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

Physics

Stefan-Boltzmann Blackbody Power Calculator

Compute the radiated power of a thermal emitter from its emissivity, surface area, and absolute temperature, using P = ε...

basic

14,100 4.3 1 min

Chemistry / Reactions

Raoult's Law Calculator

Compute the partial vapor pressure of the solvent above an ideal solution from the mole fraction of the solvent and the...

basic

17,311 4.1 1 min

Chemistry

Mole-to-Mole Stoichiometry Calculator

Compute the moles of product B produced (or reactant B consumed) per moles of A using the balanced-equation coefficients...

basic

6,296 4.8 1 min

Finance

Marginal vs Effective Tax Rate Calculator

Calculates total income tax and effective tax rate using simplified progressive brackets (10%/22%/32%). Also shows margi...

basic

23,609 3.9 1 min

Sports / Swimming

Swim Training Weekly Volume and Yardage Calculator

Calculates total weekly swim volume (m and yards) from number of sessions, average sets, and distance per set. Also show...

basic

18,256 3.8 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

9,902 4.2 1 min

Chemistry / Solutions

Colligative Osmotic Pressure van't Hoff Extended Calculator

Calculates osmotic pressure using Π = cRT(1 + Bc), where c is the concentration, R = 8.314 J/(mol·K), T is temperature,...

basic

825 4.1 1 min

Physics / Mechanics

Mass-Spring Angular Frequency Calculator

Compute the natural angular frequency ω, ordinary frequency f, and period T of a Hookean mass-spring oscillator: ω = √(k...

basic

2,340 3.8 1 min

Physics

Hagen-Poiseuille Volumetric Flow Calculator

Compute the volumetric flow rate of an incompressible Newtonian fluid in laminar flow through a circular pipe using the...

basic

12,843 4.9 1 min

Physics / Mechanics

Stellar Parallax Distance Calculator

Compute the distance to a star from its annual parallax angle in arcseconds, using d (parsecs) = 1 / parallax_arcsec. Re...

basic

14,313 4.8 1 min

Physics

Wind Turbine Betz Power Output Calculator

Calculates the theoretical and actual power output of a wind turbine from wind speed, rotor diameter, air density, and p...

basic

9,457 4.9 1 min

Physics / Electricity

RL Series Circuit Current Build-Up Calculator

Compute the transient current in a series RL circuit driven by a DC source after the switch closes: i(t) = (V/R) · (1 −...

basic

10,572 4.5 1 min

Showing 469 to 480 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

Stefan-Boltzmann Blackbody Power Calculator

Raoult's Law Calculator

Mole-to-Mole Stoichiometry Calculator

Marginal vs Effective Tax Rate Calculator

Swim Training Weekly Volume and Yardage Calculator

Molarity from Mass and Solution Volume Calculator

Colligative Osmotic Pressure van't Hoff Extended Calculator

Mass-Spring Angular Frequency Calculator

Hagen-Poiseuille Volumetric Flow Calculator

Stellar Parallax Distance Calculator

Wind Turbine Betz Power Output Calculator

RL Series Circuit Current Build-Up Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator