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 / Mechanics

Time Dilation Calculator

Compute the dilated time observed in a stationary frame for a moving clock, given the proper time and the speed as a fra...

basic

1,856 4.2 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

13,277 4.5 1 min

Chemistry

Reaction Quotient Q from Concentrations Calculator

Calculates Qc for a general reaction aA + bB ⇌ cC + dD as Qc = [C]^c[D]^d / ([A]^a[B]^b), then compares to K to determin...

basic

23,444 4.4 1 min

Physics / Mechanics

Pendulum Length from Desired Period Calculator

Compute the length needed for a simple pendulum to swing with a desired period (small-angle approximation): L = T² · g /...

basic

21,984 4.7 1 min

Chemistry

Enthalpy of Vaporisation from Two Temperature–Pressure Points Calculator

Solves the integrated Clausius–Clapeyron equation: ln(P₂/P₁) = −ΔH_vap/R × (1/T₂ − 1/T₁) for ΔH_vap in kJ/mol.

basic

1,909 4.3 1 min

Chemistry

Mole Fraction from Partial Pressures (Dalton's Law) Calculator

Compute the mole fraction of each component in an ideal-gas mixture from up to four partial pressures using Dalton's law...

basic

1,151 4.6 1 min

Physics

Archimedes Buoyancy Force Calculator

Compute the buoyant force on an object submerged (or partially submerged) in a fluid using F_b = ρ_fluid · V · g, and th...

basic

20,093 4.5 1 min

Physics

Asteroid Impact Energy Calculator

Compute the kinetic energy released when a spherical asteroid of given diameter, density, and impact speed strikes a pla...

basic

24,828 4.6 1 min

Physics

Gravitational Time Dilation Calculator

Compute the gravitational time-dilation factor t/t₀ = √(1 − 2GM / (r·c²)) for a clock at distance r from a spherically s...

basic

19,333 4.4 1 min

Physics

Euler Column Buckling Critical Load Calculator

Calculates the Euler critical (buckling) load for a slender column from Young's modulus, second moment of area, effectiv...

basic

10,830 4.4 1 min

Chemistry

Critical Temperature and Pressure from van der Waals Constants Calculator

Calculates the critical temperature T_c = 8a/(27Rb) and critical pressure P_c = a/(27b²) of a real gas from its van der...

basic

12,408 4.8 1 min

Chemistry / Solutions

Osmotic Pressure from Molarity and Temperature Calculator

Calculates osmotic pressure using the van't Hoff equation Π = i·M·R·T, where i is the van't Hoff factor (1 for non-elect...

basic

4,040 4.2 1 min

Showing 241 to 252 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

Time Dilation Calculator

Integer Prime Factorisation Calculator

Reaction Quotient Q from Concentrations Calculator

Pendulum Length from Desired Period Calculator

Enthalpy of Vaporisation from Two Temperature–Pressure Points Calculator

Mole Fraction from Partial Pressures (Dalton's Law) Calculator

Archimedes Buoyancy Force Calculator

Asteroid Impact Energy Calculator

Gravitational Time Dilation Calculator

Euler Column Buckling Critical Load Calculator

Critical Temperature and Pressure from van der Waals Constants Calculator

Osmotic Pressure from Molarity and Temperature Calculator

Reviewed by Dr. Helena Ortiz

Equilibrium Constant Calculator

Length Converter

Combined Gas Law Calculator

Capacitance Calculator

pOH Calculator

Carbon Footprint Calculator