Biology Calculators

Cardiac Output and Hemodynamics Calculator

Calculate cardiac output, cardiac index, and systemic vascular resistance from heart rate, stroke volume, body surface area, and mean arterial pressure.

Goldman Equation Membrane Potential

Calculate resting membrane potential using the Goldman-Hodgkin-Katz equation. Enter ion permeabilities and concentrations for K+, Na+, and Cl- at body temperature.

LD50 Dose-Response Curve Calculator

Estimate response probability at any dose using the log-logistic model. Enter LD50 and Hill slope to plot the sigmoid dose-response curve for any compound.

Metabolic Water Calculator

Calculate water produced by oxidizing carbohydrates, fats, and proteins. Shows why desert animals like camels and kangaroo rats can survive without drinking free water.

Neuron Conduction Velocity Calculator

Calculate action potential conduction speed for myelinated and unmyelinated nerve fibers from axon diameter. Compare propagation time over any nerve length.

Oxygen-Hemoglobin Dissociation Calculator

Calculate hemoglobin oxygen saturation at any partial pressure using the Hill equation. Adjust P50 and cooperativity to model shifts from pH, temperature, and 2,3-DPG.

Allometric Scaling Calculator

Estimate basal metabolic rate from body mass using Kleiber's law. Compare BMR across animal sizes and see how the 3/4 power law scales from mice to elephants.

ATP Yield from Cellular Respiration

Calculate ATP produced from glucose metabolism. Compare aerobic respiration (32 ATP) versus anaerobic glycolysis (2 ATP) with a stage-by-stage breakdown chart.

Nernst Potential Calculator

Calculate the equilibrium membrane potential for Na+, K+, Ca2+, Cl- and custom ions. Enter intra- and extracellular concentrations and temperature in Celsius.

Species-Area Relationship Calculator

Estimate species richness from habitat area using MacArthur and Wilson's S = cA^z equation. Calculate how habitat loss reduces biodiversity in any ecosystem.

Bacterial Growth and Doubling Time Calculator

Calculate bacterial doubling time, growth rate constant, and number of generations from initial and final cell counts or OD600 absorbance readings.

DNA Ancestry Percentage by Generation

Calculate what percentage of DNA you share with each generation of ancestors, from parents to great-great-great-grandparents and beyond.

Leaf Transpiration Rate Calculator

Calculate leaf transpiration rate from stomatal conductance, leaf temperature, and relative humidity. Returns results in mol/sq m/s and mm per day.

Michaelis-Menten Enzyme Kinetics Calculator

Calculate enzyme reaction velocity using Michaelis-Menten kinetics. Find Km and Vmax from data points using Lineweaver-Burk double reciprocal analysis.

Monohybrid Cross Calculator

Calculate the expected offspring ratios for a single-trait Mendelian genetic cross. Enter parent genotypes to see phenotype and genotype probabilities.

Osmotic Pressure Calculator (van t Hoff)

Calculate osmotic pressure using the van t Hoff equation. Enter solute concentration, temperature, and van t Hoff factor to get pressure in atm, kPa, and mmHg.

Photosynthesis Rate and Light Response Calculator

Calculate net photosynthesis rate at any light intensity using the rectangular hyperbola model. Find light compensation and saturation points.

Species Diversity Index Calculator (Shannon-Wiener)

Calculate Shannon-Wiener diversity index, Simpson index, species richness, and Pielou evenness from species count data. Ecology biodiversity tool.

Growing Degree Units Calculator

Calculate growing degree units (GDUs) per day for corn, soybeans, wheat, and other crops. Includes modified corn GDU method and crop stage reference table.

Phylogenetic Distance Calculator

Calculate evolutionary distance between DNA sequences using p-distance and Jukes-Cantor correction. Returns similarity, substitutions, and divergence time.

Protein Molar Extinction Coefficient Calculator

Calculate molar extinction coefficient from Trp, Tyr, and Cys content. Estimate protein concentration from A280 absorbance using the Pace formula.

Punnett Square Calculator (Dihybrid Cross)

Calculate dihybrid cross outcomes from alleles for two traits. Get phenotype ratios, genotype frequencies, and offspring probabilities for Mendelian genetics.

ΔΔCT Fold Change Calculator

Calculate gene expression fold change using the ddCT method for qPCR. Compare treatment vs control groups with reference gene normalization.

DNA Melting Temperature (Tm) Calculator

Calculate the melting temperature of DNA primers and oligonucleotides. Supports both basic (Wallace rule) and nearest-neighbor thermodynamic methods.

GC Content Calculator

Calculate the GC content percentage of any DNA or RNA sequence. Shows nucleotide composition, complementary strand, and molecular weight estimate.

Hardy-Weinberg Equilibrium Calculator

Calculate expected genotype frequencies under Hardy-Weinberg equilibrium. Determine allele frequencies, test population assumptions, and explore genetics.

Lotka-Volterra Predator-Prey Model Calculator

Simulate predator-prey population dynamics using the classic Lotka-Volterra equations. See how predator and prey populations oscillate over time.

PCR Annealing Temperature Calculator

Calculate optimal PCR annealing temperature from primer Tm values. Uses Wallace rule and nearest-neighbor thermodynamics for specific, efficient amplification.

Plant Vapor Pressure Deficit (VPD) Table

Look up vapor pressure deficit (VPD) for any temperature and humidity combination. Find if your grow environment is in the optimal zone for each growth stage.

Population Growth Rate Calculator

Model exponential and logistic population growth. Calculate doubling time, carrying capacity effects, and project future population from growth rates.

Protein Molecular Weight Calculator

Estimate protein molecular weight from amino acid sequence or composition. Returns weight in Daltons and kilodaltons for biochemistry and SDS-PAGE.

qPCR Efficiency Calculator

Calculate qPCR amplification efficiency from a dilution series. Determine slope, R² value, and efficiency percentage to validate your real-time PCR assay.

SEIR Epidemic Spread Model Calculator

Simulate disease spread using the SEIR model (Susceptible, Exposed, Infectious, Recovered). Adjust R0, incubation period, and recovery time.