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

Mole Fraction from Mass Composition Calculator

Converts mass composition of a binary mixture into mole fractions from component masses and molar masses.

Basic

2,572 4.7 1 min

Chemistry / Solutions

Common-Ion Effect Solubility Calculator

Compute the new molar solubility of a 1:1 salt MA in a solution that already contains a common-ion concentration [A⁻], u...

Basic

8,226 4.4 1 min

Chemistry / Solutions

Raoult's Law Vapor Pressure Mixture Calculator

Calculates the total vapor pressure of an ideal binary liquid mixture using Raoult's Law from mole fractions and pure co...

Basic

16,949 4.7 1 min

Everyday Life

Gravel Volume (Cubic Yards) from Area and Depth Calculator

Calculates the volume of gravel required to cover a rectangular area to a specified depth: volume (yd³) = (length × widt...

Basic

16,734 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

23,294 4.8 1 min

Everyday Life

Fuel Cost & Savings Commute Calculator

Calculates the annual fuel cost of a daily commute and potential savings from reducing trips, carpooling, or switching t...

Basic

19,229 4.1 1 min

Physics

Centrifugal Pump Specific Speed Nq Calculator

Calculates the specific speed (Nq) of a centrifugal pump to identify pump type (radial, mixed, axial) from speed, flow,...

Basic

24,315 5.0 1 min

Physics / Electricity

Electric Potential from a Point Charge Calculator

Compute the electric potential V (volts) at distance r from a point charge q, taking V = 0 at infinity: V = k · q / r, w...

Basic

23,313 4.4 1 min

Physics / Electricity

Internal Resistance Terminal Voltage Calculator

Calculates terminal voltage of a real battery or power source from EMF, internal resistance, and load current.

Basic

3,140 4.0 1 min

Chemistry

Bomb Calorimetry Enthalpy of Combustion Calculator

Calculates the molar internal energy and enthalpy of combustion from calorimeter heat capacity, temperature rise, sample...

Basic

15,081 4.5 1 min

Chemistry / Solutions

Boiling Point Elevation (Molal) Calculator

Calculates boiling point elevation from molal concentration and the ebullioscopic constant, and reports the new boiling...

Basic

6,190 3.9 1 min

Everyday Life

Date Difference in Days, Weeks, Months, and Years Calculator

Given the difference in days between two dates, converts to weeks, approximate months (÷30.44), and years (÷365.2425).

Basic

18,743 4.4 1 min

Showing 445 to 456 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

Mole Fraction from Mass Composition Calculator

Common-Ion Effect Solubility Calculator

Raoult's Law Vapor Pressure Mixture Calculator

Gravel Volume (Cubic Yards) from Area and Depth Calculator

Empirical Formula from Combustion-Analysis CO₂ and H₂O Calculator

Fuel Cost & Savings Commute Calculator

Centrifugal Pump Specific Speed Nq Calculator

Electric Potential from a Point Charge Calculator

Internal Resistance Terminal Voltage Calculator

Bomb Calorimetry Enthalpy of Combustion Calculator

Boiling Point Elevation (Molal) Calculator

Date Difference in Days, Weeks, Months, and Years 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