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

Motor Torque from Power and RPM Calculator

Calculates motor shaft torque from power and rotational speed. Also outputs angular velocity ω in rad/s. Essential for m...

basic

2,354 4.0 1 min

Chemistry

Iodine Value of Unsaturated Fat Calculator

Calculates the iodine value — grams of iodine (I₂) absorbed per 100 g of fat. Used to measure the degree of unsaturation...

basic

24,403 4.7 1 min

Finance / Investing

Bond Macaulay Duration from Coupon and YTM Calculator

Calculates Macaulay duration = Σ(t × PV(CF_t)) / Bond Price and modified duration = Macaulay / (1 + YTM/n) for a coupon-...

basic

20,400 4.8 1 min

Chemistry / Solutions

Buffer pH After Adding Strong Acid (Henderson–Hasselbalch) Calculator

Calculates the pH of a buffer after a known amount of strong acid is added, using the Henderson–Hasselbalch equation: pH...

basic

938 4.3 1 min

Chemistry

Salt Solution pH Classifier

Predict whether a salt produces an acidic, basic, or neutral solution by inputting the strength of the parent acid and p...

basic

22,460 4.0 1 min

Physics

De Broglie Matter Wavelength Calculator

Calculates the de Broglie wavelength of a particle from its mass and velocity, illustrating wave-particle duality.

basic

8,916 4.6 1 min

Statistics / Probability

Odds Ratio and Relative Risk from 2×2 Table Calculator

Calculates odds ratio OR = (a·d)/(b·c) and relative risk RR = (a/(a+b)) / (c/(c+d)) from a 2×2 exposure/outcome continge...

basic

15,233 3.9 1 min

Chemistry

Empirical Formula from Combustion-Analysis CO₂ and H₂O Calculator

Determine the empirical formula of an organic compound containing C, H, and (optionally) O from a combustion analysis: a...

basic

18,987 4.6 1 min

Chemistry

Volume of an Ideal Gas at Non-STP Conditions Calculator

Compute the volume of an ideal gas at a target pressure and temperature given its volume at a reference state, using the...

basic

14,710 4.2 1 min

Chemistry

van der Waals Real Gas Pressure Calculator

Compute the pressure of a real gas using the van der Waals equation P = nRT/(V − nb) − a·n²/V², with the gas-specific co...

basic

9,563 4.7 1 min

Physics

Refractive Index from Speed of Light Calculator

Calculates the refractive index of a medium from the speed of light in that medium. Also computes the critical angle for...

basic

19,101 4.5 1 min

Chemistry

Molar Solubility from K_sp Calculator

Compute the molar solubility s of a sparingly-soluble ionic salt from its solubility-product K_sp. Choose the dissolutio...

basic

8,081 4.7 1 min

Showing 205 to 216 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

4,965 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

15,826 4.9 1 min

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Dr. Helena Ortiz

Motor Torque from Power and RPM Calculator

Iodine Value of Unsaturated Fat Calculator

Bond Macaulay Duration from Coupon and YTM Calculator

Buffer pH After Adding Strong Acid (Henderson–Hasselbalch) Calculator

Salt Solution pH Classifier

De Broglie Matter Wavelength Calculator

Odds Ratio and Relative Risk from 2×2 Table Calculator

Empirical Formula from Combustion-Analysis CO₂ and H₂O Calculator

Volume of an Ideal Gas at Non-STP Conditions Calculator

van der Waals Real Gas Pressure Calculator

Refractive Index from Speed of Light Calculator

Molar Solubility from K_sp Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator