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.
Depth of field far limit calculator
See how far behind your subject sharpness reaches: a 50 mm lens at f/8 focused at 5 m stays acceptably sharp to a point between 9 and 10 m away, and the result…
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Incidence angle from Snell's law calculator
Start from the refracted ray you need and get the incoming angle: from air at index 1 into glass at 1.5, a refraction angle of 19.4712206345° needs an incidence…
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Spherical mirror object distance calculator
Choose the image distance you need and see where the object must go: with a focal length of 10 and an image distance of 30, the object sits at 15, in the same…
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Cauchy Dispersion Refractive Index Calculator
Evaluates the Cauchy equation for one wavelength: with coefficients of 1.5046 and 0.0042 µm² at 0.55 µm, the refractive index is 1.518484297521.
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Double-slit bright fringe position calculator
Predict where a bright band lands on the screen: order 3 with 6e-7 m light, slits 0.00025 m apart and a screen 2 m away sits 14.4 mm from the centre, using the…
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Relative refractive index calculator
With air at 1 and glass at 1.5, the relative index of glass to air is 1.5, so glass is the optically denser medium.
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Bright Newton's ring radius
Locate a bright Newton's ring from its order, the wavelength and the lens curvature, such as order 3 with 589 nm light on a 1 m lens.
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Thin film constructive interference calculator
For 550 nm light on a film of index 1.38 with one phase reversal, the thinnest film that reinforces the reflection is 99.6376811594203 nm thick.
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Bragg law interplanar spacing calculator
Turns a diffraction peak into a lattice spacing: a Bragg angle of 20° with 1.5406 Å X-rays in first order gives planes 2.25220652945 Å apart.
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Coherence time calculator
Turns coherence length into time: light with a 3 m coherence length stays coherent for about 10 nanoseconds, the time it takes to cross that distance in vacuum.
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Luminous Intensity from Illuminance Calculator
Work out a lamp's candela from a simple lux reading: 125 lux measured 2 metres from a small source means 500 candela in that direction, as long as the meter…
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Stefan-Boltzmann radiant exitance calculator
A blackbody at 300 K emits 459.300328 W/m², and doubling the absolute temperature multiplies that by 16.
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Work Function from Threshold Wavelength Calculator
Enter a photoelectric cutoff of 500 nm and get the minimum energy an electron needs to leave the metal, in electronvolts and joules, plus the matching threshold…
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Fiber length from loss budget calculator
Find how far a fiber run can reach on its loss allowance: 7.5 dB spread over fiber losing 0.35 dB/km gives a theoretical maximum of 21.428571 km.
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Graded-index fiber mode count calculator
Get a quick mode budget for a graded-index fiber: a V-number of 20 supports about 100 guided modes, polarization included, using the large-V rule of V squared…
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Reciprocity shutter speed calculator for aperture stop changes
Close the aperture two stops at 1/125 s (0.008 s) and the shutter must stay open four times longer, 0.032 s.
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Sunny 16 rule shutter speed calculator for any film ISO
In bright sun at f/16, ISO 100 points to 1/100 s, and the nearest standard shutter setting is 1/125 s.
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Radiant intensity calculator
A source sending 12 W evenly through 3 sr has an average radiant intensity of 4 W/sr. Enter the power and the solid angle, choose how many decimals you want…
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Codominance cross ratio calculator
Two roan RW cattle produce calves in a 1:2:1 ratio, 25% red, 50% roan and 25% white, because a codominant heterozygote shows both alleles.
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Chi-square degrees of freedom genetics
A dihybrid 9:3:3:1 table has four phenotype classes and three degrees of freedom. Enter your class count and any estimated parameters to get the right number…
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Coefficient of relationship calculator
Full siblings share two pedigree paths of two links each, so their coefficient of relationship is 0.5, or 50%.
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Mutation-selection equilibrium calculator
See how common a hidden recessive allele can remain: with a mutation rate of 0.000001 and a selection coefficient of 0.01, the allele settles at 0.01, carriers…
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mRNA to protein length calculator
Know how long the protein will be from the message alone: a 300-nucleotide coding sequence holds 100 codons and gives a protein of 99 amino acids, because the…
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Bacterial exponential growth calculator
100 bacteria with a 20-minute generation time become 800 after 60 minutes: three doublings, an eightfold increase.
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Ligation insert:vector ratio calculator
Set up a ligation by molecules, not by mass: with 50 ng of a 3000 bp vector, a 500 bp insert and a 3:1 ratio, you add 25 ng of insert.
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PCR product yield copies calculator
See how far a PCR can go in theory: 100 starting copies after 30 cycles at 100% efficiency become 107,374,182,400 amplicon copies, about 1.073742 × 10¹¹.
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Biomass yield coefficient calculator
Find how much biomass each gram of substrate made: biomass rising from 0.5 to 4.5 while substrate falls from 20 to 2 gives 4 grams of cells from 18 grams…
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Serial dilution volumes calculator
A 1:10 series in 1000 µL tubes takes 100 µL of sample and 900 µL of diluent per tube; the calculator lists every tube with its source, both pipette volumes and…
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Logistic growth rate calculator
Get the instantaneous growth of a population that is filling its habitat: 50 individuals with an intrinsic rate of 0.1 and a carrying capacity of 100 add 2.5…
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Logistic growth calculator
See where a bounded population will stand: 50 individuals growing at 0.4 per year toward a carrying capacity of 1000 reach about three quarters of that ceiling…
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Species abundance proportions calculator
Counts of 40, 30, 20 and 10 trees give a total of 100 and shares of 0.4, 0.3, 0.2 and 0.1: the calculator turns raw tallies into the proportions that Shannon…
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Fertilizer blend ratio calculator
A 1,000 kg load of 10-10-10 needs 100 kg each of nitrogen, phosphate and potash, and this calculator works out how much urea, DAP, potash and filler deliver it.
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Finite population growth rate calculator
See how much a population multiplies between censuses: 100 animals counted one year and 120 the next give λ = 1.2, a 20% rise with r ≈ 0.1823.
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Leaf area index calculator
Compare a lawn, a wheat field and a forest on one scale: 6 m² of leaf over 2 m² of ground is a leaf area index of 3, a closed canopy.
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Grain adjusted weight calculator
Settle a grain ticket at the agreed moisture instead of the scale weight: 10000 kg of maize at 18% moisture holds 8200 kg of dry kernel, so at a 15% standard…
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Manure nutrient application calculator
Turn a manure lab sheet into a fertilizer credit: 10 tons per acre of manure testing 10, 8 and 12 lb per ton supplies 100 lb of N, 80 lb of P2O5 and 120 lb of…
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Dew point simple approximation calculator
Get the classic pocket estimate of dew point: 20 °C at 80 % relative humidity gives 16 °C, a 4-degree depression.
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Vapor pressure deficit calculator
At 25 °C and 60% relative humidity the vapor pressure deficit is just above 1.2 kPa: the pull with which the air draws water out of leaves.
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Altitude from pressure calculator
Turn a barometer reading into height: 900 hPa against a sea-level pressure of 1013.25 hPa puts you just under a kilometre up.
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Summer simmer index calculator
At 90 °F and 60% relative humidity, the summer simmer index lands in the discomfort band. It folds heat and humidity into one thermometer-like number for warm…
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Beaufort number to wind speed range
Turn a Beaufort force into the speed band forecasts mean: force 6 is a strong breeze of 22 to 27 knots, or 10.8 to 13.8 m/s.
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Freezing rain ice accretion calculator
Size the ice a storm leaves on a power line: 2 mm/h of freezing rain for 6 hours in a 10 m/s wind builds 7.33693981 mm of radial ice on a 25 mm conductor.
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UNEP aridity index calculator
Find how dry a place really is: 350 mm of rain against 1400 mm of potential evapotranspiration gives an aridity index of 0.25, a semi-arid climate.
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Rubidium-strontium radiometric age calculator
An Rb-Sr isochron slope of 0.02 corresponds to about 1.395 billion years, a typical Precambrian granite age, using the Steiger and Jäger 1977 decay constant.
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Natural gas carbon footprint calculator
Turn a gas bill into carbon dioxide: 100 therms of natural gas release 530.6 kg of CO2, using the EPA factor of 5.306 kg per therm.
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Manning open-channel velocity calculator
Enter a roughness of 0.013, a hydraulic radius of 1 m and a slope of 0.001, and Manning's formula returns the mean flow velocity in metres per second; switch to…
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Porosity from void ratio calculator
A void ratio of 0.8 gives a porosity of 0.444, about 44.4 percent voids, from n = e/(1+e). Enter either phase ratio and get the other back, with the…
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Air quality index from nitrogen dioxide
Convert a one-hour nitrogen dioxide reading into the US EPA air quality index: 53 ppb sits at the top of the Good band and gives AQI 50.
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Solar battery charge time calculator
A 100 Ah battery charged at 10 A through an 85% efficient path gets 8.5 A of effective current and refills in just under 12 hours.
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Fog stability index calculator
Judge radiation fog risk in one number: 8 °C at the surface, a 7 °C dew point and 10 °C at 850 hPa give an index of -2, a high risk.
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Frost risk index calculator
See whether tonight could freeze: an evening at 6 °C with a 1 °C dew point and 10 % cloud is expected to bottom out at 1.42 °C, a frost risk index of 32.25…
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Solar water heater energy savings
With 200 liters a day, a 40 °C rise and a solar fraction of 0.7, the daily heating load is just over 9 kWh and the collector covers 70% of it all year.
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Water heating energy calculator
Heating 50 liters of water by 40 °C takes 8342896 joules, just over 2 kWh or 1994 kilocalories. Water density and specific heat are built in, so you only enter…
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Temperature at depth calculator
Get a first estimate of how hot the ground is below you: 15 °C at the surface with a gradient of 25 °C per km gives 65 °C at 2000 m.
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Monthly thermal amplitude calculator
Twelve temperate months whose mean maxima run from 4 to 29 °C and minima from −3 to 17 °C give monthly amplitudes of 7 to 12 degrees and an annual average just…
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Basal area calculator
Turn a diameter tally into stand basal area: three sample trees averaging 30 cm at 400 stems per hectare give about 30.37 square metres per hectare.
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Cat chocolate toxicity calculator
Check how risky a chocolate theft was: 20 grams of milk chocolate eaten by a 4 kg cat gives 40 mg of theobromine, or 10 mg per kilogram, a negligible dose.
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Cell dilution calculator
From a stock of 2,400,000 cells/mL, reaching 500,000 cells/mL in 10 mL takes just over 2 mL of suspension and just under 8 mL of medium, a dilution factor of…
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Cow gestation calculator
A cow bred on 1 March 2026 is due around 9 December 2026, 283 days later, the textbook average for cattle.
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DNA to mRNA converter
Paste a coding-strand DNA sequence and every T becomes U: ATGC turns into AUGC, while A, C and G stay as they are.
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