Free Online Math Calculators

About MathMint

MathMint provides free, fast, and accurate math calculators for students, teachers, and professionals. From basic percentage and fraction calculations to advanced statistics and geometry, our tools help you solve math problems instantly with step-by-step explanations and no sign-up required.

Percentages: The Most Practical Math Skill

Percentage calculations appear constantly in everyday life — discounts, interest rates, tip calculations, exam scores, and financial planning all rely on them. The fundamental percentage formula is: Percentage = (Part ÷ Whole) × 100. For reverse calculations: finding the original price before a 20% discount requires dividing by 0.8 (the complement), not subtracting 20% from the discounted price. Percentage change is calculated as: (New − Old) ÷ Old × 100. A common error is confusing percentage points with percentages: an interest rate rising from 5% to 7% is a 2 percentage-point increase but a 40% relative increase.

Algebra: Solving for the Unknown

Algebraic tools include quadratic equation solvers, linear equation systems, and factoring calculators. The quadratic formula x = (−b ± √(b² − 4ac)) ÷ 2a solves any equation in the form ax² + bx + c = 0. The discriminant (b² − 4ac) determines the nature of solutions: positive means two real solutions, zero means one repeated solution, and negative means two complex (imaginary) solutions. Systems of linear equations — two or more equations with two or more unknowns — are solved by substitution, elimination, or matrix methods. For 2×2 systems, Cramer's Rule provides a direct formula using determinants.

Statistics: Making Sense of Data

Descriptive statistics summarise a dataset's key features. The mean (average) is the sum divided by count; the median is the middle value when sorted; the mode is the most frequent value. Standard deviation measures spread around the mean — a low standard deviation indicates data points cluster close to the mean, while a high standard deviation indicates wide spread. For a normal distribution, approximately 68% of values fall within one standard deviation of the mean, 95% within two, and 99.7% within three (the 68-95-99.7 rule). These statistics form the foundation for hypothesis testing, confidence intervals, and regression analysis used across science, economics, and engineering.

Frequently Asked Questions

How do I calculate a percentage of a number?

To find a percentage of a number, multiply the number by the percentage and divide by 100. For example, 25% of 80 is (80 x 25) / 100 = 20. The percentage calculator handles this and three other common percentage operations: finding what percentage one number is of another, calculating percentage change between two values, and finding the original number before a percentage was applied.

What is a quadratic equation and how do I solve it?

A quadratic equation has the form ax² + bx + c = 0 where a, b, and c are constants and a is not zero. It can be solved using the quadratic formula: x = (-b ± √(b² - 4ac)) / 2a. The discriminant (b² - 4ac) tells you the type of solution: positive gives two real roots, zero gives one repeated root, and negative gives two complex roots. The quadratic solver computes all solutions and shows the step-by-step work.

What is standard deviation and when should I use it?

Standard deviation measures how spread out numbers are from the average (mean) of a dataset. A small standard deviation means values cluster tightly around the mean; a large one means they are widely dispersed. Use it when you need to understand data variability — comparing test scores, evaluating investment risk, or quality control in manufacturing. The standard deviation calculator computes both population and sample standard deviation along with variance and other summary statistics.

How do I convert fractions to decimals or percentages?

To convert a fraction to a decimal, divide the numerator by the denominator: 3/4 = 0.75. To convert to a percentage, multiply the decimal by 100: 0.75 x 100 = 75%. To go the other way, express the percentage as a fraction over 100 and simplify: 60% = 60/100 = 3/5. The fraction calculator performs addition, subtraction, multiplication, and division of fractions with automatic simplification.

Are the calculators accurate enough for academic work?

MathMint calculators use JavaScript's IEEE 754 double-precision floating-point arithmetic, which provides approximately 15-17 significant decimal digits of precision. This is more than sufficient for most academic assignments, homework verification, and professional calculations. For areas requiring arbitrary precision (e.g., cryptography or specific research applications), a specialized computer algebra system would be more appropriate. MathMint is designed for quick verification, concept checking, and building mathematical intuition.