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

Chemistry / Solutions

PPM and PPB Concentration Calculator

Convert the mass of a solute (in mg) per mass or volume of solution into parts-per-million (ppm) and parts-per-billion (...

basic

11,246 4.4 1 min

Chemistry

Second-Order Reaction Integrated Rate Law Calculator

Calculates concentration at time t and half-life for a second-order reaction from initial concentration and rate constan...

basic

17,973 4.2 1 min

Physics

Relativistic Velocity Addition Calculator

Combine two collinear velocities relativistically: u' = (u + v) / (1 + u · v / c²). Inputs are expressed as fractions of...

basic

16,955 4.7 1 min

Physics / Mechanics

Sound Intensity Level (Decibels) from Intensity Calculator

Compute the sound intensity level β (in decibels) from a sound's physical intensity I (W/m²) referenced to the threshold...

basic

12,495 5.0 1 min

Physics / Mechanics

Moment of Inertia — Solid Cylinder Calculator

Calculates the moment of inertia of a solid cylinder rotating about its central axis and the corresponding rotational ki...

basic

19,976 4.9 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

9,462 5.0 1 min

Chemistry / Solutions

Normality to Molarity Conversion Calculator

Converts normality N to molarity M using M = N / n, where n is the equivalence factor (number of H⁺, OH⁻, or electrons p...

basic

19,008 4.5 1 min

Physics / Mechanics

Kepler's Third Law Calculator

Compute the orbital period of a body in a Keplerian orbit from its semi-major axis and the mass of the central body, usi...

basic

22,636 4.5 1 min

Chemistry

Calorimetry (q = mcΔT) Calculator

Compute the heat absorbed or released by a substance using q = m · c · ΔT, given the mass, the specific heat capacity, a...

basic

14,274 4.9 1 min

Chemistry / Reactions

Faraday Electrolysis Calculator

Compute the mass of metal deposited (or evolved) at an electrode from the applied current, the time, the number of elect...

basic

16,659 4.3 1 min

Chemistry

Theoretical (Stoichiometric) Combustion Air for a Fuel Calculator

Compute the theoretical (stoichiometric) mass of air required to completely combust 1 kg of a solid or liquid fuel from...

basic

2,268 4.5 1 min

Chemistry

Gibbs Free Energy from Equilibrium Constant Calculator

Compute the standard Gibbs free-energy change ΔG° of a reaction from its thermodynamic equilibrium constant K and temper...

basic

20,928 4.6 1 min

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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

PPM and PPB Concentration Calculator

Second-Order Reaction Integrated Rate Law Calculator

Relativistic Velocity Addition Calculator

Sound Intensity Level (Decibels) from Intensity Calculator

Moment of Inertia — Solid Cylinder Calculator

Solubility in Common-Ion Solution from Ksp Calculator

Normality to Molarity Conversion Calculator

Kepler's Third Law Calculator

Calorimetry (q = mcΔT) Calculator

Faraday Electrolysis Calculator

Theoretical (Stoichiometric) Combustion Air for a Fuel Calculator

Gibbs Free Energy from Equilibrium Constant Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator