General Engineering & Power Transmission Info

Our quick-reference guide for everything you need to know about torque, horsepower, speed, belting, gearing, inertia, and mechanical conversions used in power transmission applications, featuring integrated on-page calculators for fast metric and temperature conversions.

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Quick Reference Index
  1. Metric Conversions (Calculator)
  2. Temperature (Calculator)
  3. Basic Geometry
  4. Motion
  5. Force • Work • Torque
  6. Power
  7. Inertia
  8. Gearing
  9. Belting
  10. Overhung Load
  11. Electric Motors

 Metric Conversion Formulas & Calculator 

Metric Conversions Calculator
Inches ↔ Millimeters
mm = in × 25.4   |   in = mm ÷ 25.4
Rounded to 4 decimals where needed.
Feet ↔ Meters
m = ft × 0.3048   |   ft = m ÷ 0.3048
Rounded to 4 decimals where needed.
Pounds ↔ Kilograms
kg = lb ÷ 2.20462   |   lb = kg × 2.20462
Rounded to 4 decimals where needed.
Ounces ↔ Grams
g = oz × 28.3495   |   oz = g ÷ 28.3495
Rounded to 4 decimals where needed.
US Gallons ↔ Liters
L = gal × 3.78541   |   gal = L ÷ 3.78541
Rounded to 4 decimals where needed.
Horsepower ↔ Kilowatts
kW = HP × 0.746   |   HP = kW ÷ 0.746
Rounded to 4 decimals where needed.
Torque: ft·lb ↔ N·m
N·m = ft·lb × 1.35582   |   ft·lb = N·m ÷ 1.35582
Rounded to 4 decimals where needed.
Torque: in·lb ↔ N·m
N·m = in·lb × 0.112985   |   in·lb = N·m ÷ 0.112985
Rounded to 4 decimals where needed.
Pressure: PSI ↔ kPa
kPa = PSI × 6.89476   |   PSI = kPa ÷ 6.89476
Rounded to 4 decimals where needed.
Pressure: PSI ↔ bar
bar = PSI × 0.0689476   |   PSI = bar ÷ 0.0689476
Rounded to 4 decimals where needed.
Tip: You can type in either box — the other updates automatically.

 Temperature Conversion Formulas & Calculator 

Temperature Conversion Calculator
Fahrenheit → Celsius
°C = 5/9 × (°F − 32)
— °C
Celsius → Fahrenheit
°F = (1.8 × °C) + 32
— °F
Results are rounded to 2 decimals.

 Basic Geometry 

Circumference of a Circle Circumference = 3.1416 × Diameter
Diameter of a Circle Diameter = Circumference ÷ 3.1416

 Motion 

Speed Ratio Ratio = RPMHigh ÷ RPMLow
Belt Speed (Feet Per Minute) FPM = 0.262 × RPM × Diameter (inches)
Gear Ratio Ratio = Teeth of Gear ÷ Teeth of Pinion
Sprocket / Pulley Diameter Ratio Ratio = DiameterDriven ÷ DiameterDriver

 Force - Work - Torque 

Force (F) Given: Torque & Diameter F = (Torque × 2) ÷ Diameter
Torque (T) Given: Force & Diameter T = (Force × Diameter) ÷ 2
Diameter (Dia.) Given: Torque & Force Diameter = (2 × Torque) ÷ Force
Work Given: Force & Distance Work = Force × Distance
Chain Pull Given: Torque & Diameter Pull = (Torque × 2) ÷ Diameter

 Power 

Chain Pull Given: Horsepower & Speed (FPM) Pull = (33,000 × HP) ÷ Speed
Horsepower Given: Force & Speed (FPM) HP = (Force × Speed) ÷ 33,000
Horsepower (in-lb) Given: Torque (in-lb) & RPM HP = (Torque × RPM) ÷ 63,025
Horsepower (ft-lb) Given: Torque (ft-lb) & RPM HP = (Torque × RPM) ÷ 5,250
Torque (in-lb) Given: Horsepower & RPM Torque = (63,025 × HP) ÷ RPM
Torque (ft-lb) Given: Horsepower & RPM Torque = (5,250 × HP) ÷ RPM

 Inertia 

Accelerating Torque (ft-lb) Given: WK2, RPM, Time T = (WK2 × RPM) ÷ (308 × Time)
Accelerating Time (sec) Given: Torque, WK2, RPM t = (308 × Torque) ÷ (WK2 × RPM)
WK2 at Motor Given: WK2 at Load, Ratio WK2Motor = WK2Load ÷ Ratio2

 Gearing 

Gearset Centers Given: PD Gear & PD Pinion Centers = (PDGear + PDPinion) ÷ 2
Pitch Diameter (PD) Given: Teeth & Diametral Pitch (DP) PD = Teeth ÷ DP
Pitch Diameter (PD) Given: Teeth & Module PD = (Teeth × Module) ÷ 25.4
Diametral Pitch (DP) Given: Teeth & Pitch Diameter (PD) DP = Teeth ÷ PD
Module Given: PD & Teeth Module = (PD × 25.4) ÷ Teeth
Circular Pitch (CP) Given: PD & Teeth CP = (3.1416 × PD) ÷ Teeth
Circular Pitch (CP) Given: Diametral Pitch (DP) CP = 3.1416 ÷ DP
Number of Teeth Given: PD & DP Teeth = PD × DP
Number of Teeth Given: PD & Module Teeth = (PD × 25.4) ÷ Module
Tooth Depth (TD) Given: Diametral Pitch (DP) TD = 2.35 ÷ DP
Tooth Depth (TD) Given: Module TD = (2.35 × Module) ÷ 25.4

 Belting 

Effective Tension (Te) Given: T1 and T2 Te = T1 − T2
Effective Tension (Te) Given: HP, RPM, Radius (R) Te = (63,025 × HP) ÷ (RPM × R)
Total Belt Load (TL) Given: T1 and T2 TL = T1 + T2

 Overhung Load 

Overhung Load (OHL) Given: Torque & Diameter Diameter should be measured at the point of load application. OHL = (Torque × 2) ÷ Diameter
Overhung Load (OHL) Given: HP, RPM, Diameter, Belt Factor (f) Commonly used for belt-driven applications. OHL = (126,000 × f × HP) ÷ (Diameter × RPM)
Belt Factor (f) Select based on belt type Used only when calculating OHL from horsepower.
V-Belts f = 1.50
Flat Belts f = 2.50
Overhung Load (OHL) From Weight Applies when component weight is directly supported by the shaft. OHL = Weight

 Electric Motors 

Motor Speed (RPM) Given: Frequency (Hz) & Poles This is synchronous speed (actual RPM may be slightly lower due to slip). RPM = (120 × Hz) ÷ Poles
Single Phase Motor (HP) Given: Volts, Amps, PF, Efficiency Use PF and Efficiency as decimals (ex: 0.90). HP = (Volts × Amps × PF × Eff) ÷ 746
3-Phase Motor (HP) Given: Volts, Amps, PF, Efficiency 1.73 = √3 (3-phase multiplier). HP = (Volts × Amps × 1.73 × PF × Eff) ÷ 746
Motor Power (Watts) Given: Volts, Amps, PF, Efficiency Watts are input power; output depends on efficiency. Watts = Volts × Amps × PF × Eff