Biology Formulas

Action Potential Formula

Reference for the Hodgkin-Huxley equations describing neural action potentials, the electrical impulses that carry signals through the nervous system.

Population Doubling Time Formula

Calculate how long it takes a population to double using t_d = ln(2)/r. Learn the doubling time formula with worked examples.

Renal Clearance Formula

The renal clearance formula calculates how efficiently the kidneys filter a substance from blood. Includes GFR, creatinine clearance, and worked examples.

DNA Replication Rate Formula

Reference for DNA replication rate formulas. Covers replication forks, nucleotide incorporation rates, and how cells copy billions of base pairs per hour.

Lotka-Volterra Equations

The Lotka-Volterra equations model predator-prey population dynamics, showing how two species cycle in size over time. Includes worked examples.

Blood Volume Calculator — Nadler Formula (Men and Women)

Reference for the Nadler formula for total blood volume from height and weight. Separate equations for men and women with results in liters and mL/kg.

Fick's Law of Diffusion

Calculate the rate of diffusion using Fick's first law: J = -D(dC/dx). Learn how concentration gradients drive molecular movement.

Gompertz Growth Model

Calculate population or tumor growth using the Gompertz model, which accounts for exponential slowdown as carrying capacity is approached.

Henderson-Hasselbalch Equation

Reference for the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). Enter pKa and concentrations for bicarbonate, phosphate, or any acid buffer.

Nernst Equation for Membrane Potential

Calculate the equilibrium potential across a cell membrane for a specific ion using the Nernst equation. Essential for neuroscience.

Nerve Conduction Velocity

Calculate nerve conduction velocity with v = d/t. Learn how neurologists measure the speed of electrical signals along nerves.

Allometric Scaling Formula

Allometric scaling laws relate body mass to metabolic rate, lifespan, and other traits. Learn the power law Y = aM^b with examples.

Alveolar Gas Equation

The alveolar gas equation calculates oxygen pressure in the lungs. Learn the PAO₂ formula with clinical examples and applications.

Blood Oxygen Dissociation (Hill Equation)

The Hill equation models how hemoglobin binds oxygen. Learn the oxygen-hemoglobin dissociation curve formula with worked examples.

BMI Formula

Body Mass Index formula for metric and imperial units. Learn how to calculate BMI with worked examples and interpretation tables.

Cardiac Output Formula

Cardiac output (CO = HR times SV) measures blood pumped per minute. Reference formula with normal ranges, clinical significance, and step-by-step examples.

Carrying Capacity and Logistic Growth

Reference for logistic growth dN/dt = rN(1-N/K) and carrying capacity K. Includes worked examples for wildlife populations, bacteria, and ecosystem limits.

Cell Division Rate Formula

Calculate cell division rate and generation time using the formula N = N0 x 2^n. Understand mitotic rate with worked examples.

Cellular Respiration Equation

Reference for C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP cellular respiration. Covers glycolysis, Krebs cycle, and electron transport chain with net ATP per glucose.

Doubling Time Formula

Calculate how long it takes a population or quantity to double using the doubling time formula t = ln(2)/r. With worked examples.

Logistic Growth Equation

The logistic growth equation dN/dt = rN(1-N/K) models population growth that slows as it approaches the environment carrying capacity.

Michaelis-Menten Equation

The Michaelis-Menten equation V = Vmax[S]/(Km+[S]) describes enzyme kinetics and how reaction rate depends on substrate concentration.

Osmotic Pressure (Van't Hoff Equation)

The Van't Hoff equation calculates osmotic pressure from solute concentration and temperature. Key to biology and chemistry.

Photosynthesis Rate Formula

Understand the photosynthesis equation and factors that affect its rate. Includes light intensity, CO2 concentration, and temperature effects.

Punnett Square and Genetics

Predict offspring genotypes and phenotypes using Punnett squares for dominant, recessive, codominant, and X-linked traits with probability percentages.

Allele Frequency Formula

Calculate allele frequency from genotype counts using Hardy-Weinberg equilibrium. Returns p and q allele frequencies for population genetics analysis.

Bacterial Growth Formula

Calculate bacterial population size after binary fission using N = N0 × 2^n. Returns cell count after n generations with doubling time inputs for microbiology.

Hardy-Weinberg Equation

Predict allele and genotype frequencies in a stable population. The foundation of population genetics and evolution studies.

Michaelis-Menten Equation

Reference for the Michaelis-Menten equation v = Vmax[S] / (Km + [S]). Covers Km, Vmax, Lineweaver-Burk plot, and enzyme inhibition types.

Population Growth Formula

Calculate exponential population growth using the continuous growth model. Used in ecology, demographics, and microbiology.