What Percentage Calculator helps you do

Handle five common percentage questions in one place: a percent of a number, a percentage change, one number as a percent of another, and an increase or decrease by a percent. It saves choosing the right formula each time. In change mode, Value A is the new figure and Value B is the original.

Calculations run in your browser and no values are sent to Haivix.

How it works

These are everyday arithmetic calculators: a percentage, a tip split, a body-mass index and a loan installment. Each one applies a fixed formula to the numbers you type and updates as you edit; nothing is looked up and nothing is sent to a server. The display rounds to a couple of decimals, but the calculation itself keeps full precision until the final formatting step. Because the formulas are simple, the assumptions around them matter more than the arithmetic: whether a tip is calculated before or after tax, whether a BMI scale fits the person, and whether a loan uses reducing balance or a flat markup.

How to use Percentage Calculator

Pick the percentage operation you need.
Enter the two values, checking which one is the base.
Read the result and the detail line.
Copy the value into your document or spreadsheet.

When to use it

Work out a discount or a tax amount.
Find the percentage change between two figures.
Express one number as a percentage of another.
Apply a price increase or markdown.
Check a quoted growth rate against two values.
Convert a fraction into a percentage for a report.

When not to use it

Do not use it to chain percentage changes; compounding needs a different calculation.
Do not confuse percentage points with percent change.
Do not treat a percent change as symmetric; a rise and a fall of the same size differ.

Example

15% of 200 is 30. Going from 200 to 250 is a 25% increase, while going from 250 to 200 is a 20% decrease. 50 is 25% of 200. Increasing 200 by 10% gives 220, and decreasing it by 10% gives 180. Dividing by zero shows a dash instead of a number.

What you can do with Percentage Calculator

Calculate X percent of Y.
Calculate the percent change from B to A.
Express A as a percent of B.
Increase A by B percent.
Decrease A by B percent.
Show results to two decimals.

Example: check the assumption, not just the arithmetic

Confirm the units before trusting the number. Kilograms versus pounds and centimeters versus inches change a BMI completely.

Check what the percentage is taken from. A percentage of the bill, of the pre-tax total and of the post-tax total are three different amounts.

Round only at the end. Rounding a tip or an installment early can shift the total by more than a cent.

Read the result in context. A BMI category is a screening band, not a diagnosis, and a monthly payment says nothing about the total cost.

Do not treat a general-purpose calculator as medical, tax or financial advice.

Decide how the result should be rounded for its use. A tip may round up to the next note, while an installment is usually fixed by the lender's own rounding rule.

Check the direction of a change. A rise from A to B and a fall from B to A are different percentages, even though the amounts are the same.

What to know before you start

It handles the standard operations and does not chain multiple percentage changes with compounding.
Rounding is applied to the displayed result, which may differ slightly from exact math.
Change mode always treats A as the new value and B as the old value.
It does not distinguish percentage points from percent change.

Common mistakes

Swapping the base in change mode.
Treating a 20% drop as reversible by a 20% rise.
Adding two percentage changes without compounding.
Reading a percentage point difference as a percent change.

Troubleshooting

If the result is a dash, the base value in that mode is zero.

If change looks inverted, swap A and B.

If the answer has trailing zeros, the display rounds to two decimals.

If the percentage is over 100, check which value is the base.

Percentage Calculator