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

Electron Kinetic Energy from Accelerating Voltage Calculator

Calculates KE = q·V for a particle accelerated through potential difference V. For an electron, q = 1.602×10⁻¹⁹ C. Also...

basic

8,167 4.3 1 min

Physics

Roche Limit Calculator

Compute the Roche limit (rigid-body approximation) — the distance at which a satellite will be torn apart by tidal force...

basic

17,681 5.0 1 min

Chemistry

Specific Rotation and Optical Activity Calculator

Converts observed optical rotation α into specific rotation [α] using the formula [α] = α / (l · c), where l is the path...

basic

23,888 4.0 1 min

Physics

Apparent vs Absolute Magnitude Calculator

Convert between apparent magnitude m and absolute magnitude M of a star using the distance modulus m − M = 5 · log10(d /...

basic

5,784 4.7 1 min

Physics / Electricity

RLC Bandwidth from Resonant Frequency and Q Calculator

Compute the −3 dB bandwidth Δf of an RLC resonant circuit: Δf = f₀ / Q, where f₀ is the resonant frequency and Q is the...

basic

16,105 4.1 1 min

Chemistry / Solutions

ppm to Molarity Conversion Calculator

Convert a parts-per-million concentration of a solute (assumed numerically equal to mg/L in dilute aqueous solutions) to...

basic

2,506 4.2 1 min

Sports / Swimming

Swim Split Time per 100m from Total Time and Distance Calculator

Calculates average 100m swim split time = total_seconds / (distance_m / 100), and pace per 50m lap. Useful for open-wate...

basic

5,782 4.8 1 min

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

1,317 4.7 1 min

Chemistry

PPM ↔ mg/L Conversion Calculator

Convert between parts-per-million (ppm) by mass and mg/L for an aqueous solution of given density: mg/L = ppm · density_...

basic

6,084 4.7 1 min

Chemistry / Solutions

Mass Percent Solution Calculator

Compute the mass percent of a solute in a solution from the mass of solute and the mass of solvent. Reports % (m/m) and...

basic

19,417 4.8 1 min

Everyday Life

Sale Discount & Final Price Calculator

Calculates the discounted final price, savings amount, and effective discount percentage for a sale item.

basic

16,181 4.1 1 min

Chemistry / Solutions

Van 't Hoff Osmotic Pressure Calculator

Calculates osmotic pressure using van 't Hoff's law from solute molarity, van 't Hoff factor, and temperature.

basic

9,124 3.8 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

4,965 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

Electron Kinetic Energy from Accelerating Voltage Calculator

Roche Limit Calculator

Specific Rotation and Optical Activity Calculator

Apparent vs Absolute Magnitude Calculator

RLC Bandwidth from Resonant Frequency and Q Calculator

ppm to Molarity Conversion Calculator

Swim Split Time per 100m from Total Time and Distance Calculator

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

PPM ↔ mg/L Conversion Calculator

Mass Percent Solution Calculator

Sale Discount & Final Price Calculator

Van 't Hoff Osmotic Pressure Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator