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.
Flash distance from guide number
Know where to stand before you shoot: a metric guide number of 36 at f/8 lights a subject correctly at 4.5 metres, in the same unit as the guide number on your…
Free · Runs in your browser
Optical path length calculator
Light crossing 0.25 m of material with a refractive index of 1.5 covers an optical path of 0.375 m: distance times index, shown step by step.
Free · Runs in your browser
Single-mode fiber cutoff wavelength calculator
A fiber with a 4.1 µm core radius and an NA of 0.14 turns single-mode above 1499.60431032 nm. Enter the radius and numerical aperture to check a design or a…
Free · Runs in your browser
Optical etendue calculator
Multiply source area by solid angle to get etendue: 0.0001 m² of emitter spreading into 0.02 sr gives 0.000002 m²·sr, a value that no lossless lens or mirror…
Free · Runs in your browser
Allee effect threshold calculator
See if a population is above its critical minimum: 40 animals with a threshold of 20 and carrying capacity of 100 grow by 480 per unit of time, a growing…
Free · Runs in your browser
AT to GC Ratio Calculator for DNA Base Counts
Enter four base counts and see how AT compares with GC: 30 adenine, 30 thymine, 20 guanine and 20 cytosine give 60 against 40, a ratio of 1.5 or 3:2, with 60…
Free · Runs in your browser
Beer Lambert concentration calculator
Turn a spectrophotometer reading into concentration: absorbance 0.75 with an extinction coefficient of 15000 and a 1 cm path gives 0.00005 mol/L, or 50 µmol/L.
Free · Runs in your browser
Bradford protein calculator
Turn a Bradford reading into protein concentration: absorbance 0.42 on a curve with slope 0.035 and intercept 0.05 gives just over ten and a half, in the units…
Free · Runs in your browser
Chilling hours calculator
Of eight hourly readings, five fell below 7.2 °C, so the orchard logged 5 chilling hours. Paste your hourly temperatures, pick the threshold, and see whether…
Free · Runs in your browser
Codon Usage Fraction Calculator for Gene Codon Counts
If a gene has 18 TTT and 12 TTC codons, both encoding phenylalanine, TTT accounts for 0.6 of that amino acid's codons.
Free · Runs in your browser
Dilution for a countable plate calculator
A sample at about 250,000,000 CFU/mL, plated at 0.1 mL, falls in a 30 to 300 colony range at a 1:100,000 dilution, with about 250 colonies expected.
Free · Runs in your browser
Dilution to target OD calculator
Bringing a culture from OD 1.8 down to 0.3 in 50 mL is a sixfold dilution: one part culture to five parts fresh medium.
Free · Runs in your browser
DNA helical turns calculator from base pairs
A 1,050 base-pair fragment makes 100 helical turns, using the common B-form average of 10.5 base pairs per turn.
Free · Runs in your browser
Dry matter intake calculator
25 kg of fresh feed at 40% dry matter supplies 10 kg of dry matter a day. Enter the daily as-fed weight and the feed's dry matter percentage in kilograms, grams…
Free · Runs in your browser
dsDNA mass to molar concentration calculator
A 5,000 bp plasmid weighs about 3,300,000 g/mol at 660 g/mol per base pair, so 50 ng/µL of it becomes a molar figure in µM, nM and pM.
Free · Runs in your browser
dsDNA ng/µL calculator from A260 absorbance
An A260 of 0.24 measured on a tenfold dilution means 120 ng/µL in the original sample: 50 ng/µL per absorbance unit times the dilution.
Free · Runs in your browser
Egg Incubation Hatch Date Calculator by Bird Species
Chicken eggs set on 1 March 2026 should hatch around 22 March 2026, after the standard 21 days. Pick the species and the set date to label trays, plan lockdown…
Free · Runs in your browser
Fertilizer NPK rate per hectare calculator
Supplying 120 kg/ha of nitrogen from a product with 20% nitrogen takes 600 kg/ha of it; the calculator checks phosphorus and potassium too and picks the rate…
Free · Runs in your browser
Fish stocking density calculator
Multiply pond size by the stocking rate you picked and get a count ready for the order: 1000 m² at 2 fish per m² means 2000 fish.
Free · Runs in your browser
Forage allowance calculator
Compare grazing pressure fairly across paddocks and herds: 6800 kg of usable dry matter on 4 ha for 40 animals of 450 kg means 18000 kg of live weight to feed…
Free · Runs in your browser
Bacterial Generation Time Calculator
Get the time one bacterial generation takes: 6 generations in 180 minutes means 30 minutes per generation, or 2 generations per hour.
Free · Runs in your browser
Crop harvest index calculator
See how much of a crop's above-ground growth ends up as harvest: 4500 kg per hectare of grain from 12000 kg per hectare of biomass is a harvest index of 0.375…
Free · Runs in your browser
Home range density calculator
Turn a telemetry or survey summary into one comparable figure: 24 animals sharing a combined 12 km² of home range means 2 individuals per km², also shown per…
Free · Runs in your browser
Importance value index calculator for plant species
Sum up how numerous, widespread and dominant a plant species is in one survey: Quercus alba at 35.5% density, 42.25% frequency and 28.75% dominance scores 106.5…
Free · Runs in your browser
Irrigation run time calculator
Know how long to leave the water on: putting 25 mm on 800 m² at 40 L per minute takes 20000 litres and 500 minutes of run time, ready for a controller or a…
Free · Runs in your browser
Life Table Survivorship Calculator
Standardize a cohort life table in one step: if 1000 animals start and 920, 760, 410 and 0 remain at each later age, survivorship reads 92%, 76%, 41% and 0.
Free · Runs in your browser
Lime requirement calculator
Go from a lab report to a lime order: a buffer pH of 6.2 with a 6.5 target calls for 3.64 tons of pure calcium carbonate per acre, or 36.4 tons for a 10-acre…
Free · Runs in your browser
Livestock daily water requirement
Size troughs and tanks before the animals arrive: 40 dairy cows at 100 litres each and 120 sheep at 8 litres each drink 4960 litres a day between them.
Free · Runs in your browser
Additive Map Distance Calculator with Double Crossover Correction
Join two map intervals in a known A-B-C order: 12 cM plus 8 cM gives 20 cM, while double crossovers with a coefficient of coincidence of 0.75 bring the…
Free · Runs in your browser
Molar absorptivity calculator
Get the extinction coefficient straight from your spectrophotometer reading: an absorbance of 0.75 at 0.000025 mol/L in a 1 cm cuvette gives 30000 L per mole…
Free · Runs in your browser
Most probable number (MPN)
Turn a row of positive and negative tubes into a density: a 5-3-1 result from three dilutions of 5 tubes each becomes an MPN per 100 mL, with the classic Thomas…
Free · Runs in your browser
DNA Nanograms to Copies Calculator by Base-Pair Length
Know how many molecules sit in your tube: 10 ng of a 3000 bp double-stranded DNA is about 3.04148523 billion copies, using 660 g per mole per base pair and the…
Free · Runs in your browser
DNA concentration from A260 calculator for DNA and RNA
Turn a spectrophotometer reading into a concentration you can pipette from: an A260 of 0.25 for double-stranded DNA diluted 20 times is 250 µg/mL, the same as…
Free · Runs in your browser
OD600 to CFU calculator
Turn a spectrophotometer reading into a viable cell estimate: an OD600 of 0.5 with a factor of 8 × 10⁸ CFU/mL per OD unit gives 4 × 10⁸ CFU/mL.
Free · Runs in your browser
Oligo nmol to µg calculator
Convert an oligo's nanomole yield into micrograms from its real base composition: 1 nmol of the DNA oligo ATCG, with a molecular weight of 1252.81 g/mol, is…
Free · Runs in your browser
Pasture carrying capacity calculator
Budget the grass before you stock it: 120 acres yielding 2,500 lb of dry matter per acre, at 30% utilization, feed 28 whole animals eating 26 lb a day for 120…
Free · Runs in your browser
Pedigree combined probability calculator
When more than one parental pairing can lead to the same offspring outcome, the routes are added correctly: 0.5 × 0.4 × 0.25 gives 0.05, a second route adds…
Free · Runs in your browser
Petersen–Chapman population estimate
Mark 200 animals, catch 150 later and find 20 with marks: the classic Petersen ratio says 1500, while the Chapman adjustment gives a slightly lower, less biased…
Free · Runs in your browser
Pond Fish Biomass Calculator
Know how much fish your pond holds: 2,500 fish averaging 0.45 kg each weigh 1,125 kg in total, the starting point for feeding plans, stocking reviews and…
Free · Runs in your browser
Population density calculator for habitat area or volume
Turn a field count into a density you can report: 240 individuals in 12 square kilometres give 20 individuals per square kilometre.
Free · Runs in your browser
Population Exponential Growth Calculator
Project a population while resources are not yet limiting: 1200 individuals at a continuous rate of 0.03 per year for 10 years grow by a factor of 1.349859, a…
Free · Runs in your browser
Population percent change calculator
Compare two censuses in one step: a town that grew from 10,000 to 12,500 residents gained 2,500 people, a 25% increase.
Free · Runs in your browser
PPM solution preparation calculator
Weigh the right amount of solute: 2 L of a 250 PPM solution with the default density of 1 kg/L needs 500 mg, or 0.5 g.
Free · Runs in your browser
Probability all offspring are the same sex calculator
In a family of 4, the chance that all children share one sex is 2 in 16, or 12.5%, because all of one sex and all of the other both count.
Free · Runs in your browser
Protein net charge calculator
See how charged your peptide is at a given pH: at pH 7.4, a peptide with 3 lysines, 2 arginines, 4 aspartates and 2 glutamates, among others, carries a net…
Free · Runs in your browser
Probability of two recessive traits
Two AaBb parents have a 1 in 16 chance, 0.0625 or 6.25%, of an offspring that shows both recessive traits, because 1/4 at each locus multiplies to 1/16.
Free · Runs in your browser
Protein purification calculator
Judge a purification step with two numbers: total activity falling from 12,000 to 7,800 units means 65% recovery, and specific activity rising from 2.5 to 18.75…
Free · Runs in your browser
Recombination Frequency Calculator for Two-Point Crosses
Enter 184 recombinant offspring out of 1000 scored and the recombination frequency is 18.4 %, with the 816 non-recombinants shown alongside, so a two-point…
Free · Runs in your browser
Rule of 70 Population Calculator
A population growing 2 % a year doubles in about 35 years: the rule of 70 turns a constant annual growth rate into a doubling time for lessons, community…
Free · Runs in your browser
Secondary Production Calculator for Population Biomass
With 120 units of biomass from growth and 30 from reproduction over an interval of 12, secondary production is 150 and the rate 12.5 per time unit, split 80 %…
Free · Runs in your browser
Seeding rate from spacing calculator
Rows 75 cm apart, hills every 25 cm and 2 seeds per hill need 106667 seeds per hectare: the calculator turns a field layout into a seed quantity for buying seed…
Free · Runs in your browser
Simpson index calculator
Four species with 10, 20, 5 and 15 individuals give lambda 0.3 and a Gini–Simpson diversity of 0.7: enter your counts and get Simpson's D, its complement…
Free · Runs in your browser
Single-tube dilution factor calculator
Bring 0.25 mL of sample to 5 mL total and the dilution factor is 20: the calculator also gives the 4.75 mL of diluent to add and the 0.05 sample fraction, one…
Free · Runs in your browser
Species Richness Count Calculator
Six observations of Oak, Pine, Oak, Birch, pine and Willow give a species richness of 4: paste your list and the calculator removes repeats, ignores…
Free · Runs in your browser
Specific growth rate mu calculator
Biomass rising from 0.12 to 0.48 in 3 hours is a fourfold increase: 2 generations with a doubling time of 1.5 hours.
Free · Runs in your browser
Thermal z-value calculator
If D drops from 5 to 0.5 when the process temperature rises from 110 to 120 °C, the z-value is 10: enter two temperature and D pairs to get z for lethality…
Free · Runs in your browser
Total Row Length Calculator
2.5 hectares planted at 0.75 m between rows hold 33.333 kilometres of crop row: the calculator divides the planted area by the row spacing so you can size seed…
Free · Runs in your browser
Trophic energy transfer calculator
If producers store 10000 kcal, only 1000 reach the herbivores at the classic 10 % efficiency: the calculator multiplies energy by the transfer fraction for each…
Free · Runs in your browser
Two-trait combined probability calculator
A 0.75 chance for one trait and 0.25 for another give a 0.1875 chance, or 18.75 %, that the same offspring shows both: the calculator applies the product rule…
Free · Runs in your browser
Weaning Weight Ratio Calculator for Contemporary Groups
Shows how one young animal measures up to its group: at 268 against a group average of 249, the ratio is 107.63 and it ranks first of 5.
Free · Runs in your browser