?
Yes. For tips, use the Increase mode: enter the bill amount and the tip percentage to see the total and the tip amount separately. For reverse tax, finding the pre-tax price from a tax-inclusive total, use the Reverse % mode with "was increased by" and enter the tax rate. This works for VAT at 20%, GST at 10%, a 15% service charge or any other percentage-based markup. The result shows both the original amount and the difference in one step.