Science & Engineering

Calculate voltage, current, resistance and power using Ohm's law — enter any two values.

Calculate gravitational potential energy from mass and height using PE = m·g·h with g = 9.80665 m/s². Results in joules and kilojoules.

Convert between apparent magnitude, absolute magnitude, and distance for any star.

Calculate acceleration from the change in velocity over time using a = (vf − vi) / t. Get results in m/s² and in multiples of g.

Calculate the angular size of an object from its real size and distance, or solve for either one.

Angular velocity in rad/s and RPM from period, frequency or linear speed.

Calculate activation energy or rate constant using the Arrhenius equation and its two-temperature form.

Find the number of protons, neutrons and electrons in any atom or ion, plus nuclear binding energy from the Bethe-Weizsäcker formula.

Compute hydrogen-like atom energy levels, orbital radii and transition photon energy with the Bohr model.

Estimate reaction enthalpy from bond enthalpies: bonds broken minus bonds formed.

Calculate heat energy absorbed or released using q = mcΔT from mass, specific heat and temperature change.

Find the charge stored and energy held by a capacitor from its capacitance and applied voltage.

Find total capacitance of capacitors combined in series and in parallel from a list of capacitance values.

Find the maximum theoretical efficiency of a heat engine from hot and cold reservoir temperatures.

Centripetal (radial) acceleration from speed and radius, a=v²/r=ω²r.

Centripetal force for circular motion, F=mv²/r, with acceleration output.

Find the electrostatic force between two point charges using Coulomb's law from charge magnitudes and separation distance.

Find the critical angle for total internal reflection from two refractive indices.

Convert between decibel (dB) gain and power or amplitude ratios. Enter dB to find ratio, or ratio to find dB.

Compute the matter-wave wavelength of a particle from its mass and velocity using λ = h/(mv).

Convert sound intensity to decibels with L = 10·log10(I/I0), or find intensity from a dB level.

Calculate density from mass and volume using density = mass / volume. Get instant results in kg/m³ and g/cm³ for solids, liquids and gases.

Convert a solution's density and mass percent to molarity using the solute's molar mass.

Solve solution dilutions with M1V1 = M2V2. Find the missing concentration or volume instantly.

Convert distance modulus to distance (and back) in parsecs and light-years.

Compute the observed frequency shift for sound from moving sources and observers using the Doppler formula.

Calculate the drift velocity of charge carriers in a conductor from current, carrier density and cross-section area.

Apply Einstein's E = mc² to any mass in kg, g, lb or oz — get rest energy in joules, kWh and TNT equivalents with step-by-step working.

Calculate EIRP (dBm, dBW, and watts) from transmitter power, antenna gain, and cable loss, plus optional power density at a given range.

Final velocities after a 1D elastic collision conserving momentum and energy.

Calculate the electric field strength of a point charge at a given distance and see how the field falls off with distance.

Compute the electric potential (voltage) created by a point charge at a distance and the energy of a test charge there.

Determine the empirical formula of a compound from element mass percentages or masses.

Calculate standard reaction enthalpy ΔH using Hess's law and standard heats of formation.

Calculate standard reaction entropy ΔS from product and reactant standard molar entropies.

Compute the equilibrium constant Kc from equilibrium concentrations and stoichiometric coefficients.

Minimum speed to escape a planet or star, v=√(2GM/R), with presets.

Apply the fan affinity laws to predict new flow rate, pressure, and shaft power when fan speed changes — ideal for VFD-controlled HVAC fans.

Calculate the mass and moles of substance deposited during electrolysis using Faraday's laws.

Calculate the induced EMF in a coil from the number of turns and the rate of change of magnetic flux.

Calculate Feed Conversion Ratio (FCR) for livestock, aquaculture, and poultry — how many kg of feed produce 1 kg of live weight gain.

Find the half-life and remaining concentration for a first-order reaction from its rate constant.

Calculate force from mass and acceleration using Newton's second law, F = m × a. Get instant results in newtons, kilonewtons and kilogram-force.

Calculate free fall time, impact velocity and distance from drop height under gravity.

Static or kinetic friction force from coefficient and normal force, f=μN.

Calculate Growing Degree Units (GDU/GDD) from daily temperatures and a base temperature. Predict crop development stages.

Calculate Gibbs free energy change ΔG from enthalpy, entropy and temperature, and test spontaneity.

Convert a mass in grams to number of moles using the molar mass of the substance.

Find a star's habitable (Goldilocks) zone inner and outer distances from its luminosity.

Find a real heat engine's thermal efficiency from heat input and work output, or from heat in and out.

Find buffer pH from pKa and the conjugate base to acid ratio using the Henderson-Hasselbalch equation.

Spring force from spring constant and displacement using F=kx; solve any variable.

Estimate a galaxy's distance from its recessional velocity using Hubble's law.

Solve the ideal gas law PV = nRT for pressure, volume, moles or temperature.

Find impulse from force and time or momentum change, J=FΔt=mΔv.

Forces and acceleration of a mass on a ramp with optional friction.

Convert acid dissociation constant Ka to pKa (and back), plus the conjugate Kb and pKb values.

Find an orbit's period from its semi-major axis and the central mass using Kepler's third law.

Solve constant-acceleration motion for velocity, time, displacement or acceleration.

Calculate the kinetic energy of a moving object from its mass and velocity using KE = ½mv². Results in joules, kilojoules and kilocalories.

Convert between gas-phase equilibrium constants Kp and Kc using Kp = Kc(RT)^Δn.

Convert Kc to Kp using Kp = Kc × (RT)^Δn and calculate ΔG° from the equilibrium constant at a given temperature.

Find molar solubility from Ksp (or Ksp from solubility) for a salt of any stoichiometry AxBy.

Calculate apparent power (kVA), real power (kW), reactive power (kVAR) and power factor for AC electrical systems.

Compute the heat for melting or boiling using Q = mL with latent heat of fusion or vaporization.

Calculate the series resistor value needed for an LED circuit from supply voltage, LED forward voltage and desired current — with E24 nearest standard value.

Convert astronomical distances between light-years, parsecs, astronomical units, kilometers and meters.

Identify the limiting reactant and excess amount from reactant masses and equation coefficients.

Calculate the Log Mean Temperature Difference (LMTD) for counterflow and parallel-flow heat exchangers from hot and cold inlet/outlet temperatures.

Compute the full Lorentz force on a charge from electric and magnetic field vectors and its velocity vector.

Calculate magnetic flux through a surface from magnetic field strength, area and the angle to the normal.

Find the magnetic force on a current-carrying wire in a magnetic field from current, length, field and angle.

Calculate the magnetic force on a charged particle moving through a magnetic field using F = qvB sin(theta).

Calculate the mass percent of a solute in a solution from solute mass and total solution mass.

Convert mass to energy with Einstein's E = mc². Enter a mass to see the equivalent energy in joules, kWh and megatons.

Calculate 1 MOA size at any shooting distance and find the scope clicks needed to correct point-of-impact error.

Calculate molality (mol/kg) from moles of solute and mass of solvent in kilograms.

Find the molar mass (g/mol) of any compound from its chemical formula like H2O, C6H12O6 or Ca(OH)2.

Calculate molarity (mol/L) from moles or grams of solute and solution volume.

Convert between grams, moles, and number of molecules using molar mass and Avogadro's number.

Calculate the mole fraction of each component in a mixture from their moles or masses.

Find the molecular formula from the empirical formula and the compound's molar mass.

Convert moles to number of particles (atoms, molecules, ions) using Avogadro's number, and back.

Convert moles of a substance to mass in grams using its molar mass. Fast mole-to-gram conversion.

Moment of inertia for common shapes (sphere, disk, rod) from mass and size.

Compute linear momentum p=mv, or solve for mass or velocity from momentum.

Find non-standard cell potential E from E°, electrons transferred and the reaction quotient Q.

Calculate magnification from image and object distances or heights for lenses and mirrors.

Circular orbit speed and period from central mass and orbital radius.

Calculate the capacitance of a parallel plate capacitor from plate area, separation and dielectric constant.

Find the percent by mass of each element in a chemical compound from its formula.

Calculate percent ionization, [H+] and pH of a weak acid from its Ka and initial concentration.

Calculate reaction percent yield from actual yield and theoretical yield.

Convert between period, frequency and angular frequency. Enter period or frequency to get T, f and ω instantly.

Find pH, pOH, [H+] and [OH-] of a solution. Convert hydrogen ion concentration to pH and back instantly.

Find the maximum kinetic energy of emitted electrons, stopping voltage and threshold frequency for the photoelectric effect.

Compute the energy of a photon from its frequency or wavelength using E = hf = hc/λ, in joules and electronvolts.

Convert Ka to pKa, calculate buffer pH with Henderson-Hasselbalch, and find % ionization of a weak acid.

Calculate pOH from hydroxide concentration and convert between pOH, pH, [OH-] and [H+] at 25 C.

Calculate power as work divided by time using P = W / t. Get instant results in watts, kilowatts and mechanical horsepower.

Convert between parts per million (ppm), ppb, mg/L and mass percent for dilute solutions.

Calculate pressure from force and area using P = F / A. Get instant results in pascals, kilopascals, psi and bar.

Range, maximum height and flight time of a projectile from speed, angle and launch height.

Calculate the Q10 coefficient — how much a biological or chemical reaction rate changes per 10 °C temperature rise — from two rate–temperature pairs.

Calculate remaining quantity, elapsed time or half-life for radioactive decay using N = N0·(1/2)^(t/T).

Compute reaction rate from the rate law rate = k[A]^m[B]^n and find the overall reaction order.

Find the RC time constant and plot the charging curve of a resistor-capacitor circuit over time.

Compute cosmological redshift z and the recessional velocity of a galaxy from spectral lines.

Calculate the contracted length of a fast-moving object using Lorentz contraction L = L0/γ.

Compute relativistic time dilation and the Lorentz factor for an object moving at a fraction of light speed.

Compute total resistance for any number of resistors wired in series and in parallel from a comma-separated list.

Find the resonant frequency of an RLC circuit and view the inductive and capacitive reactance curves versus frequency.

Convert actual flow rate (ACFM) to standard cubic feet per minute (SCFM) using actual pressure and temperature. Also outputs SCMH.

Calculate the event-horizon (Schwarzschild) radius of a black hole from its mass.

Apply the second-order integrated rate law to find half-life and concentration over time.

Period and frequency of a simple pendulum from length and gravity, T=2π√(L/g).

Calculate a sled's acceleration, net force, and friction on a slope given mass, angle, and kinetic friction coefficient.

Apply Snell's law n1·sinθ1 = n2·sinθ2 to find the refraction angle, refractive index or critical angle.

Calculate soil bulk density, porosity, void ratio, and optional water content from dry mass, total volume, and particle density.

Compute the magnetic field inside a solenoid from its number of turns, length and current.

Find the final concentration when mixing two solutions of different concentration and volume.

Calculate the heat energy needed to change a substance's temperature using Q = mcΔT, with mass, specific heat and temperature change.

Elastic potential energy stored in a spring, PE=½kx², from stiffness and stretch.

Compute standard cell potential E°cell from cathode and anode reduction potentials and check spontaneity.

Estimate a star's main-sequence lifetime from its mass relative to the Sun.

Find a star's luminosity from its radius and surface temperature using the Stefan-Boltzmann law.

Convert mass of a reactant to mass of a product using mole ratio and molar masses.

Compute the surface gravity of a planet, moon, or star from its mass and radius.

Compute the synodic period between two orbiting bodies from their sidereal orbital periods.

Convert electrical conductivity (EC) to TDS in ppm and check water quality against EPA and WHO drinking water limits.

Work out telescope magnification, focal ratio and exit pupil from focal lengths and aperture.

Find a telescope's resolution, light-gathering power and limiting magnitude from its aperture.

Falling object terminal speed from mass, area, drag coefficient and air density.

Calculate the theoretical yield of a product from reactant amount, mole ratio and molar masses.

Calculate linear, area or volumetric thermal expansion from temperature change and expansion coefficient.

Use 1/f = 1/do + 1/di to find image distance, focal length or object distance for lenses and mirrors.

Calculate the differential tidal force and acceleration exerted on a body by a distant mass.

Rotational torque from force, lever arm and angle, τ=rF·sinθ.

Calculate transformer secondary voltage, current and turns ratio for an ideal transformer from primary values.

Newton's law of gravitation force between two masses, F=Gm₁m₂/r².

Calculate average velocity from distance and time using v = d / t. Get instant results in metres per second, kilometres per hour and miles per hour.

Calculate electrical power in watts from any two of voltage, current or resistance using P = V × I, P = V²/R or P = I²R.

Find wave speed, frequency or wavelength using v = f × λ. Enter any two values to solve for the third.

Calculate wavelength from wave speed and frequency using λ = v / f. Works for light, sound and radio waves, with results in metres, centimetres and nanometres.

Convert mass to weight W=mg on Earth, Moon, Mars and other bodies.

See how much you would weigh on the Moon, Mars, Jupiter and every other planet in the Solar System.

Find the peak emission wavelength of a blackbody from its temperature, and vice versa.

Calculate mechanical work from force, distance and the angle between them using W = F·d·cos(θ). Results in joules, kilojoules and kilocalories.

Net work as change in kinetic energy, W=½m(v²−u²), from mass and speeds.