Percentage Calculator

What this calculator does

The Percentage Calculator is fourteen separate calculations behind one set of tabs. Each tab has its own inputs and its own formula, because “percentage” covers several genuinely different operations that people frequently mix up.

The fourteen modes are: % of Number, What % Is, % Change, % Increase, % Decrease, Discount, Reverse %, % Difference, Remaining %, Points Diff, Tip Calculator, Markup, Profit & Loss and Grade %.

Every result comes with the formula and the same formula with your numbers substituted into it, so you can see the arithmetic rather than just the answer. COPY RESULT and COPY FORMULA copy either one; ☆ SAVE keeps a calculation in your browser's local storage alongside a recent-history list.

How to use it

1. Pick the tab that matches your questionThis is the step that decides whether the answer is right. “What is 20% of 500?” is % of Number; “100 became 125, by what percent?” is % Change; “I paid 90 after 10% off, what was the list price?” is Reverse %.
2. Enter the valuesDecimals are accepted throughout, and negative percentages are valid in the change and increase/decrease modes. Empty or non-numeric input produces a clear error rather than a wrong number.
3. Press CALCULATEThe result appears with the formula above it and your values substituted below it. If a mode cannot produce an answer — dividing by a zero total, for instance — it says so instead of showing a misleading figure.
4. Read the substitution line, not just the numberThe substitution is what tells you the tool interpreted your question the way you meant it. If the substituted formula does not look like what you intended to ask, you are on the wrong tab.
5. Copy or save what you needCOPY RESULT gives the answer, COPY FORMULA gives the working, and ☆ SAVE stores the calculation locally for reuse. History and favourites are held in your browser and nowhere else.

What the results mean

% of Number and What % Is are inverses

The first answers “what is X% of Y” and returns a quantity; the second answers “X is what percentage of Y” and returns a percentage. If the number you get back is in the wrong kind of unit, you have used the wrong one.

Percentage change versus percentage difference

Change is directional and measured against the original value: ((New − Original) ÷ Original) × 100, so it can be negative. Difference is symmetric and measured against the average of the two values, so it has no direction and swapping the inputs gives the same answer.

Increase and decrease return the new total

These modes give you the final value, not the size of the change. 200 increased by 15% returns 230, not 30.

Reverse % undoes a percentage

Dividing by the factor is what reverses a percentage, and this is where most manual attempts go wrong. A price of 90 after a 10% discount was 100, because 90 ÷ 0.90 = 100 — not 99, which is what adding 10% back would give.

Percentage points are not percent

The Points Diff mode reports both: the absolute gap in points and the relative change. A rate moving from 4% to 5% is 1 percentage point, and also a 25% increase. Both statements are true and they mean different things.

The formula

These are the expressions the calculator evaluates, written out so you can reproduce any result by hand.

Worked example

Limits worth knowing

A browser can only report what the platform gives it. These are the honest boundaries of this page, so a result is never read as more than it is.

• It is arithmetic, not advice. The tool computes exactly what you ask; deciding which percentage question to ask is the part it cannot do for you.
• Results are subject to ordinary floating-point rounding, the same as any calculator or spreadsheet. The engine formats output rather than carrying unlimited precision, so a long recurring decimal will be shown rounded.
• Nothing is sent anywhere. History, favourites and settings live in your browser's local storage, and clearing that storage removes them permanently.
• Percentage change is undefined when the original value is zero — there is nothing to compare against — and the tool reports that rather than returning infinity.

Tips

• When a result surprises you, read the substitution line first. Nine times out of ten it shows you asked a slightly different question than you meant.
• For anything involving two successive percentages — a discount then tax, or two discounts in a row — use the Discount Calculator's successive-discount section rather than adding the percentages together.
• Save the calculations you repeat. Favourites keep the inputs as well as the expression, so a recurring markup or tip calculation is one click away.

Troubleshooting

Related documentation

• CalculatorDiscount CalculatorSale price, savings, successive discounts, reverse discount and offer comparison.
• CalculatorGST CalculatorAdd or remove GST, with CGST, SGST and IGST split and Indian number formatting.
• CalculatorScientific CalculatorTrigonometry, logs, factorials and statistics with a zero-eval expression parser.
• CalculatorSalary CalculatorCTC to in-hand salary with New and Old regime tax, PF, professional tax and gratuity.
• CalculatorBMI CalculatorBody Mass Index in metric or imperial, with the healthy weight range for your height.