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Use constants as starting values for thermodynamics, mechanics, fluids, heat transfer, and physics calculations.
Engineering notation reference
Engineering Constants Reference
Search common engineering constants, physical constants, mathematical constants, and reference values with symbols, units, and typical engineering use.
Searchable reference
Find engineering constants quickly
Filter the table by symbol, name, command, unit, drawing term, or engineering use case.
Watch out
Check precision and conditions
Some values are exact constants, while material and environmental values depend on temperature, pressure, and convention.
Reference table
Common engineering constants with units
| Constant | Symbol | Value | Units | Use |
|---|---|---|---|---|
| Acceleration due to gravity | 9.80665 | m/s2 | Weight, free fall, hydrostatics | |
| Avogadro constant | 6.02214076 x 1023 | mol-1 | Moles and particle count | |
| Boltzmann constant | 1.380649 x 10-23 | J/K | Thermal physics | |
| Density of water at 4 C | 1000 | kg/m3 | Fluids reference | |
| Earth radius | 6.371 x 106 | m | Geodesy and orbital estimates | |
| Elementary charge | 1.602176634 x 10-19 | C | Electrical charge | |
| Euler number | 2.718281828 | dimensionless | Exponential growth and decay | |
| Golden ratio | 1.6180339887 | dimensionless | Geometry | |
| Gravitational constant | 6.67430 x 10-11 | m3/(kg s2) | Gravitation | |
| Pi | 3.1415926535 | dimensionless | Circular geometry | |
| Planck constant | 6.62607015 x 10-34 | J s | Quantum physics | |
| Speed of light in vacuum | 2.99792458 x 108 | m/s | Waves, relativity, optics | |
| Standard atmosphere | 101325 | Pa | Pressure reference | |
| Stefan-Boltzmann constant | 5.670374419 x 10-8 | W/(m2 K4) | Radiation heat transfer | |
| Universal gas constant | 8.314462618 | J/(mol K) | Ideal gas law |
How to use
Practical notation checks
Copy carefully
symbol + meaning + units
A symbol is only useful when its meaning and units are clear in the surrounding equation or drawing note.
Avoid ambiguity
same symbol, different fields
Symbols such as E, G, R, and sigma can mean different things in different engineering domains.
Match the standard
notation follows context
Use notation that matches the drawing, report, coding, or calculation standard used by your team.
Search first
name, symbol, command, or unit
Use the search field to jump directly to the needed symbol, constant, or notation.
Definitions
Key notation concepts
Constant
A value treated as fixed for a calculation or reference context.
Exact constant
A defined value with no measurement uncertainty in the SI system.
Reference value
A useful value that may depend on conditions, such as water density or standard atmosphere.
Units
The dimensional basis needed before substituting a constant into an equation.
FAQ
Engineering Constants Reference questions
How should I use this reference?
Search by symbol, name, command, unit, or drawing term, then copy the value or use the meaning in your equation, report, drawing, or documentation.
Can I use these symbols directly in engineering drawings?
Use the symbols as a reference, but final drawings should follow the required ASME, ISO, company, or project drafting standard.
Why include searchable tables?
Search makes it faster to find a symbol by name, field, notation, command, or common engineering use instead of scanning a long list.
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