Math

Mathematical and statistical calculators

Angle Converter

Convert between SI and historical plane-angle units (radian, milliradian, degree, gradian, turn, arcminute, arcsecond) anchored to the BIPM SI Brochure definition of the radian.

Area Converter

Convert between metric and imperial area units (square millimetre, square centimetre, square metre, hectare, square kilometre, square inch, square foot, square yard, acre, square mile) with NIST-grade exact factors.

Energy Converter

Convert between SI, electrical, and thermal energy units (joule, kilojoule, megajoule, watt-hour, kilowatt-hour, thermochemical calorie, IT calorie, kilocalorie, BTU, US therm, electronvolt) with NIST-grade exact factors anchored to the 2019 SI redefinition.

Force Converter

Convert between SI, gravitational, and CGS force units (newton, kilonewton, dyne, kilogram-force, tonne-force, pound-force, ounce-force, short-ton-force) with NIST-grade exact factors anchored to CGPM 1901 standard gravity.

Length Converter

Convert between metric, imperial, and astronomical length units (millimetre, metre, kilometre, inch, foot, yard, mile, nautical mile, ångström, light-year, AU, parsec) with NIST-grade exact factors.

Mass Converter

Convert mass between metric (kg, g, mg, tonne), avoirdupois (lb, oz, stone, short ton, long ton), troy ounce, grain, and the metric carat with NIST-grade exact factors.

Percentage Calculator

Calculate percentages instantly: find X% of a number, or what percentage one number is of another.

Power Converter

Convert between SI and historical power units (watt, kilowatt, megawatt, mechanical horsepower, metric horsepower / PS, electric horsepower, BTU per hour, kilocalorie per hour, foot-pound per second). Disambiguates the three horsepower variants that vary by hundreds of watts.

Pressure Converter

Convert between SI, atmospheric, and gravitational pressure units (pascal, kilopascal, megapascal, bar, millibar, atmosphere, torr, mmHg, psi, kgf/cm², inH2O, cmH2O) with NIST-grade exact factors and conventional liquid-column values.

Roman Numerals Converter

Convert numbers to Roman numerals and back, instantly. Bidirectional, with a place-value breakdown, a date-to-Roman tattoo mode, and support up to 3,999,999.

Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur temperatures. Handles non-multiplicative scales correctly using the SI offset definition (0 °C = 273.15 K exactly, 13th CGPM 1967).

Time Converter

Convert time between nanoseconds, microseconds, milliseconds, seconds, minutes, hours, days, weeks, fortnights, months, years, and decades. Exact SI factors, honest Julian month and year conventions.

Torque Converter

Convert between SI and imperial torque units (newton-metre, kilonewton-metre, kilogram-force metre, kilogram-force centimetre, pound-foot, pound-inch, ounce-inch) with NIST-grade exact factors anchored to CGPM 1901 standard gravity and the 1959 international yard and pound.

Unit Converter

Convert between length, mass, volume, area, temperature, pressure, energy, power, force, torque, angle, time, and data storage units with NIST-grade exact factors.

Volume Converter

Convert between metric, US customary, and UK imperial volume units (millilitre, cubic centimetre, litre, cubic metre, cubic inch, cubic foot, cubic yard, US fluid ounce, US pint, US gallon, UK pint, UK gallon) with NIST-grade exact factors.

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Indonesian

IPK Calculator (Indonesia)

Calculate your Indonesian IPK (Indeks Prestasi Kumulatif) from course grades and SKS credits. Supports the Dikti grading system with predikat classifications (Cum Laude, Sangat Memuaskan, Memuaskan).

Malay

Malaysian CGPA Calculator

Calculate your Malaysian CGPA on the 4.0 scale from course grades and credit hours. Matches the MOHE grading system used by Malaysian public and private universities.

Thai

Thai GPA Calculator

Calculate your Thai GPA on the 4.0 scale from course grades and credits. Works for Thai university and secondary school students, including semester and cumulative GPA.

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Math Calculators

Free math calculators for everyday and academic use. From percentages and fractions to statistics and algebra, these tools give you instant, accurate results without the hassle of manual calculations.

Our math calculator collection is growing — we're building more tools to help students, professionals, and anyone who needs quick math answers.

Percentages

The percentage calculator handles the three most common percentage questions in one tool: find X% of a number, determine what percentage one number is of another, and calculate the percentage change between two values. All calculations happen in real time as you type — no buttons needed.

Whether you're calculating tips, grades, discounts, or growth rates, the percentage calculator gives you the answer instantly.

Your Math Toolkit

Our math calculators are designed to save you time on calculations that come up in school, work, and daily life. Each tool provides instant, accurate results so you can focus on what matters — understanding the numbers.

Have a suggestion for a math calculator you'd find useful? We're always looking to add tools that make math easier.

Frequently Asked Questions

How do I calculate a percentage of a number?

Use the percentage calculator and enter the percentage and the number. For example, to find 15% of 200, enter 15 and 200. The result (30) appears instantly. The formula is: result = number × (percentage / 100).

How do I find what percentage one number is of another?

Use the "X is what % of Y?" section. Enter the part (X) and the whole (Y). For example, if 30 is the part and 200 is the whole, the result is 15%. The formula is: percentage = (part / whole) × 100.

How do I calculate percentage change?

Use the percentage change section. Enter the original value and the new value. The calculator shows whether it's an increase or decrease and by what percentage. The formula is: change = ((new - old) / |old|) × 100.

Are these calculators free to use?

Yes, all our calculators are completely free with no sign-up required. Just open the tool you need, enter your numbers, and get instant results.