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

Reaction Order from Initial-Rate Doubling-of-Concentration Experiment Calculator

Determine the order of a reaction with respect to a reactant A from two initial-rate experiments where [A] is changed (t...

Basic

19,641 4.5 1 min

Physics

Thin-Lens Magnification from Image and Object Distance Calculator

Compute the linear (transverse) magnification of an image formed by a thin lens or spherical mirror from the object dist...

Basic

4,880 4.6 1 min

Chemistry

Bond Enthalpy of Reaction from Bond Energies Calculator

Estimate the standard reaction enthalpy from average bond energies: ΔH_rxn ≈ Σ(bonds broken) − Σ(bonds formed). Enter th...

Basic

24,105 4.1 1 min

Chemistry

Percent Ionization of a Weak Acid Calculator

Compute the percent ionization of a weak monoprotic acid: % ionization = ([H⁺] / C₀) · 100, with [H⁺] ≈ √(Ka · C₀). Usef...

Basic

23,469 4.7 1 min

Everyday Life

Alcohol Unit Tracker Calculator

Calculates alcohol units in any drink from volume and ABV, and compares weekly total against recommended limits (UK guid...

Basic

22,460 3.9 1 min

Chemistry / Reactions

Bond Energy Reaction Calculator

Estimate the enthalpy change of a reaction from average bond energies: ΔH ≈ Σ (bonds broken in reactants) − Σ (bonds for...

Basic

5,779 4.3 1 min

Chemistry

Half-Life of a Zero-Order Reaction Calculator

Compute the half-life of a zero-order reaction A → products from the rate constant k (M·s⁻¹) and initial concentration [...

Basic

4,541 4.5 1 min

Physics

Electric Potential Energy of Two Point Charges Calculator

Calculates the electric potential energy U = k·q₁·q₂/r between two point charges and the electric force F = k·q₁·q₂/r²....

Basic

12,277 4.7 1 min

Chemistry / Solutions

Osmotic Pressure from Molarity and Temperature Calculator

Calculates osmotic pressure using the van't Hoff equation Π = i·M·R·T, where i is the van't Hoff factor (1 for non-elect...

Basic

25,024 4.8 1 min

Chemistry / Solutions

Molarity from Mass and Solution Volume Calculator

Compute the molar concentration of a solution directly from the mass of solute (in grams), its molar mass, and the final...

Basic

9,568 4.2 1 min

Chemistry / Solutions

Mole Fraction to Mass Percent (Binary Mixture) Calculator

Convert the mole fraction of component A in a binary mixture to mass-percent (and vice-versa for component B), given the...

Basic

7,103 4.0 1 min

Physics

Satellite Orbital Period Calculator

Compute the orbital period of a satellite in a circular orbit around a chosen body (Earth, Moon, Mars) from its altitude...

Basic

3,182 3.9 1 min

Showing 493 to 504 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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Dr. Helena Ortiz

Reaction Order from Initial-Rate Doubling-of-Concentration Experiment Calculator

Thin-Lens Magnification from Image and Object Distance Calculator

Bond Enthalpy of Reaction from Bond Energies Calculator

Percent Ionization of a Weak Acid Calculator

Alcohol Unit Tracker Calculator

Bond Energy Reaction Calculator

Half-Life of a Zero-Order Reaction Calculator

Electric Potential Energy of Two Point Charges Calculator

Osmotic Pressure from Molarity and Temperature Calculator

Molarity from Mass and Solution Volume Calculator

Mole Fraction to Mass Percent (Binary Mixture) Calculator

Satellite Orbital Period 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