Science
1,125 science calculators for chemistry, physics, biology, astronomy and the Earth sciences. Each one states the relation it uses and the units it expects, so class problems, lab work and quick checks come out right, free in your browser.
Speed distance time calculator
Enter any two of speed, distance and time and the third is worked out: a distance of 100 covered in a time of 2 means a speed of 50.
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Dew point calculator
Find the temperature at which moisture starts to condense: air at 25 °C and 60% humidity has a dew point of 16.69 °C.
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Moon phase calculator
Enter a date and see the Moon's phase: on 1 January 2026 the Moon is 12.421 days old, 93.9% lit and waxing gibbous.
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Kepler's third law calculator
Scale one known orbit to another: if Earth takes 1 year at 1 AU, a body at 4 AU from the Sun takes 8 years.
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Physical size from angular diameter
The Moon spans 31.5 arcminutes at 384400 km, which makes it 3522.248963449756 km across. Enter any angular diameter in radians, degrees, arcminutes or…
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Propellant mass fraction calculator
To gain 9400 of velocity with an exhaust velocity of 3500, 0.931827518029 of the rocket's starting mass must be propellant, a mass ratio of 14.668675264333.
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Limiting reactant calculator
Find the reactant that stops the reaction and the leftover of the other: 5 mol of hydrogen with coefficient 2 against 3 mol of oxygen with coefficient 1 makes…
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Moles of product calculator
2.5 moles of reactant with coefficients 2 and 1 give 1.25 moles of product, through a mole ratio of 0.5.
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Electrolysis overpotential calculator
Applying 2 V to a cell whose reversible decomposition voltage is 1.23 V means an overpotential of 0.77 V, the extra push your power supply delivers beyond…
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Percent yield calculator
Recovering 8.5 g of product when stoichiometry predicts 10 g is an 85 % yield: enter the actual and theoretical amounts in grams, moles or any shared unit and…
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Acoustic resonance Q factor calculator
Rates how sharp an acoustic resonance is: a 440 Hz peak with a 2.2 Hz half-power bandwidth has a Q of 200, so it rings for many cycles before fading.
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Lensmaker's equation
Check a textbook lens in seconds: crown glass near index 1.5 with symmetric radii of 0.1 m and -0.1 m focuses at 0.1 m, a converging lens of 10 diopters, under…
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Wavelength calculator
Divide the wave speed by the frequency and get the wavelength in metres: sound at 340 m/s with a 440 Hz pitch spans a little over three quarters of a metre per…
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Charles's law calculator
2 litres of gas at 300 K warmed to 600 K expands to 4 litres, because volume over kelvin temperature stays constant at fixed pressure.
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First-order reaction time calculator
Find the time a first-order reaction needs to fall from one concentration to another: with k of 0.1 per second, 1 mol/L drops to 0.5 mol/L in about 6.931…
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Absolute magnitude calculator
A star of apparent magnitude 0 at 100 parsecs has an absolute magnitude of -5, while one of magnitude 5 at 10 parsecs stays at 5.
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Light travel time calculator
Find how long light needs to cover a distance in space: one astronomical unit takes about 499 seconds, the familiar eight-minute delay of sunlight.
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Planet density calculator
Earth's mass of 5.972e+24 kg and radius of 6371000 m give a mean density of 5513.2587385891 kg/m³.
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Schwarzschild radius calculator
A mass of 1.9885e+30 kg, about the Sun's, has a Schwarzschild radius of 2953.3839390285 m, roughly 2.95 km.
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Surface gravity calculator
Get the pull at the surface of any world from its mass and size: 5.972 × 10²⁴ kg and 6371000 m, Earth's values, give 9.8199734262 m/s², ready for weight and…
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Telescope resolution calculator
See the diffraction limit of any telescope from its size and the colour of light: a 10 cm aperture at 550 nm resolves 1.3840368499 arcseconds, and larger…
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Arrhenius equation calculator
With an activation energy of 50000 J/mol at 298.15 K and a pre-exponential factor of 10¹², the rate constant is 1737.367006085, in the same units as the factor.
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Arrhenius temperature calculator
Run the Arrhenius equation backwards: enter k, A and Ea and get the temperature in kelvin, 298.15 K in the worked example with Ea of 50000 J/mol.
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Average molecular speed calculator
Find how fast gas molecules move on average: oxygen at 32 g/mol and 298 K averages about 444 m/s. Enter the molar mass in g/mol and the temperature in kelvin…
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Average rate of reaction calculator
Get the mean rate of a reaction from two readings: a concentration change of 0.12 over 30 time units gives 0.004 per unit of time.
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Avogadro's law moles calculator
Find the moles of gas that match a new volume at fixed temperature and pressure: 1 mol in 2 litres corresponds to 2 mol in 4 litres.
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Boiling point elevation calculator
See how far a dissolved solute pushes up the boiling point: 0.5 mol/kg with a water-like Kb of 0.512 adds 0.256 K, or 0.512 K when each formula unit splits into…
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Born-Haber lattice energy calculator
Close the Born-Haber cycle and get the lattice energy of an ionic solid: for sodium chloride, formation −411, sublimation 108, ionization 496, dissociation 121…
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Charles's law final volume calculator
See how much a gas expands or shrinks when its temperature changes at constant pressure: 2 litres at 300 K become 4 litres at 600 K.
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Vaporization enthalpy calculator
Get a liquid's latent heat of vaporization from two vapor-pressure readings: a pressure that doubles from 1000 to 2000 between 300 K and 310 K gives the…
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Combined gas law final volume calculator
See what volume a gas takes when pressure and temperature change together: 5 litres at 2 atm and 250 K become 20 litres at 1 atm and 500 K.
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Cryoscopic constant calculator
Recover a solvent's freezing-point constant from your own measurement: a depression of 0.93 K at 0.5 mol/kg with a van 't Hoff factor of 1 gives a Kf of 1.86…
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Decay constant calculator
Switch between the three ways of describing exponential decay: a half-life of 10 time units gives a decay constant of about 0.0693 per unit and a mean lifetime…
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Degree of dissociation calculator
Turn a measured van 't Hoff factor into the share of an electrolyte that actually ionizes: a factor of 1.8 for a salt that splits into two ions means a degree…
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Dilution factor calculator
Find how many times a stock gets diluted and how much diluent to add: 1 mL brought up to 10 mL is a tenfold dilution with 9 mL of diluent, a 1:9 mix.
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Degree of dissociation calculator
Turn an equilibrium constant and a starting concentration into the share that splits apart: Kc 0.05 with 0.1 mol/L gives α 0.5, so 50 % dissociates.
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Empirical formula from percent composition calculator
Turn mass percentages into the simplest whole-number formula: 11.19 % hydrogen and 88.81 % oxygen, with their atomic masses, give H2O.
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Heat of formation from reaction calculator
Solve for the missing heat of formation in a balanced equation: methane combustion at −890 kJ/mol, with −393.5 for carbon dioxide, −285.8 for water and 0 for…
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Molar enthalpy calculator
Turn a calorimeter's total heat into a molar enthalpy: −890 kJ measured for 1 mol reacted is −890 kJ/mol, and released heat keeps its negative, exothermic sign.
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Equilibrium constant from Gibbs calculator
Turn a standard Gibbs energy change into an equilibrium constant: −10,000 J/mol at 298.15 K gives K above one, so products are favored, while a ΔG° of zero…
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Equilibrium yield calculator
See how close a reversible reaction gets to full conversion: 75 mol of product at equilibrium out of a theoretical maximum of 100 mol is a 75% equilibrium…
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Formula units calculator
Turn grams of a salt into a count of formula units: 58.44 g of sodium chloride at 58.44 g/mol is exactly one mole, or 6.02214076 × 10²³ formula units.
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Fraction of molecules above Ea calculator
Estimate the share of molecules with enough energy to clear a reaction barrier: at 50,000 J/mol and 298.15 K only about 1.7 × 10⁻⁹ of them do, and that fraction…
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Freezing point depression calculator
Predict how far a solution's freezing point falls, in kelvin: 0.5 mol/kg of a non-electrolyte in water, with a Kf of 1.86, gives a drop of 0.93 K, and a strong…
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Fuel energy content calculator
Find the total energy a fuel can release: 2 kg of fuel with an energy density of 45 MJ/kg holds 90 MJ.
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Effusion remaining fraction calculator
See how a pinhole leak changes a gas mixture: with hydrogen at 2.016 g/mol and oxygen at 32 g/mol, at a time ratio of 0.5 roughly 14% of the hydrogen is left…
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Gas stoichiometry volume calculator
Predict how much gas a reaction gives off at your conditions: 1 mol of reactant with a 1:1 gas product at 1 atm and 273.15 K yields about 22.4 litres, and any…
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Gas volume at STP calculator
Turn moles of gas into litres at classic STP: 1 mol fills 22.4 L and 2.5 mol fill 56 L at 0 °C and 1 atm, the molar volume used in textbook gas stoichiometry.
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Gas temperature from P, V, n calculator
Recover the absolute temperature of an ideal gas: 1 mol at 1 atm in 22.414 L sits at about 273 K, the ice point.
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Gas volume at NTP calculator
One mole of ideal gas fills 24.0 litres at NTP, so the volume is simply the moles times 24.0. Enter the amount of gas and read the litres at 20 °C and 1 atm…
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Gibbs free energy calculator
For ΔH of −92.4 kJ/mol, ΔS of −0.1987 kJ/(mol·K) and 298.15 K, ΔG comes out at −33.157595 kJ/mol, which is spontaneous.
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Grams of product from moles calculator
Two moles of water at 18.015 g/mol make 36.03 grams of product. Enter the moles from your mole-ratio step and the product's molar mass to get the mass in grams…
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Grams of solute for molarity calculator
A 0.5 M sodium chloride solution in 0.25 litres needs 0.125 moles, which is 7.305 grams at 58.44 g/mol.
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Instantaneous rate from tangent calculator
Get the reaction rate at one moment from two close readings: 0.85 mol/L at 10 s and 0.8 mol/L at 12 s give 0.025 mol/L per second, the local tangent rather than…
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Equilibrium constant at new temperature
Find how an equilibrium constant shifts with temperature: a K of 0.05 at 298.15 K with a reaction enthalpy of −58000 J/mol falls to 0.0015616472 at 350 K, as an…
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Kp from partial pressures calculator
Work out Kp from one list of equilibrium pressures: for N2 + 3H2 ⇌ 2NH3 at 0.5, 1.5 and 0.1 atm, with reactants entered as negative coefficients, Kp is…
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Ksp from solubility calculator
Turn a molar solubility into a solubility product: a 1:1 salt such as silver chloride that dissolves to 0.01 mol/L has a Ksp of 0.0001, while calcium fluoride…
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Le Chatelier pressure shift calculator
See which way an equilibrium moves when you raise the pressure: ammonia synthesis has 4 moles of gas on the reactant side and 2 on the product side, so it…
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Limiting reagent from masses calculator
Tell which of two weighed reactants runs out first: 10 g of hydrogen at 2 g/mol with coefficient 2 against 10 g of oxygen at 32 g/mol with coefficient 1 makes…
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Mass percent to molality calculator
A 10% sodium chloride solution, with a molar mass of 58.44 g/mol, is about 1.901 mol/kg. Convert the weight percent printed on a bottle into the molality that…
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