Math & Conversions
Percentages, fractions, unit conversions · 42 tools
Fractions 1
Geometry 8
Circle Calculator Circle area, circumference, and diameter from the radius — instant, any unit.
-> Cylinder Calculator Cylinder volume, lateral and total surface area from radius and height — tanks, cans, pipes.
-> Ellipse Calculator Ellipse area, Ramanujan circumference, eccentricity, and focal distance from the two semi-axes.
-> Pythagorean Theorem Calculator Hypotenuse from two legs via a²+b²=c² — diagonals, ramps, and square corners, with area and perimeter.
-> Quadratic Equation Solver Solve ax²+bx+c=0 instantly: discriminant and both real roots via the quadratic formula.
-> Slope Calculator Slope, y-intercept, and distance from two points — the full y = mx + b workup, instant.
-> Sphere Calculator Sphere volume, surface area, diameter, and circumference from the radius — any unit.
-> Triangle Area Calculator Area of any triangle from three sides via Heron's formula — plus perimeter, instant.
-> Numbers 2
Percentages 11
Birthday Paradox Calculator The probability two people share a birthday in any group — why 23 people is already a coin flip.
-> Confidence Interval Calculator Confidence interval and margin of error from mean, SD, and sample size at 90/95/99% levels.
-> Exponent Calculator Raise any number to any power — negative and fractional exponents included, with the reciprocal shown.
-> Logarithm Calculator All three logarithms of any number: base 10, natural, and base 2 — instant and precise.
-> Lottery Odds Calculator Your real jackpot odds, the coin-flip equivalent, and the absurd ticket count a 50% chance would take.
-> P-value Calculator Turn a z-score into one- and two-tailed p-values using the standard normal distribution.
-> Percent Error Calculator Percent error for lab reports: absolute difference over the accepted value, times 100.
-> Percentage Calculator Three common percentage questions: X% of Y, X is what percent of Y, and percent change from A to B.
-> Proportion Calculator Solve A:B = C:X by cross-multiplication — recipes, map scales, prices, and any direct proportion.
-> Square Root Calculator Square root, cube root, square, and cube of any number — live as you type.
-> Z-Score Calculator Z-score and approximate percentile from value, mean, and standard deviation — the standard score explained.
-> Statistics 8
Bayes' Theorem Calculator Positive and negative predictive value from prevalence, sensitivity, and specificity — the base-rate math everyone gets wrong.
-> Combination & Permutation Calculator Combinations, permutations, repetition variants, and factorials with exact big-integer math — no rounding, ever.
-> Critical Value Calculator z and t critical values for any significance level, one- or two-tailed, with rejection regions — matches standard tables.
-> Empirical Rule Calculator Turn a mean and standard deviation into the 68%, 95%, and 99.7% ranges of the normal distribution.
-> Margin of Error Calculator Margin of error from sample size, confidence level, and proportion — why 1,000 people means ±3.1 points.
-> Probability Calculator Combine independent probabilities: both, either, neither, and at-least-once-in-n-tries.
-> Sample Size Calculator Survey sample size from confidence level, margin of error, and population — with the finite-population correction.
-> Statistics Calculator Full descriptive statistics from pasted data: mean, median, mode, standard deviation, quartiles, IQR, five-number summary, and outliers.
-> Unit conversions 12
Angle Converter Convert angles between degrees, radians, gradians, turns, arcminutes, and arcseconds.
-> Area Converter Convert area between square meters, square feet, acres, hectares, and square kilometers.
-> Force Converter Convert force between newtons, pounds-force, kilograms-force, kilonewtons, and dynes.
-> Frequency Converter Convert frequency between hertz, kHz/MHz/GHz, RPM, and radians per second.
-> Length Converter Convert between metric and imperial length units — millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles — instantly in your browser.
-> Power Converter Convert power between watts, kilowatts, horsepower, PS, and BTU/h — engines, motors, and HVAC.
-> Pressure Converter Convert pressure between Pa, kPa, bar, PSI, atm, mmHg, and inHg — tires, weather, and lab units in one place.
-> Speed Converter Convert speed between mph, km/h, m/s, and knots instantly in your browser.
-> Temperature Converter Convert temperatures between Celsius, Fahrenheit, and Kelvin instantly — with the offset math that simple converters get wrong.
-> Torque Converter Convert torque between newton-metres, pound-feet, pound-inches, and kgf·m — wrench settings and engine specs.
-> Volume Converter Convert volume between liters, milliliters, US gallons, quarts, cups, and fluid ounces.
-> Weight Converter Convert weight and mass between kilograms, grams, pounds, ounces, and stone — instantly in your browser.
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