Featured contributor PhD Applied Physics; former research associate at a national metrology lab.

Dr. Helena Ortiz

Senior Reviewer, Science & Engineering

0 calculators 0 articles Member since Jun 2026

About the author

Helena is the senior technical reviewer for physics, chemistry, and unit-conversion calculators. She is the last pair of eyes on every formula — checking constants, units, and edge cases against primary sources and standards bodies.

She holds a PhD in Applied Physics and previously held a research post at a national metrology lab.

Areas of expertise

Physics Chemistry Unit conversion Measurement standards

Education & credentials

BSc Physics — Universidad Complutense de Madrid
PhD Applied Physics — Stanford University

Chemistry

Competitive Enzyme Inhibition Velocity Calculator

Calculates reaction velocity under competitive enzyme inhibition using the Michaelis–Menten equation with an apparent K_...

Basic

20,641 4.7 1 min

Physics / Mechanics

Lunar Phase on Date Calculator

Compute the Moon's phase, age in days, and illuminated fraction for any date, plus the next new- and full-moon dates. Us...

Basic

12,837 4.6 1 min

Statistics / Probability

Type II Error Rate (Beta) from Power Calculator

Calculates type II error rate β = 1 − power, type I error rate α, and the four outcomes of a hypothesis test with their...

Basic

1,318 4.2 1 min

Physics

Electron Kinetic Energy from Accelerating Voltage Calculator

Calculates KE = q·V for a particle accelerated through potential difference V. For an electron, q = 1.602×10⁻¹⁹ C. Also...

Basic

3,958 4.2 1 min

Chemistry

Radiometric Dating Age from Isotope Ratio Calculator

Calculates the age of a sample from the remaining fraction of parent isotope: t = ln(N₀/N) / λ = t½ × ln(N₀/N) / ln 2. S...

Basic

1,041 3.8 1 min

Physics

Hydrostatic Pressure at Depth Calculator

Compute the absolute pressure at a depth h below the surface of a fluid of density ρ, given the pressure at the free sur...

Basic

12,921 4.5 1 min

Chemistry

Nuclear Binding Energy & Mass Defect Calculator

Calculates nuclear mass defect and binding energy (total and per nucleon) from proton/neutron counts and actual nuclear...

Basic

6,548 4.6 1 min

Chemistry

Enthalpy of Vaporisation from Two Temperature–Pressure Points Calculator

Solves the integrated Clausius–Clapeyron equation: ln(P₂/P₁) = −ΔH_vap/R × (1/T₂ − 1/T₁) for ΔH_vap in kJ/mol.

Basic

3,288 4.4 1 min

Chemistry

Compressibility Factor Z from Real-Gas P, V, n, T Calculator

Compute the compressibility factor Z = PV / (nRT) for a real gas given pressure (atm), volume (L), moles, and temperatur...

Basic

23,240 4.2 1 min

Statistics

Statistical Power & Type II Error Calculator

Calculates the statistical power of a one-sample z-test from effect size, sample size, and significance level.

Basic

19,882 3.8 1 min

Chemistry / Solutions

Solubility in Common-Ion Solution from Ksp Calculator

For a salt AB dissolving in a solution already containing [B] = c₀, calculates the new molar solubility s where Ksp = s(...

Basic

17,994 4.0 1 min

Chemistry / Reactions

Theoretical Yield Calculator

Compute the theoretical yield of a product (in grams) from the mass of a single limiting reagent and the stoichiometric...

Basic

2,428 4.0 1 min

Showing 421 to 432 of 540 results

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Reviewed by Dr. Helena Ortiz

These calculators were technically reviewed by Dr. Helena Ortiz for accuracy.

Health / Body Metrics

Cockcroft-Gault Creatinine Clearance Calculator

Estimate creatinine clearance (a proxy for kidney function used in drug dosing) using the Cockcroft-Gault equation.

Basic

16,409 4.0 1 min

Chemistry / Solutions

Gas Density Calculator

Compute the density of an ideal gas at given pressure and temperature from its molar mass, using ρ = PM/(RT).

Basic

4,981 4.2 1 min

Physics / Electricity

Current Divider Calculator

Compute the current through one branch of a two-resistor parallel current divider from the total source current.

Basic

13,508 4.7 1 min

Biology / Microbiology

Population Doubling Time Calculator

Compute how long a population (or culture, or investment) takes to double at a constant exponential growth rate using th...

Basic

19,562 3.9 1 min

Physics / Mechanics

Velocity Calculator

Compute velocity from displacement and time, or solve for either one given the other two.

Basic

20,035 4.1 1 min

Health / Body Metrics

Steroid Dose Equivalence Calculator

Convert a dose of one corticosteroid into the equivalent dose of another, using standard glucocorticoid potency multipli...

Basic

14,581 4.2 1 min

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Browse categories

Dr. Helena Ortiz

Competitive Enzyme Inhibition Velocity Calculator

Lunar Phase on Date Calculator

Type II Error Rate (Beta) from Power Calculator

Electron Kinetic Energy from Accelerating Voltage Calculator

Radiometric Dating Age from Isotope Ratio Calculator

Hydrostatic Pressure at Depth Calculator

Nuclear Binding Energy & Mass Defect Calculator

Enthalpy of Vaporisation from Two Temperature–Pressure Points Calculator

Compressibility Factor Z from Real-Gas P, V, n, T Calculator

Statistical Power & Type II Error Calculator

Solubility in Common-Ion Solution from Ksp Calculator

Theoretical Yield Calculator

Reviewed by Dr. Helena Ortiz

Cockcroft-Gault Creatinine Clearance Calculator

Gas Density Calculator

Current Divider Calculator

Population Doubling Time Calculator

Velocity Calculator

Steroid Dose Equivalence Calculator