The SI-system, unit converters, physical constants, drawing scales and more

Acceleration of Gravity and Newton's Second Law

Acceleration of gravity and Newton's Second Law - SI and Imperial units

Acceleration Units Converter

Convert between units of acceleration

Air Properties

Density, specific heat, thermal conductivity, expansion coefficient, kinematic viscosity and Prandtl's number - air temperature ranging -150 oC to 400 oC

Angle Converter

Convert between angle units

British Imperial System

A principal system of units

Buffer solutions

Definitions, explanations and examples of how to make buffer solutions

Circles - Circumferences and Areas

Area and circumferences of circles with diameters in inches

Conversion Chart - from Inches to mm

Convert fractional and/or decimal inches to metric mm - and vice versa

Convert Gallons of Water to Pounds

and vice versa

Decimal System Prefixes

Prefix names of multiples and submultiples of units

Density, Specific Weight and Specific Gravity

An introduction to density, specific gravity and specific weight - formulas with examples

Dimensionless numbers

Definitions and symbols for physical and chemical dimensionless quantities, with areas of application of the different numbers. Reynolds, Euler, Nusselt, Prandtl..... and many more

Drawing Scales

Commonly used scales for blueprint drawings


Usefulnes of a process

Electromagnetic Spectrum

Electromagnetic wavelengths and frequencies

Elements of the Periodic System

The elements of the periodic system with names, symbols, atomic numbers and weights, melting and boiling points, density, electronegativity and electron affinity, and electron configuration

Empirical Equations

Empirical equations or formulas


Mechanical, thermal, electrostatic, phase and chemical equilibrium

Exponents - Powers and Roots

Fractional and integer exponents laws

Flow Units Converter

Convert between volume flow units - gpm, liter/sec, cfm, m3/h - an online flow unit calculator

Heat Capacity

The heat capacity of a substance is the amount of heat required to change its temperature by one degree, and has units of energy per degree

Humid Air and the Ideal Gas Law

Pressure, temperature and volume for an ideal or perfect gas like air with water vapor - or moist air

Ideal Gas Law

The relations between volume, pressure, temperature and quantity of a gas, including definition of density of a gas.

Inches - Decimal Equivalents

Decimal equivalents of eights, sixteenths, thirty-seconds and sixty-fourths of an inch

Inches - Fractions and Decimal Equivalents

Inches - fractional and decimal equivalents

Inches to feet, yards and meters - Conversion Chart

Convert from inches to feet, yards and meters

Length Units Converter

Convert between common length units like meters, feet, inches, nautical miles and more


Rules of logarithms - log10 and loge for numbers ranging 1 to 1000

Mass and Weight

Mass and Weight - the Gravity Force

Mixtures, Solutions and Suspensions

The difference between mixtures, solutions and suspensions

Mole and Avagadro's Number

The mole is the SI base unit for amount of substance

Moment of Inertia

Moment of Inertia (Mass Moment of Inertia) depends on the mass of the object, its shape and its relative point of rotation - Radius of Gyration

Naming of inorganic binary compounds

Rules for naming inorganic ionic and covalent types of chemical compounds

Naming of organic compounds

Nomenclature rules for different groups of organic compounds and functional groups, together with examples of use of the rules

Natural Trigonometric Functions

Sine, Cosine and Tangent - Natural Trigonometric Functions

Non-ideal gas - Van der Waals equation and constants

Listing of van der Waals constants for more than 200 gases, used to correct for non-ideal behavior of gases caused by intermolecular forces and the volume occupied by the gas particles

Online Fuel Equivalents Calculator

Online calculator to compute fuels energy equivalents - oil and gas

Optical Distance Law

Distance and geometric dilution of light

Ounces and Pounds converted to Grams

Converting ounces (ozs.) and pounds (lbs.) to grams (g)

Parts per million - ppm

ppm - parts per million - commonly used as a unit of concentration

Periodic Table of Elements

The periodic table of the elements with atomic numbers

pH Definition - basic (alkaline) and acidic

Introduction to pH - acidic and basic (alkaline)

Physical Constants

Physical constants - SI Units


Introduction to pressure - psi and Pa - online pressure units converter

Pressure to Head - Unit Converter

Convert between pressure and head units - like lb/in2, atm, inches mercury, bars, Pa and more ..

Pressure Units - Online Converter

Convert between pressure units like Pa,  bar, atmosphere, pound square feet, psi and more

Properties and State

Concept of properties and state

Pumps, Fans and Turbines - Horsepower

British Horse Power in pumps, fans and turbines - and how to convert to other units


The radian - unit of angle measure - and angular velocity

Ratio and Proportion

The relative values between quantities - ratio and proportion

Real Numbers Algebra

Real numbers algebra - commutative law for addition, associative law for addition and more

SI System

An introduction to the SI-system

Solar System Constants

Sun, Earth and Moon constants

Solids - Volumes and Surfaces

Volume and surface of solids like rectangular prism, cylinder, pyramid, cone and sphere - online calculator


A measure of the maximum amount of a solute that can be dissolved in a solvent

Solutions, molarity and dilution

Definitions and examples of how to calculate molarity and prepare dilutions

Some Measuring Units

Some commonly used measuring units - gross, dozen, quire, sheets ..

Specific Heat - Online Unit Converter

Online specific heat converter with the most commonly used units

Standard state and enthalpy of formation, Gibbs free energy of formation, entropy and heat capacity

Definition and explanation of the terms standard state and standard enthalpy of formation, with listing of values for standard enthalpy and Gibbs free energy of formation, as well as standard entropy and molar heat capacity, of 370 inorganic compounds

STP - Standard Temperature and Pressure & NTP - Normal Temperature and Pressure

The definition of STP - Standard Temperature and Pressure and NTP - Normal Temperature and Pressure

Symbols Used to Denote a Chemical Reaction, Process or Condition

Explanation of symbols used as subscripts or superscripts to tell more about the type of chemical reaction, process or condition


Introduction to temperature - including Celsius, Fahrenheit, Kelvin and Rankine definitions - an online temperature converter

Thermodynamics key values internationally agreed

Internationally agreed, internally consistent, values for the thermodynamic properties (standard enthalpy of formation, entropy and [H°(298)-H°(0)]) of key chemical substances

Total and partial pressure - Dalton's law of partial pressures

How to calculate total pressure and partial pressures for gas mixtures from Ideal Gas Law

U.S. Gallons to U.K. Gallons, Cubic Feet and Cubic Meters - Converting Chart

Convert between U.S. liquid Gallons, U.K. liquid Gallons, Cubic Feet and Cubic Meters

Unit Converter with the most commonly used Units

Common converting units for Acceleration, Area, Density, Energy, Energy per unit mass, Force, Heat flow rate, Heat flux, Heat generation per unit volume and many more

USCS - United States Customary System Units

United States Customary System Units or Imperial Units

Vector Addition

Online vector calculator - add vectors with different magnitude and direction

Velocity Units Converter

Convert between common velocity and speed units - online converter

Volume Units Converter

Convert between common volume units like cubic meters, cubic feet, cubic inches and more

Water Content in Food and other Products

Water content before and after drying in food and other products cork, grain, soap, peat, wood and more

Water Pressure and Head

Pressure in pounds per square inch (psi) versus head in feet of water (fth2o)

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