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.
Tree age calculator
A northern red oak 24 inches across at breast height with a growth factor of 4 is about 96 years old: the calculator multiplies trunk diameter by the species…
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Tree height calculator
Standing 50 m from the trunk and sighting the crown at 30 degrees puts it 28.867 m above your eye: the calculator multiplies distance by the tangent of the…
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Tree leaves calculator
A crown of 12 cubic metres with 250 leaves per cubic metre holds about 3000 leaves: the calculator multiplies crown volume by leaf density and an optional fill…
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Trihybrid Punnett square
Crossing AaBbCc with AaBbCc gives 64 equally likely offspring, 27 genotypes and the classic 27:9:9:9:3:3:3:1 phenotype ratio: the calculator builds the full 8…
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Turtle tank size calculator
A turtle with a 4-inch shell needs at least 40 US gallons of water: the calculator applies the keepers' rule of ten gallons per inch of straight shell length…
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Water potential calculator
A 0.1 mol/L sucrose solution at 295 K in an open beaker has a water potential of about −2.45 bars: the calculator adds solute potential and pressure potential…
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Water-soluble fertilizer calculator
Turns a ppm target into grams on the scale: 200 ppm nitrogen in 10 litres with a 20% bag needs 10 grams of product.
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Benzo[a]pyrene exposure
Breathing air with 1 ng/m³ of benzo[a]pyrene for 10 years means 20 ng inhaled each day and 73,000 ng in total for a 70 kg adult: a transparent screening dose…
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Car vs bike CO2
A 10 km trip in a car using 8 L/100 km burns 0.8 litres of petrol and emits about 1.85 kg of CO2, against 0.21 kg by bicycle, so riding saves 1.638 kg.
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Cigarette butts calculator
Twenty cigarettes a day leave 7,300 butts a year, about 1.46 kg of cellulose-acetate filters that do not dissolve: see a year of smoking as one pile for a quit…
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CO2 breathing emission calculator
Ten people working eight hours at 0.045 kg per person-hour breathe out 3.6 kg of CO2 over 80 person-hours, a quick and auditable figure for a classroom, office…
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Cryptocurrency footprint calculator
One Bitcoin transaction is about 700 kWh and 336 kg of CO2e, while ten thousand Ethereum transfers add up to 300 kWh and 120 kg: compare coins with a…
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Drip faucet calculator
Sixty drips a minute at 0.25 mL each for thirty days waste 648 liters, from a leak that never looks dramatic: count the drops for one minute and see the total.
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Fish mercury calculator
Two weekly 113 g servings of salmon at 0.022 ppm give 4.972 µg of mercury, while one serving of canned albacore gives 39.55 µg: compare plates on one scale…
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Flight CO2 emissions calculator
A 1,000 km hop at 0.15 kg per passenger-kilometre puts 150 kg of CO2 on one traveller's account and 600 kg on a family of four: a transparent first number for a…
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Hand dryers vs paper towels
Eight hand dries a day add up to 2,920 a year: 13.432 kg of CO2e with a high-speed dryer against 43.8 kg with paper towels, a saving of 30.368 kg.
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Hydroelectric power calculator
Two cubic metres of water per second falling through a 10 m net head at 85 percent efficiency deliver 166.77 kW: a screening figure for a micro-hydro site or a…
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Lotka-Volterra equations
Start with 10 prey and 5 predators, set the four rates and get the population at every step: with rates of 1.1, 0.4, 0.1 and 0.4 the coexistence equilibrium…
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Olympic Games carbon footprint
Half a million attendees travelling 4,000 km each, 80,000 MWh of venue energy and 200,000 m² of new floor add up to 432,000 tonnes of CO2e, with travel alone at…
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PHEV economy calculator
A 100-mile trip with 40 miles of electric range, 28 kWh per 100 miles and 50 mpg on gas uses 11.2 kWh and 1.2 gallons, folded into one MPGe figure.
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Plastic footprint calculator
Seven bottles, ten bags and twenty packaging items a week add up to 27.82 kg of single-use plastic a year.
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Shannon diversity index calculator
Counts of ten, twenty, thirty and forty individuals across four species give a Shannon index of 1.279854.
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Solar panel calculator
Ten 400 W panels with 5 peak sun hours and 80% system efficiency make 16 kWh a day and 5840 kWh a year.
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Solar panel wattage calculator
Ten 400 W panels at 5 peak sun hours form a 4 kW array that yields 20 kWh a day and 7300 kWh a year before any losses.
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Vegan footprint calculator
Eating vegan every day of the week avoids 910 kg of CO2e, 546,000 liters of water and 3640 m² of farmland in a year compared with a typical mixed diet.
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Water demand calculator
Ten thousand people using 150 liters each demand 1,500,000 liters a day and 547,500,000 liters a year.
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Wind turbine profit calculator
An 80 m rotor at an average 7 m/s produces over three million kWh a year; this calculator turns that energy into yearly profit at your electricity price, after…
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Zero-waste Christmas tree calculator
Renting the same 2 m Nordmann fir for 5 seasons instead of buying a new one each year avoids 12 kg of CO2.
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Bloodstain angle of impact calculator
A stain 5 mm wide and 10 mm long gives a ratio of 0.5 and an impact angle of 30°; the rounder the stain, the steeper the angle.
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Activation energy calculator
If a rate constant rises from 0.0001 to 0.0004 when the temperature goes from 300 K to 310 K, the activation energy is 107194.52158060214 J/mol.
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Alligation calculator
Reaching 50% from an 80% stock and a 30% stock takes 20 parts of the first and 30 of the second, a 2:3 ratio, or 40% and 60% of the blend.
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Atomic mass calculator
Turn isotope data into a table atomic mass: chlorine, with 0.7577 of its atoms at 34.96885 amu and 0.2423 at 36.9659 amu, comes to 35.452735215 amu.
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Avogadro calculator
Turn an amount in moles into a particle count with the exact Avogadro constant: 1 mol is 6.02214076 × 10²³ atoms, molecules, ions or formula units.
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Boiling point calculator
Get the actual boiling temperature of a solution, not just the rise: water with 1 mol/kg of solute and a Kb of 0.512 boils at 100.512 °C.
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Calibration curve calculator
Turn five standards from 0 to 4, with readings from 0.01 to 0.81, into a calibration line with a slope of 0.2, an intercept of 0.01 and an R² of 1.
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Chemical name from formula
Type a well-known formula and get the compound's everyday English name: H2O returns Water and C6H12O6 returns Glucose.
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Combustion reaction calculator
Type the carbon and hydrogen counts of a hydrocarbon and get its balanced complete-combustion equation: 3 carbons and 8 hydrogens give C3H8 + 5 O2 → 3 CO2 + 4…
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Crude protein calculator
Convert a lab nitrogen result into the crude protein figure used on labels and ration sheets: 16 % nitrogen times the default factor of 6.25 gives 100 %…
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Hydraulic detention time calculator
Work out how long liquid stays in a tank: 100 m³ fed at 10 m³ per hour gives a detention time of 10 hours, and 500 litres at 25 litres per minute gives 20…
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Effective nuclear charge calculator
Find the charge an electron really feels once inner electrons shield the nucleus: a sodium 3s electron with Z of 11 and S of 8.8 feels 2.2, not the full 11.
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Electrolysis calculator
Turn a current and a run time into grams of product: 0.8 A for 7200 seconds through a silver bath passes 5760 coulombs and plates a little over 6 g of silver.
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Entropy calculator
Work out an entropy change by either textbook route: 1000 J absorbed at 300 K raises the entropy by just over 3 J/K, or send standard molar entropies for both…
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Graham's law of diffusion calculator
Helium at 4 g/mol diffuses twice as fast as methane at 16 g/mol, because the rate falls with the square root of molar mass.
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Heat of combustion calculator
Burning 2 kg of a fuel with a calorific value of 42,000,000 J/kg releases 84,000,000 joules. Enter the fuel mass and its heating value in matching units to get…
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Langmuir isotherm calculator
See how much of a surface the gas molecules cover: with a Langmuir constant of 2 per atm and a partial pressure of 0.5 atm, the product KP is 1 and the coverage…
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Kp calculator
Get the pressure equilibrium constant straight from partial pressures: for 2SO2 + O2 ⇌ 2SO3 with 0.4 atm of SO3, 0.2 atm of SO2 and 0.1 atm of O2, Kp comes out…
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Liquid ethylene density calculator
Find how dense liquid ethylene is wherever you measure it: at its normal boiling point of 169.4 K the saturated liquid weighs 568.874115703 kg/m³, and any value…
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Miller indices calculator
Intercepts of 2, 3 and 4 on the a, b and c axes name the plane (6 4 3). Enter the three intercepts in lattice-constant units, use zero for an axis the plane…
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Mixing ratio calculator
A vapor pressure of 12.27 hPa at a total pressure of 1013.25 hPa gives 7.624468021339 g of water vapor per kilogram of dry air.
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Molar ratio calculator
36 g of water and 32 g of oxygen look alike on a balance, yet they stand in a 2:1 mole ratio. Enter both masses and molar masses to get the two mole amounts…
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Neutralization calculator
25 mL of 0.1 M hydrochloric acid needs 25 mL of 0.1 M sodium hydroxide to reach the equivalence point.
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Percent ionic character calculator
An electronegativity difference of 1.9, as in hydrogen fluoride, gives about 59.4 % ionic character: enter the gap between the two atoms and get the ionic and…
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Net ionic equation calculator
Silver, nitrate, sodium and chloride ions on one side and solid silver chloride with sodium and nitrate on the other reduce to Ag+(aq) + Cl-(aq) → AgCl(s).
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pKa calculator
A Ka of 1 × 10⁻⁷ is exactly pKa 7, and acetic acid's 1.8 × 10⁻⁵ is about 4.74: enter a positive Ka, typed plainly or in scientific notation, and get its pKa for…
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Raoult's law calculator
A component at mole fraction 0.4 with a pure vapor pressure of 92 contributes a partial pressure of 36.8 in the same unit, whether torr, kPa or atm.
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Q10 calculator
With a Q10 of 2, warming a reaction by 10 degrees doubles its rate, a 100 % increase. Enter Q10 and the temperature change, whether warming or cooling, to get…
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Resuspension calculator
10 mg of freeze-dried reagent aimed at 2 mg/mL needs 5 mL of diluent. Enter the dry mass, or a cell count, and the working concentration in matching units to…
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Standard temperature and pressure calculator
One mole of gas at 1 atm and 0 °C fills 22.414 L, a little more than the rounded 22.4. Pick volume, moles or pressure as the unknown, give the other two, and…
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Titration calculator
If 25 mL of 0.1 M titrant reaches the end point against a 50 mL sample in a one-to-one reaction, the sample is 0.05 M.
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Vapor pressure calculator
With water's Antoine constants, 100 °C gives about 760 mmHg, the normal boiling point, and 25 °C about 23.8 mmHg.
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