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

Physics

AC Circuit RLC Impedance Calculator

Calculates impedance, inductive reactance, capacitive reactance, and phase angle for a series RLC circuit at a given fre...

Basic

1,556 4.0 1 min

Physics

Specific Heat Capacity Energy Transfer Calculator

Calculates the heat energy transferred to or from a substance using Q = mcΔT. Enter mass, specific heat capacity, and te...

Basic

10,848 4.0 1 min

Chemistry

Catalytic Rate Enhancement from Lowered Activation Energy Calculator

Compute the factor by which a catalyst speeds up a reaction at temperature T, given that the activation energy drops by...

Basic

4,162 4.7 1 min

Chemistry / Reactions

Limiting Reagent Calculator (Two Reagents)

Compare two reagents in a balanced reaction by their (moles ÷ coefficient) ratio to identify the limiting reagent and th...

Basic

5,371 5.0 1 min

Math / Percentage

Integer Prime Factorisation Calculator

For integers up to ~10^6, determines whether n is prime and outputs the prime factorisation as p₁^e₁ × p₂^e₂ … by trial...

Basic

23,385 4.2 1 min

Physics

Electric Potential from Point Charge and Distance Calculator

Calculates the electric potential V = k·q/r at a distance r from a point charge q, where k = 8.9875×10⁹ N·m²/C². Also co...

Basic

21,800 4.0 1 min

Chemistry

Multistage Solvent-Extraction Residue Calculator

Compute the fraction of solute remaining in the aqueous phase after n batchwise extractions with a fresh portion of orga...

Basic

11,051 3.9 1 min

Physics

Terminal Velocity from Weight and Drag Calculator

Computes terminal velocity v_t = √(2mg / (ρ · A · C_d)), the speed at which drag equals weight and acceleration is zero.

Basic

9,518 3.8 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

6,995 4.3 1 min

Chemistry

Atom Economy of a Chemical Reaction Calculator

Calculates atom economy = (MW of desired product / sum of MWs of all products) × 100%. A higher atom economy means less...

Basic

14,932 3.9 1 min

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

16,863 4.0 1 min

Chemistry / Solutions

Osmotic Pressure π = iMRT Calculator

Calculates osmotic pressure and equivalent osmolarity of a solution from molarity, van't Hoff factor, and temperature.

Basic

2,706 4.0 1 min

Showing 133 to 144 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

AC Circuit RLC Impedance Calculator

Specific Heat Capacity Energy Transfer Calculator

Catalytic Rate Enhancement from Lowered Activation Energy Calculator

Limiting Reagent Calculator (Two Reagents)

Integer Prime Factorisation Calculator

Electric Potential from Point Charge and Distance Calculator

Multistage Solvent-Extraction Residue Calculator

Terminal Velocity from Weight and Drag Calculator

Wind Turbine Betz Power Output Calculator

Atom Economy of a Chemical Reaction Calculator

Tidal Force on a Test Body from a Distant Mass Calculator

Osmotic Pressure π = iMRT 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