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

Tidal Force on a Test Body from a Distant Mass Calculator

Compute the differential gravitational pull (tidal force) exerted by a distant mass M on a small body of mass m and char...

basic

1,736 4.1 1 min

Physics / Mechanics

SHM Displacement, Velocity & Amplitude Calculator

Calculates displacement, velocity, acceleration, and kinetic/potential energy of a simple harmonic oscillator at any ins...

basic

8,674 4.4 1 min

Everyday Life

Coffee Caffeine Content and Half-Life Calculator

Calculates remaining caffeine in your system after a given time using the caffeine half-life of approximately 5.7 hours....

basic

21,842 4.2 1 min

Health

AUDIT-C Alcohol Use Disorder Screening Calculator

Calculates the AUDIT-C score from 3 questions: frequency of drinking (0–4), typical number of drinks (0–4), frequency of...

basic

7,641 4.3 1 min

Chemistry

Faraday Electrolysis: Charge to Moles Deposited Calculator

Uses Faraday's laws of electrolysis to calculate moles deposited: n = Q / (z · F), where Q is charge in coulombs, z is i...

basic

8,727 4.7 1 min

Chemistry

Water Hardness from Ca²⁺ and Mg²⁺ Calculator

Compute total water hardness expressed as mg/L of CaCO₃ from calcium (mg/L) and magnesium (mg/L) measurements: Hardness...

basic

14,409 4.4 1 min

Physics / Electricity

Electric Field from a Point Charge Calculator

Compute the magnitude of the electric field a distance r from a point charge Q, using Coulomb's constant k = 8.988 × 10⁹...

basic

20,874 4.4 1 min

Finance

Gordon Growth Perpetuity & Terminal Value Calculator

Calculates the terminal (continuing) value of a firm or project using the Gordon growth perpetuity formula from the next...

basic

4,305 4.7 1 min

Sports

MLB On-Base + Slugging (OPS) Calculator

Calculates On-Base Percentage (OBP), Slugging Percentage (SLG), and OPS for a baseball hitter from plate appearance stat...

basic

7,261 4.4 1 min

Sports

Reactive Strength Index (RSI) from Jump Height and Contact Time Calculator

Calculates RSI = jump height (m) / ground contact time (s). Values >2.5 are elite; 1.5–2.5 are good; <1.5 needs improvem...

basic

19,763 4.8 1 min

Chemistry

Latent Heat of Fusion Energy Calculator

Compute the energy Q required to melt a substance at its melting point from the mass and the substance-specific latent h...

basic

20,942 4.5 1 min

Finance

Discounted Cash Flow DCF Terminal Value Calculator

Calculates Gordon Growth terminal value and its present value for a DCF analysis. Terminal value typically represents 60...

basic

287 4.5 1 min

Showing 217 to 228 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

Tidal Force on a Test Body from a Distant Mass Calculator

SHM Displacement, Velocity & Amplitude Calculator

Coffee Caffeine Content and Half-Life Calculator

AUDIT-C Alcohol Use Disorder Screening Calculator

Faraday Electrolysis: Charge to Moles Deposited Calculator

Water Hardness from Ca²⁺ and Mg²⁺ Calculator

Electric Field from a Point Charge Calculator

Gordon Growth Perpetuity & Terminal Value Calculator

MLB On-Base + Slugging (OPS) Calculator

Reactive Strength Index (RSI) from Jump Height and Contact Time Calculator

Latent Heat of Fusion Energy Calculator

Discounted Cash Flow DCF Terminal Value Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator