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

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

Health

Lung Age from FEV1 Spirometry Calculator

Estimates a patient's "lung age" from measured FEV1 and reference predicted FEV1 to motivate smoking cessation.

basic

7,227 4.9 1 min

Statistics / Probability

Bayes Theorem Posterior Update Calculator

Applies Bayes' theorem to update a prior probability with new evidence, outputting the posterior probability and likelih...

basic

4,181 4.6 1 min

Physics

Curved Mirror Image Distance and Magnification Calculator

Solves the mirror equation for concave (positive f) or convex (negative f) mirrors: 1/f = 1/d_o + 1/d_i. Returns image d...

basic

18,106 4.5 1 min

Chemistry

Fugacity Coefficient from van der Waals Equation Calculator

Calculates the van der Waals fugacity coefficient φ = exp[(b/(Vm−b)) − (2a/(RT·Vm))], where a and b are VdW constants, f...

basic

15,795 4.8 1 min

Physics

Lensmaker's Equation Focal Length Calculator

Compute the focal length of a thin lens from the refractive index of the lens material and the radii of curvature of the...

basic

20,167 4.6 1 min

Physics

Compound Microscope Magnification Calculator

Compute the total magnification of a compound microscope from the objective magnification (e.g. 10×, 40×, 100×) and the...

basic

21,249 4.0 1 min

Chemistry

Bomb Calorimetry Enthalpy of Combustion Calculator

Calculates the molar internal energy and enthalpy of combustion from calorimeter heat capacity, temperature rise, sample...

basic

5,738 4.8 1 min

Statistics

Log-Normal Distribution μ & σ Calculator

Calculates the PDF, CDF, mean, median, mode, and variance of a log-normal distribution from its log-scale parameters μ a...

basic

3,358 4.9 1 min

Physics / Electricity

Inductive Reactance Calculator

Compute the inductive reactance X_L of an inductor at a given AC frequency: X_L = 2π · f · L. Reports the impedance magn...

basic

6,443 4.2 1 min

Chemistry

Van der Waals Real Gas Equation Calculator

Calculates pressure of a real gas using the van der Waals equation from volume, temperature, moles, and the gas-specific...

basic

7,971 4.6 1 min

Chemistry

Standard Cell Potential from Half-Reaction Potentials Calculator

Calculates the standard cell potential E°_cell = E°_cathode − E°_anode from the standard reduction potentials of two hal...

basic

7,140 4.1 1 min

Chemistry

Beer-Lambert Absorbance & Concentration Calculator

Calculates absorbance, molar absorptivity, path length, or concentration using the Beer-Lambert law. Converts absorbance...

basic

6,260 4.9 1 min

Showing 433 to 444 of 504 results

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Reviewed by Dr. Helena Ortiz

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

Chemistry / Reactions

Equilibrium Constant Calculator

Compute the equilibrium constant K_c from the concentrations of two products (with stoichiometric coefficients 1) divide...

basic

5,060 4.0 1 min

Conversions / Length

Length Converter

Convert between meters, kilometers, miles, feet, inches, and yards.

Featured basic

4,964 4.2 1 min

Chemistry / Solutions

Combined Gas Law Calculator

Find the missing pressure, volume, or temperature using the combined gas law for a fixed amount of gas.

basic

5,360 4.2 1 min

Physics / Electricity

Capacitance Calculator

Compute the capacitance of a parallel-plate capacitor from plate area, plate separation, and the dielectric constant.

basic

12,524 4.1 1 min

Chemistry / Solutions

pOH Calculator

Compute pOH from hydroxide ion concentration and the matching pH at 25 °C.

basic

18,221 4.2 1 min

Ecology / Carbon Footprint

Carbon Footprint Calculator

Estimate your annual personal CO₂e footprint from home energy, driving, flying, and diet — with adjustable emission fact...

Featured basic

15,825 4.9 1 min

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Dr. Helena Ortiz

Lung Age from FEV1 Spirometry Calculator

Bayes Theorem Posterior Update Calculator

Curved Mirror Image Distance and Magnification Calculator

Fugacity Coefficient from van der Waals Equation Calculator

Lensmaker's Equation Focal Length Calculator

Compound Microscope Magnification Calculator

Bomb Calorimetry Enthalpy of Combustion Calculator

Log-Normal Distribution μ & σ Calculator

Inductive Reactance Calculator

Van der Waals Real Gas Equation Calculator

Standard Cell Potential from Half-Reaction Potentials Calculator

Beer-Lambert Absorbance & Concentration Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator