ENGINEERING FORMULA LIBRARY

Verified Engineering Formula Library

Fundamental mechanical equations across 9 categories derived from Shigley, Machinery's Handbook, Roark's Formulas, and ISO/ASME standards. Every equation includes derivation steps, symbols, and unit conventions.

13 formulas
9 categories
13 linked calculators

Strength of Materials

Fundamental stress, strain, and deflection equations for beams, shafts, and structural elements.

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EQU-001

Beam Bending Stress (σ = My/I Flexure Equation)

Calculate maximum beam bending stress (σ = My/I = M/S) and flexural stress distribution per Euler-Bernoulli beam theory with step-by-step derivation.

beam bending stressbending stress formulaflexural stress formula+7

Related:

beam-deflectionshaft-bending-torsionshaft-design-basics+2
EQU-002

Torsional Shear Stress in Shafts (τ = Tr/J Formula)

Calculate maximum torsional shear stress (τ = Tr/J = 16T/πd³) and polar moment of inertia for solid and hollow circular shafts under applied torque.

torsional shear stresstorsional shear stress formulashaft shear stress+6

Related:

shaft-diametershaft-bending-torsionshaft-design-basics

Machine Design

Combined loading criteria, fatigue analysis, and sizing equations per ASME and Shigley methods.

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EQU-003

ASME Shaft Sizing Formula (ASME B106.1M Fatigue)

Standard ASME B106.1M transmission shaft diameter equation under combined steady torque and cyclic bending fatigue using the ASME DE-Goodman criterion.

ASME shaft sizingASME shaft diameter formulaASME B106.1M+5

Related:

shaft-diametershaft-bending-torsionshaft-design-basics

Mechanics

Kinematics, dynamics, power transmission, and rotational motion relationships.

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EQU-004

Torque, Speed & Power Relation (P = Tω = 2πNT/60)

Calculate rotational power, motor torque, and shaft speed (RPM) across SI (kW, N·m) and Imperial (HP, lbf·ft) engineering units.

torque power relationtorque power speed formulatorque RPM power+7

Related:

shaft-diametershaft-bending-torsionshaft-design-basics+1

Fluid Mechanics

Pipe flow, head loss, friction factors, and fluid power equations.

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Thermodynamics

State equations, gas laws, and thermodynamic property relationships.

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Manufacturing

Forming, machining, and fabrication calculation formulas.

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Materials

Elasticity, plasticity, and material property relationships.

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Fasteners

Bolt preload, torque, joint analysis, and thread engagement formulas.

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Bearings

Fatigue life, load ratings, and selection criteria per ISO 281.

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TRANSPARENT EQUATIONS, ASSUMPTIONS, AND REFERENCES

Built for Professional Mechanical Design

  1. Standard-Sourced

    Every formula cites Shigley, Machinery's Handbook, Roark's, or ISO/ASME standards.

  2. Symbol Defined

    All variables include symbol, unit conventions, and applicability limits.

  3. Derivation Linked

    Step-by-step derivation paths connect to textbook chapter references.

  4. Calculator Linked

    Related design calculators provide immediate numerical evaluation.

Need a formula derivation that isn't listed? Check our calculators or submit a request via GitHub.