New Calculators

Convert lumens to lux by dividing luminous flux by the area in square metres — find out how bright a room or surface will be from a given light source.

Convert lumens to watts by dividing luminous flux by efficacy (lm/W) — compare LED, CFL, halogen, and incandescent bulbs to find the right wattage for your target brightness.

Convert lux to foot-candles instantly — enter an illuminance reading in lux (lm/m²) and get the equivalent in foot-candles (lm/ft²), the US/imperial unit used in lighting standards and photometry.

Convert a decimal (base-10) whole number into binary, octal, and hexadecimal — the number systems used throughout computing.

Decompose any whole number from 2 to 1,000,000,000 into its unique prime factors in exponent form — for example 360 into 2^3 multiplied by 3^2 multiplied by 5.

Convert any whole number from 1 to 3999 into its standard Roman numeral, using the subtractive notation (IV, IX, XL, XC, CD, CM).

Convert watts to lumens by multiplying wattage by luminous efficacy (lm/W) — compare LED, CFL, halogen, and incandescent bulbs to estimate brightness from power consumption.

Convert a battery energy in watt-hours to charge capacity in milliamp-hours by dividing by the nominal voltage — useful for reading power-bank spec sheets and airline limit labels.

Calculate the absolute humidity (grams of water vapour per cubic metre of air) from the air temperature (°C) and relative humidity (%) using the standard meteorological approximation.

Calculate the alcohol by volume (ABV%) of your home brew from the original and final specific-gravity readings: ABV = (OG − FG) × 131.25.

Estimate the air conditioner cooling capacity (BTU per hour) you need from your room size, using the 20 BTU per square foot rule of thumb.

Calculate the density of dry air (kg/m³) from its absolute pressure and temperature using the ideal gas law, ρ = P / (R × T).

Calculate the atmospheric pressure at a given altitude with the barometric formula for the troposphere — enter a height in metres to get the pressure in pascals.

Convert amps and volts to watts instantly using Watt's law (P = V × I). Also computes resistance in ohms — handy for household circuits, EV charging, and electronics projects.

Calculate the angle between two 3D vectors from cosθ = (A·B) / (|A| |B|), with the result in degrees from 0 to 180.

Calculate angular acceleration (α = (ω₂ − ω₁) / t) in rad/s² from an initial and final angular velocity over a time interval.

Convert an ordinary frequency in hertz into the angular frequency ω = 2πf in radians per second.

Calculate the angular momentum (L = m·v·r) of a point mass moving in a circle, in kg·m²/s, from its mass, tangential speed, and radius.

Calculate the angular size (apparent size) of an object in radians and degrees from its physical size and distance using the small-angle approximation.

Calculate angular velocity (ω = 2π·f) in rad/s from a rotational frequency, plus the tangential speed at a given radius.

Calculate the area and arc lengths of an annular sector (a slice of a ring) from its inner radius, outer radius, and central angle in degrees.

Calculate the half-wave dipole and quarter-wave antenna length in metres from a frequency in MHz and a velocity factor (λ = c / f).

Calculate the apparent brightness (radiant flux) of a star or light source in W/m² from its luminosity and distance using the inverse-square law.

Calculate the arc length of a circle (s = 2πr·θ/360) and the area of the matching circular sector from a radius and a central angle in degrees.

Calculate the reaction rate constant k = A · exp(−Ea / (R · T)) from the pre-exponential factor, activation energy, and absolute temperature.

Calculate the average damage per hit when critical hits are factored in, from your base damage, crit chance, and crit multiplier.

Calculate the final bacterial population after binary fission (finalCount = initialCount × 2^generations) from a starting cell count and the number of doublings.

Calculate the bandwidth-delay product (BDP) of a network link from its bandwidth in Mbit/s and round-trip latency in ms — the data volume kept in flight and the ideal TCP window size.

Calculate the ideal banking angle of a curve (θ = arctan(v²/rg)) in degrees — the angle that needs no friction to hold a vehicle on the road at a given speed and radius.

Calculate the Base64-encoded size (ceil(n / 3) × 4 bytes) produced when you encode a given number of input bytes, including padding.

Calculate the ideal battery life of a device in hours and minutes from its battery capacity (mAh) and the current it draws (mA).

Calculate the posterior probability P(A|B) with Bayes' theorem from a prior P(A) and the two likelihoods P(B|A) and P(B|¬A).

Calculate the beat frequency (f_beat = |f₁ − f₂|) in hertz from two superimposed wave frequencies.

Convert any wind speed in km/h to the Beaufort force (0–12) and metres per second — the scale used in marine and weather forecasts worldwide.

Calculate the absorbance of light through a solution (A = ε·c·l) from the molar absorptivity, concentration, and path length.

Calculate the length of an open belt around two pulleys from the centre distance and the large and small pulley diameters.

Calculate the binomial probability P(X = k) = C(n, k) · pᵏ · (1 − p)^(n − k) — the chance of exactly k successes in n independent trials each with success probability p.

Calculate the minimum number of bits needed to represent N distinct values (bits = ⌈log₂N⌉) from how many values you have.

Calculate the board feet of lumber from its thickness, width, and length using the formula (T x W x L) / 12.

Calculate the boiling point elevation (ΔTb = i · Kb · m) of a solution from the van 't Hoff factor, the ebullioscopic constant, and the molality.

Calculate the space diagonal, volume, and surface area of a rectangular box (cuboid) from its length, width, and height — diagonal = √(l²+w²+h²).

Calculate the final pressure of an ideal gas at constant temperature using Boyle's law (P₁V₁ = P₂V₂) from the initial pressure, initial volume, and final volume.

Work out how much salt to dissolve in water for a wet brine at your chosen salinity (salt = water × salinity / 100), in grams.

Calculate the buoyant force (F = ρgV) in newtons on a submerged or floating object from the fluid density and the displaced volume.

Calculate the capacitance (C = Q / V) in farads and microfarads of a capacitor from the charge it stores and the voltage across it.

Calculate the capacitive reactance (Xc = 1 / (2πfC)) in ohms of a capacitor at a given AC frequency from its capacitance and frequency.

Calculate the maximum (Carnot) efficiency of a heat engine, η = 1 − T_cold / T_hot, from the cold and hot reservoir temperatures in kelvin.

Calculate the center of mass (balance point) of two point masses on a line from their masses and positions: x_cm = (m1·x1 + m2·x2) / (m1 + m2).

Calculate the centripetal acceleration (a = v²/r) in metres per second squared for an object moving in a circle, from its speed and the radius.

Calculate the final volume of a gas at constant pressure using Charles's law (V₁/T₁ = V₂/T₂) from its initial volume and absolute Kelvin temperatures.