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.
Weak acid pH calculator
A weak acid at 0.1 mol/L with a Ka of 0.000018 has a pH just under 3: enter the concentration and Ka or pKa and get the exact pH next to the square-root…
Free · Runs in your browser
Weak base pH calculator
Solving the weak-base equilibrium for 0.1 mol/L and a Kb of 0.000018 puts the pH a little above 11: enter the concentration and Kb and get the hydroxide…
Free · Runs in your browser
pKb from Kb calculator
Ammonia's Kb of about 1.8 × 10⁻⁵ becomes a pKb of about 4.74: enter any positive Kb from a table, a lab fit or another calculator and get its pKb directly…
Free · Runs in your browser
pOH calculator
0.001 mol/L of hydroxide is pOH 3 and pH 11, a clearly basic solution: enter [OH−] in moles per litre and get pOH, pH, the matching [H+] and an acidic, neutral…
Free · Runs in your browser
pOH calculator
0.1 mol/L of hydroxide ions is pOH 1, while the pure-water level of 1 × 10⁻⁷ mol/L is the neutral pOH 7: type a known [OH−] and get the pOH, an alkalinity label…
Free · Runs in your browser
PPB to molarity calculator
1000 ppb of a solute with a molar mass of 58.44 g/mol, in a solution of density 1 g/mL, is 0.000017111567 mol/L.
Free · Runs in your browser
PPM calculator
0.002 g of solute in 1000 g of solution is 2 ppm, or 2000 ppb. Enter the solute mass in grams and then either the solution mass or, for a dilute water sample…
Free · Runs in your browser
PPM to mg/L calculator
10 ppm in water of density 1 g/mL is 10 mg/L, and a denser liquid gives proportionally more milligrams per litre.
Free · Runs in your browser
PPM to molarity calculator
100 ppm of sodium chloride (58.44 g/mol) is 0.001711156742 mol/L under the dilute-water rule that 1 ppm equals 1 mg per litre.
Free · Runs in your browser
PPM to PPB converter
1.5 ppm of residual chlorine is 1500 ppb and 1500000 ppt, because each step from million to billion to trillion is a factor of 1000.
Free · Runs in your browser
Pseudo-first-order rate constant calculator
A second-order constant of 0.05 M⁻¹ s⁻¹ with a 0.5 M excess gives an observed constant k′ of 0.025 s⁻¹, simply k times the excess concentration.
Free · Runs in your browser
Radioactive decay calculator
100 atoms with a decay constant of 0.1 and 5 units of time on the same time base leave 60.6530659713 atoms, so 0.393469340287 of the sample has decayed.
Free · Runs in your browser
Raoult's law vapor pressure calculator
Water at 23.8 torr with a solvent mole fraction of 0.85 gives a solution vapor pressure of 20.23 torr, a drop of 3.57 torr caused by the dissolved solute.
Free · Runs in your browser
Raoult's law two-component calculator
A liquid with 0.4 of component 1 (pure vapor pressure 92) and 0.6 of component 2 (35) has partial pressures of 36.8 and 21, a total of 57.8 in the same unit.
Free · Runs in your browser
Rate constant at new temperature calculator
A rate constant of 0.0001 at 300 K with an activation energy of 50000 J/mol becomes 0.000190908785 at 310 K, almost double after a 10-degree rise.
Free · Runs in your browser
Rate from stoichiometry calculator
A product forming at 0.24 mol per litre per second with a coefficient of 2 gives a reaction rate of 0.12, the single rate every species in the balanced equation…
Free · Runs in your browser
Rate law calculator
With k at 0.5, A at 0.1 (first order) and B at 0.2 (second order), the reaction runs at a rate of 0.002, with an overall order of 3.
Free · Runs in your browser
Reactant mass needed calculator
To make 13.75 g of a product with a molar mass of 44 g/mol from a reactant of 32 g/mol in a 1:1 ratio, weigh out 10 g of reactant.
Free · Runs in your browser
Reaction quotient Q calculator
With reactants at 0.5 and 0.3 (coefficients 1 and 3) and a product at 0.2 (coefficient 2), Q is 0.04 divided by 0.0135, or 2.962962962963.
Free · Runs in your browser
Reaction rate calculator
A concentration change of 0.5 mol/L over 10 s is an average rate of 0.05 mol/L per second. Enter the change in concentration and the elapsed time to get the…
Free · Runs in your browser
Reduced properties calculator
A gas at 50 bar and 400 K, with a critical pressure of 100 bar and a critical temperature of 300 K, has a reduced pressure of 0.5 and a reduced temperature of…
Free · Runs in your browser
Relative vapor pressure lowering calculator
Pure water at 23.8 torr and a solution at 20.23 torr give a lowering of 3.57 torr, a relative lowering of 0.15 or 15 %.
Free · Runs in your browser
Reverse osmosis net driving pressure
With a feed osmotic pressure of 25 bar and a pump at 55 bar, the net driving pressure is 30 bar, so reverse osmosis can proceed.
Free · Runs in your browser
Root-mean-square speed calculator
Oxygen at 32 g/mol and 298.15 K has a root-mean-square speed of 482.081135827716 m/s. Enter the molar mass in g/mol or kg/mol and the temperature in kelvin to…
Free · Runs in your browser
Second-order concentration calculator
Starting at 0.5 mol/L with a second-order rate constant of 0.1 L/(mol·s), 0.333333333333 mol/L remain after 10 s, or 0.666666666667 of the start.
Free · Runs in your browser
Second-order half-life calculator
A second-order rate constant of 0.5 L/(mol·s) with an initial concentration of 0.1 mol/L gives a half-life of 20 seconds, because the half-life is one over k…
Free · Runs in your browser
Serial dilution calculator
A 1 M stock diluted ten-fold over five steps ends at 0.00001 M. Enter the stock, the factor and the steps, and see each tube's concentration beside its…
Free · Runs in your browser
First-order shelf-life calculator
With a first-order rate constant of 0.001 per day, ten percent of the active substance is gone after about 105.36 days.
Free · Runs in your browser
Solution density from mass percent
A 20 % solution of a solute at 1.84 g/mL in a solvent at 1 g/mL comes out at about 1.1 g/mL. Enter the mass percent and both pure densities to estimate the…
Free · Runs in your browser
Solution freezing point calculator
Water with Kf of 1.86 and a 1 mol/kg non-electrolyte freezes at −1.86 °C instead of 0 °C. Enter the solvent's freezing point, molality, Kf and particle factor…
Free · Runs in your browser
Standard cell potential calculator
Copper at +0.34 V as cathode and zinc at −0.76 V as anode give a standard cell potential of +1.10 V.
Free · Runs in your browser
Stoichiometric air-fuel ratio calculator
Methane, with one carbon and four hydrogen atoms, needs about 17 kg of dry air per kg of fuel to burn completely.
Free · Runs in your browser
Mole ratio calculator
Six moles of hydrogen make four moles of ammonia, because N2 + 3 H2 → 2 NH3 sets a ratio of two to three.
Free · Runs in your browser
Theoretical yield calculator
With 2.5 moles of limiting reagent and two moles of product per mole consumed, the theoretical yield is 5 moles.
Free · Runs in your browser
Titration equivalence point volume calculator
Titrating 25 mL of a 0.1 M sample with 0.1 M titrant reaches equivalence at 25 mL. Enter the analyte concentration and volume and the titrant concentration…
Free · Runs in your browser
Titration pH at equivalence calculator
A 0.05 M salt of a weak acid with a Kb of 5.6 × 10⁻¹¹ gives a pH slightly above 8 at the equivalence point.
Free · Runs in your browser
Van der Waals molar volume calculator
At 10 bar and 298.15 K, a gas with a of 3.592 and b of 0.04267 needs slightly less room per mole than an ideal gas.
Free · Runs in your browser
Van't Hoff factor calculator
Sodium chloride with a degree of dissociation of 0.8 gives a van 't Hoff factor of 1.8, not 2. Enter the ions per formula unit and the degree of dissociation to…
Free · Runs in your browser
Vapor phase composition calculator
An ideal liquid that is 0.6 component 1 and 0.4 component 2, with pure vapor pressures of 100 and 50, makes a vapor that is 0.75 component 1.
Free · Runs in your browser
Vapor pressure lowering calculator
A solute mole fraction of 0.1 in a solvent with a vapor pressure of 23.8 lowers it by 2.38, leaving 21.42.
Free · Runs in your browser
Volume for target molarity calculator
0.5 mol of solute at a target of 0.25 mol/L needs 2 L of solution, which is 2000 mL. Enter the moles you have and the molarity you want to get the final volume…
Free · Runs in your browser
Volume percent to molarity calculator
10 % v/v ethanol becomes a molarity with two facts about the pure liquid: its density (0.789 g/mL) and its molar mass (46.07 g/mol).
Free · Runs in your browser
Gas volume to moles calculator
22.4 litres of gas at STP is roughly one mole, and 44.8 litres roughly two. Enter the volume in litres and the tool divides it by the molar volume at 0 °C and 1…
Free · Runs in your browser
Weight/volume percent calculator
5 g of solute in 100 mL of solution is 5 % w/v, or 0.05 g per mL. Enter the grams and the final volume in millilitres to get the concentration for a pharmacy…
Free · Runs in your browser
Weight-volume % to molarity calculator
A 5.85 % w/v sodium chloride solution, with a molar mass of 58.44 g/mol, is about 1 mol/L. Enter the label percentage and the molar mass and get the molarity…
Free · Runs in your browser
Precipitation ion product calculator
With a Ksp of 1.8 × 10⁻¹⁰ and both ions at 0.0001 mol/L in a one-to-one salt, Q is 10⁻⁸, so a precipitate forms.
Free · Runs in your browser
Brewster angle calculator
Finds the polarizing angle for any pair of media: light going from air (index 1) into glass (index 1.5) reflects fully polarized at about 56.3°.
Free · Runs in your browser
Critical angle calculator
Tells you where total internal reflection begins: light going from glass (index 1.5) towards air (index 1) is fully reflected beyond 41.8103148958°, the arcsine…
Free · Runs in your browser
Diffraction grating calculator
Find the angle where a grating sends each bright order, or learn that the order cannot exist: with lines 0.000001667 m apart and light of 5.5 × 10⁻⁷ m, order 3…
Free · Runs in your browser
F-stop calculator
Turn focal length and aperture diameter into the f-number printed on a lens: a 50 mm lens with a 25 mm entrance pupil is f/2, with a relative aperture of 0.5.
Free · Runs in your browser
Lens magnification calculator
Find out how big the image is and which way up: an object at 30 with its image at 60 gives a magnification of -2, an inverted image twice the object's size.
Free · Runs in your browser
Lens power calculator
Switch between focal length and diopters in one step: a focal length of 0.5 m is a power of 2 diopters, a converging lens, and the same reciprocal works in…
Free · Runs in your browser
Mirror equation calculator
Give the focal length and the object distance, and you get the image distance and magnification: an object at 30 in front of a mirror with focal length 10 forms…
Free · Runs in your browser
Single-slit diffraction calculator
Green light at 500 nm through a 0.1 mm slit puts its first dark fringe at 0.286480091241°. Enter the slit width, wavelength and order to locate any minimum and…
Free · Runs in your browser
Snell's law calculator
A ray going from air into glass at 30° bends to 19.4712206345°. Enter both refractive indices and the incidence angle measured from the normal to get the…
Free · Runs in your browser
Telescope magnification calculator
A 1000 mm objective with a 25 mm eyepiece gives 40x. Enter both focal lengths in the same unit to see how much larger a distant object appears, and how each…
Free · Runs in your browser
Beat frequency calculator
Two tones at 440 and 442 Hz beat twice per second: the beat rate is simply the gap between them. Enter both frequencies to get the beat, their average and which…
Free · Runs in your browser
Doppler effect calculator
A 440 Hz source approaching at 20 m/s through air at 343 m/s is heard about 6% higher. Add the wave speed and how the source and the observer move to get the…
Free · Runs in your browser
Doppler shift sound calculator
A 440 Hz siren rushing toward a listener at 20 m/s sounds roughly 6% higher, because its crests arrive packed closer together.
Free · Runs in your browser
Period to frequency calculator
A period of 0.02 seconds is a frequency of 50 Hz, and the reverse works the same way. Enter either the period or the frequency of any repeating signal and get…
Free · Runs in your browser