Mathematical calculators123 calculators
Updated on June 14, 2026
Convert speed between metric, imperial, and nautical units — metres per second, kilometres per hour, miles per hour, feet per second, and knots.
Calculate the speed of sound in dry air from the air temperature — v = 331.3 + 0.606 × T (T in °C), about 343 m/s at 20 °C.
Calculate average speed in km/h and pace in minutes per kilometre from a distance in kilometres and a time in hours.
Calculate the volume and surface area of a sphere from its radius using V = 4/3 × π × r³ and A = 4 × π × r².
Calculate the volume, curved surface area, and base radius of a spherical cap from the sphere radius and cap height — volume = (πh²/3)(3R−h), curved surface = 2πRh, base radius = √(h(2R−h)).
Calculate the elastic potential energy (PE = ½kx²) in joules stored in a stretched or compressed spring from its spring constant and displacement.
Calculate the total square footage of a rectangular area from its length and width, with the result shown in square feet and square metres.
Find the capacity of a cylindrical, rectangular, or capsule tank in litres, US gallons, imperial gallons, and cubic metres.
Convert temperature between Celsius, Fahrenheit, and Kelvin — instantly and with exact, offset-based scale definitions.
Calculate your test grade as a percentage and a US A–F letter grade from the points you earned out of the total possible points.
Solve the thin-lens equation (1/f = 1/dₒ + 1/dᵢ) for the image distance and magnification from a focal length and object distance.
Convert torque between newton-metre, pound-foot, pound-inch, kilogram-force metre, and more — instantly and with exact, newton-metre-based conversion factors.
Calculate the volume and surface area of a torus (a donut) from its major radius R and minor radius r — volume = 2π²Rr², surface area = 4π²Rr.
Calculate the secondary voltage of an ideal transformer from its turns ratio — Vs = Vp × (Ns ÷ Np), in volts (V).
Calculate the area of a trapezoid (UK: trapezium) from its two parallel sides and the perpendicular height — area = ((a + b) / 2) × h.
Calculate the area of any triangle from its base and perpendicular height using the formula area = ½ × base × height.
Calculate the output voltage of a two-resistor voltage divider — Vout = Vin × R₂ ÷ (R₁ + R₂), in volts (V).
Convert volume between metric, US customary, and UK imperial units — millilitres, centilitres, litres, cubic metres, US teaspoons, tablespoons, fluid ounces, cups, pints, quarts, US gallons, and UK gallons.
Calculate the wavelength and period of an electromagnetic wave from its frequency — wavelength = c ÷ f and period = 1 ÷ f.
Convert weight (mass) between metric and imperial units — milligrams, grams, kilograms, metric tonnes, ounces, pounds, and stone.
Calculate your weighted grade average in percent — give each grade a share, all shares should add up to 100%. Dynamically supports 2–8 grades.
Estimate how many pages your word count fills for common font sizes and line spacings, with single- and double-spaced results shown clearly.
Calculate the mechanical work done by a force over a distance — work = force × distance × cos(θ), measured in joules.