Parts, increases and reversals
Finding 15 % of a price is not the same task as calculating the percentage change between two prices. The percentage tools distinguish a share of a total, a rise or fall, and the final amount after a discount.
Free tools
Math
The math category focuses on compact calculations that often interrupt an exercise, an invoice check or a day-to-day comparison. Percentage, percentage change, rule of three, fractions, averages, ratios, scientific notation and probability do not follow one single pattern. A shop discount, a weighted grade, a recipe proportion and the chance of an event each require a different setup. The pages show the operation, the order of the inputs and the meaning of the result so the arithmetic step can be reviewed without hiding the reasoning.
Linked quantities
Ratios and rule-of-three problems appear when two measurements move together. They help scale ingredients, split workloads, convert speeds or check whether an amount grows in proportion to another value.
Exact fractions versus decimals
Fractions preserve structure, while decimals make comparison easier. The fraction calculator keeps both readings visible when an exact expression is useful but an approximate number is needed for interpretation.
Grades and grouped values
An average can be misleading when coefficients or outliers matter. Math pages dealing with means and grades show how each value enters the total rather than presenting a single isolated score.
Probability and extreme numbers
Probability counts favourable outcomes inside a defined set. Scientific notation compresses values that are too large or too small for comfortable reading, which makes the order of magnitude easier to check.
Frequently asked questions
Why can a percentage decrease not simply undo the same increase?
A 20 % increase from 100 creates 120. Returning from 120 to 100 requires a 16.67 % decrease because the second percentage is applied to the new base.
What is the main difference between a ratio and an average?
A ratio compares two related quantities such as distance per hour. An average summarises a set of values, so it may hide how those values relate to another measurement.
Should fractions always be converted before comparing results?
No. A fraction can keep an exact value that a decimal rounds away. Decimal form is useful for quick ranking, but exact form is often better in algebra or school exercises.
Tools to explore
Percentage Calculator
Quick and precise calculations for margins, changes, and ratios.
Rule of Three
Solve for variables through direct mathematical proportion.
Fraction Calculator
Add, subtract, multiply and divide fractions with a simplified result.
Ratio Calculator
Compare two quantities, simplify A:B, convert the ratio to percentages and scale it to a real total.
Average Calculator
Calculate a simple or weighted average, inspect coefficients, median, spread, contribution and distribution charts.
Percentage Change Calculator
Calculate an increase, decrease, absolute delta, multiplier and target gap between an initial and final value.
Discount Calculator
Calculate a final price after discount, promo code, tax, fees and quantity, then compare real savings scenarios.
Tip Calculator
Calculate a tip, taxes, fees, total with tip and per-person share for restaurants, delivery or shared bills.
Scientific Notation Converter
Convert numbers between standard, scientific and engineering notation with mantissa, exponent and significant digits.
Probability Calculator
Calculate simple, conditional, union, intersection and complement probabilities with fractions, percentages, odds and expected frequency.