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.
Geostationary orbit calculator
Around Earth, a geostationary satellite orbits 35786.1067691 km above the equator, at a radius of 42164.2437691 km.
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Gravitational force calculator
Earth pulls on a 70 kg person at its surface with 687.421160537 newtons. Enter two masses in kilograms and the distance between their centres in metres to get…
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Hubble law calculator
A galaxy receding at 7,000 km/s with a Hubble constant of 70 km/s/Mpc lies 100 megaparsecs away, or 326156377.7 light-years.
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Light-year converter
Turn light-years into kilometres, parsecs and astronomical units in one step: one light-year is 9,460,730,472,580.8 km, about three tenths of a parsec.
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Orbital energy calculator
See how tightly a satellite is held by its planet: a 1000 kg satellite 6,778,000 m from Earth's centre has a total orbital energy of -29,403,156,980 joules.
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Orbital period calculator
Find how long one lap takes around a heavy central body: 149,597,870,700 m from a body of the Sun's mass gives about 365.25 days.
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Orbital velocity calculator
Find the speed that keeps a satellite on a circular orbit: 6,778,000 m from the centre of a body with Earth's mass, it must travel at 7,668.527496 m/s.
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Stellar parallax calculator
A parallax of 0.1 arcseconds puts a star 10 parsecs away, or 32.61563777 light-years. Enter the angle from a catalogue, a textbook or your own measurement and…
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Redshift calculator
A line emitted at 600 and observed at 660 has a redshift z of 0.1, a recession speed of 29979.2458 km/s.
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Roche limit calculator
With densities of 5514 and 3340 kg/m³ and a primary radius of 6371000 m, the rigid Roche limit is 9486901.0016 m and the fluid one 18372610.2884 m.
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Synodic period calculator
Work out the wait between matching line-ups of two planets: Earth at 365.25 days and Mars at 686.98 days meet again every 779.906893979 days, the rhythm of Mars…
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Rocket equation calculator
Turn exhaust speed and mass ratio into the velocity change a stage can deliver in empty space with no outside forces: 3000 m/s with a mass ratio of…
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Weight on other planets calculator
Find your weight on another world from your bathroom-scale reading: 70 kg on Earth becomes 26.39 on Mars, where gravity is 0.377 of Earth's, in the same unit…
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Actual yield calculator
A reaction with a theoretical yield of 10 g and a percent yield of 85 should give 8.5 g of product.
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Activation energy calculator
Rate constants of 0.0001 at 300 K and 0.0004 at 310 K give reciprocal temperatures of 0.003333333333 and 0.003225806452 and an activation energy of…
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Arrhenius pre-exponential factor calculator
A rate constant of 0.001 with an activation energy of 50000 J/mol at 298.15 K gives a pre-exponential factor of 574938.003485542, in the same units as k.
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Atom economy calculator
Measure how much of the reactants ends up in the product: hydrating ethene to ethanol, 46.07 g/mol on both sides, scores 100 %.
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Atoms to moles of compound calculator
Turn an atom count into moles of compound: 1.806642228 × 10²⁴ atoms grouped three per formula unit, as in water, make exactly 1 mol.
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Average atomic mass calculator
Get the weighted average behind a periodic-table value: boron's isotopes at 10.012937 u and 11.009305 u, with abundances 0.199 and 0.801, give 10.811027768 u.
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Average kinetic energy of gas calculator
Find how much motion energy a gas molecule carries on average: at 300 K it is 6.2129205 × 10⁻²¹ J, three-halves of Boltzmann's constant times the kelvin…
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Avogadro's law calculator
Predict a gas's new volume when only the amount of gas changes: 2 litres holding 1 mol become 6 litres at 3 mol, with temperature and pressure unchanged.
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Moles to atoms calculator
Convert both ways with Avogadro's number: 1 mol is 6.02214076 × 10²³ atoms, molecules or ions, and a particle count divided by that number gives moles.
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Bomb calorimeter calculator
Turn a bomb calorimeter reading into a molar heat of combustion: a calorimeter constant of 1255 J/K and a rise of 2.45 K for 0.01 mol of sample give −307475…
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Bond energy reaction enthalpy calculator
Estimate the heat of a reaction from average bond energies: breaking four C-H and two O=O bonds and forming two C=O and four O-H bonds gives −808 kJ/mol, an…
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Boyle's law calculator
Find the new pressure of a gas squeezed or expanded at constant temperature: 2 atm in 3 litres becomes 4 atm when the volume drops to 1.5 litres.
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Boyle's law final volume calculator
Find the volume a gas fills after an isothermal pressure change: 3 litres at 2 atm shrink to 1 litre at 6 atm, because pressure times volume stays the same.
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Buffer capacity calculator
Measure how strongly a buffer resists pH change: 0.1 mol/L of weak acid and 0.1 mol/L of its conjugate base give a capacity of 0.11512925465 mol/(L·pH), the…
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Buffer pOH calculator
Get the pOH of a weak-base buffer from pKb and two concentrations: with pKb 4.75 and 0.1 mol/L each of base and conjugate acid, the pOH is 4.75 and the pH at 25…
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C1V1 = C2V2 calculator
Solve a dilution for whichever value is missing: 50 mL of a 2 mol/L stock diluted to 0.5 mol/L makes 200 mL, a fourfold dilution.
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Calorimeter constant calculator
Calibrate your calorimeter: 1250 J of known heat that warms it by 2.5 °C gives a constant of 500 J/°C, ready to turn later temperature changes into energy.
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Calorimetry heat released calculator
Work out the heat a sample takes in or gives off: 1 kg of water with a specific heat of 4184 J/(kg·K), warmed by 1 K, absorbs 4184 J.
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Catalyst rate enhancement calculator
See how much a catalyst speeds up a reaction: cutting the activation energy from 75000 to 50000 J/mol at 298.15 K makes it roughly 24 thousand times faster.
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Cell potential from Gibbs free energy
Turn a standard Gibbs energy change into a cell voltage: −212300 J/mol with 2 electrons transferred gives 1.100167224278 V, the Daniell zinc-copper cell.
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Charles law final temperature calculator
Work out how hot a gas must be to reach a new volume at constant pressure: going from 2 to 4 litres at 273.15 K gives 546.3 K.
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Clausius–Clapeyron calculator
Find the temperature where a liquid reaches a target vapor pressure: from water at 101325 Pa and 373.15 K, with 40650 J/mol, you get the temperature for 2339…
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Colligative particle concentration calculator
Turn a formal molarity into the number of dissolved particles that actually counts: 0.1 mol/L of a salt with a van't Hoff factor of 2 gives 0.2 mol/L of…
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Collision theory rate calculator
Build a rate constant from how often molecules collide, how often they line up and how many clear the energy barrier: with Z of 10¹¹, a steric factor of 0.5 and…
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Combined equilibrium constant calculator
Get the overall equilibrium constant of a reaction built from steps: a step with K of 2.5 plus a reversed step with K of 0.4 gives 6.25, because constants…
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Combined gas law final pressure calculator
Work out the new pressure of a gas whose volume and temperature change together: 1 atm, 2 litres and 300 K squeezed to 1 litre at 600 K gives 4 atm.
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Combustion analysis calculator
Turn the products of a combustion train into an empirical formula: 3.52 g of CO2 and 1.44 g of H2O point to CH2.
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Common ion effect solubility calculator
Find how far a common ion pushes down a salt's solubility: with a Ksp of 1.8 × 10⁻¹⁰ and 0.1 mol/L of a shared ion, the molar solubility drops to 1.8 × 10⁻⁹…
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Gas compressibility factor calculator
Measure how far a real gas strays from ideal behaviour: at 101325 Pa, 273.15 K and 0.022414 m³/mol, Z comes out practically equal to 1.
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Concentration after evaporation calculator
See how strong a solution gets when solvent boils or dries off: evaporating 40 mL from 100 mL of a 2 M solution leaves 60 mL at 3.33 M, a factor of 1.67.
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Conjugate base to acid ratio calculator
Know the base-to-acid mix a buffer needs at a given pH: at pH 4.76 with a pKa of 4.76 the ratio is exactly 1, so both forms are equal.
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Faraday corrosion rate calculator
Convert a corrosion current into thickness lost per year: 1 µA/cm² on iron, at 55.845 g/mol, 7.87 g/cm³ and two electrons, eats away a little over 0.01 mm a…
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Van der Waals critical constants calculator
Turn the two van der Waals constants of a gas into its critical point: a nitrogen-like gas with a of 1.382 and b of 0.0387 L/mol has a critical volume of 0.1161…
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Partial pressures from mole amounts
Share out a mixture's total pressure from how many moles of each gas it holds: 2, 1 and 1 mol at a total of 1 atm give partial pressures of 0.5, 0.25 and 0.25…
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Gas mole fraction from partial pressure
Find what share of a gas mixture one component makes up: oxygen at 0.21 atm in air at 1 atm has a mole fraction of 0.21, or 21 %.
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Degree of dissociation calculator
See how much of a reactant has split apart by equilibrium: starting at 0.1 mol/L and ending with 0.02 mol/L undissociated gives a degree of dissociation of 0.8…
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Density calculator
Give any two of mass, volume and density and the calculator works out the third: 10 kg in 2 m³ is a density of 5 kg/m³.
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Dilution calculator
Fill in three of the four dilution values and get the missing one: 10 mL of a 2 M stock diluted to 0.5 M makes 40 mL of solution.
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Dilution factor calculator
Turn two volumes into a dilution factor and the share of stock left in the mix: 1 mL of solute in a 10 mL total is a tenfold dilution with a solute fraction of…
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pH after dilution calculator
See the new pH of a strong acid once you add water: pH 1 taken from 10 mL to 100 mL becomes pH 2. You also get the dilution factor, every step and whether the…
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Dilution to target ppm calculator
To make 100 mL at 50 ppm from a 1000 ppm stock, measure 5 mL of stock and add 95 mL of diluent. Enter the two concentrations and the final volume to get both…
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Dilution water to add calculator
Know exactly how much water to pour in: 100 mL of a 2 M stock needs 300 mL of water to reach 0.5 M, for 400 mL in total.
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Ebullioscopic constant calculator
Get a solvent's ebullioscopic constant from your own boiling-point data: a rise of 0.512 °C in a 1 mol/kg solution with a van 't Hoff factor of 1 gives Kb…
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Electrode potential vs pH calculator
Find the reversible potential of a hydrogen electrode from the solution's pH and the hydrogen pressure; at pH 7 and 1 bar it sits at −0.414 V.
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Electrolysis time calculator
Plan how long the current has to flow, since depositing 1 g of copper at 1.5 A takes just over half an hour.
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Electron configuration calculator
Type an atomic number and get the ground-state electron configuration: iron, Z 26, is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶, or [Ar] 4s² 3d⁶, with 8 valence electrons.
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Electrorefining efficiency calculator
Compare the metal you actually recovered with what the charge should have deposited: 9.2 g against a theoretical 10 g is 92 % current efficiency, with 0.8 g…
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