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 the author

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

Gas Collected Over Water Vapor Correction Calculator

Corrects the total gas pressure for water vapour when a gas is collected over water, then calculates moles from dry pres...

Basic

6,944 3.8 1 min

Physics

Stokes' Law Drag Force Calculator

Compute the viscous drag force on a small sphere moving slowly through a Newtonian fluid (low Reynolds number) using Sto...

Basic

24,280 4.2 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

15,786 3.9 1 min

Chemistry / Solutions

Boiling Point Elevation Calculator

Calculates the boiling point elevation of a solution using the van't Hoff factor, ebullioscopic constant and molality.

Basic

20,991 3.9 1 min

Chemistry / Solutions

Mole-Mass Conversion Calculator

Convert between mass (grams) and amount (moles) of a substance using its molar mass: n = m / M and m = n · M. Also repor...

Basic

7,130 4.5 1 min

Physics / Mechanics

Circular Orbit Period from Radius and Central Mass Calculator

Calculates orbital period T = 2π√(r³/GM), orbital velocity v = √(GM/r), and centripetal acceleration for a circular orbi...

Basic

8,477 4.0 1 min

Health

Macronutrient Split from Daily Calories Calculator

Converts calorie percentages for carbohydrates, protein, and fat into daily gram targets: carb 4 kcal/g, protein 4 kcal/...

Basic

20,386 4.1 1 min

Chemistry / Reactions

Heat of Reaction (Hess) Calculator

Compute the standard enthalpy of reaction ΔH_rxn from the standard formation enthalpies of up to two products and two re...

Basic

5,617 4.3 1 min

Chemistry

Dalton's Law Partial Pressure Calculator

Calculates partial pressures for up to four gas components in a mixture using Dalton's Law and mole fractions.

Basic

22,550 3.9 1 min

Sports / Swimming

Swimming Pace per 100 m / 100 yd Calculator

Converts total swim time and distance into pace per 100 m or 100 yd, and projects splits for any target race distance.

Basic

11,072 4.8 1 min

Chemistry

Born-Haber Cycle Lattice Enthalpy Calculator

Uses Hess's law via the Born-Haber cycle to calculate the lattice enthalpy of an ionic compound from standard thermochem...

Basic

8,738 3.9 1 min

Physics / Electricity

Joule Heating Resistor Power Calculator

Calculates electrical power dissipated as heat in a resistor from current and resistance, or voltage and resistance.

Basic

10,791 4.7 1 min

Showing 25 to 36 of 540 results

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Reviewed by Dr. Helena Ortiz

These calculators were technically reviewed by Dr. Helena Ortiz for accuracy.

Health / Body Metrics

Cockcroft-Gault Creatinine Clearance Calculator

Estimate creatinine clearance (a proxy for kidney function used in drug dosing) using the Cockcroft-Gault equation.

Basic

16,409 4.0 1 min

Chemistry / Solutions

Gas Density Calculator

Compute the density of an ideal gas at given pressure and temperature from its molar mass, using ρ = PM/(RT).

Basic

4,981 4.2 1 min

Physics / Electricity

Current Divider Calculator

Compute the current through one branch of a two-resistor parallel current divider from the total source current.

Basic

13,508 4.7 1 min

Biology / Microbiology

Population Doubling Time Calculator

Compute how long a population (or culture, or investment) takes to double at a constant exponential growth rate using th...

Basic

19,562 3.9 1 min

Physics / Mechanics

Velocity Calculator

Compute velocity from displacement and time, or solve for either one given the other two.

Basic

20,035 4.1 1 min

Health / Body Metrics

Steroid Dose Equivalence Calculator

Convert a dose of one corticosteroid into the equivalent dose of another, using standard glucocorticoid potency multipli...

Basic

14,581 4.2 1 min

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Dr. Helena Ortiz

Gas Collected Over Water Vapor Correction Calculator

Stokes' Law Drag Force Calculator

MLB On-Base + Slugging (OPS) Calculator

Boiling Point Elevation Calculator

Mole-Mass Conversion Calculator

Circular Orbit Period from Radius and Central Mass Calculator

Macronutrient Split from Daily Calories Calculator

Heat of Reaction (Hess) Calculator

Dalton's Law Partial Pressure Calculator

Swimming Pace per 100 m / 100 yd Calculator

Born-Haber Cycle Lattice Enthalpy Calculator

Joule Heating Resistor Power Calculator

Reviewed by Dr. Helena Ortiz

Cockcroft-Gault Creatinine Clearance Calculator

Gas Density Calculator

Current Divider Calculator

Population Doubling Time Calculator

Velocity Calculator

Steroid Dose Equivalence Calculator