100+ Engineering Conversion Formulas | Complete Unit Guide

100+ Engineering Conversion Formulas

A categorized quick-reference guide covering the most commonly used unit conversion formulas across mechanical, civil, electrical, and thermal engineering disciplines.

1. Length / Distance Conversions

1. 1 inch (in) = 2.54 centimeters (cm)
2. 1 foot (ft) = 0.3048 meters (m)
3. 1 yard (yd) = 0.9144 meters (m)
4. 1 mile (mi) = 1.60934 kilometers (km)
5. 1 meter (m) = 3.28084 feet (ft)
6. 1 kilometer (km) = 0.62137 miles (mi)
7. 1 millimeter (mm) = 0.03937 inches (in)
8. 1 nautical mile = 1.852 kilometers (km)
9. 1 micron (μm) = 0.000001 meters (m)
10. 1 mil (thou) = 0.0254 millimeters (mm)

2. Area Conversions

11. 1 square foot (ft²) = 0.092903 square meters (m²)
12. 1 square meter (m²) = 10.7639 square feet (ft²)
13. 1 acre = 43,560 square feet (ft²)
14. 1 acre = 4,046.86 square meters (m²)
15. 1 hectare (ha) = 10,000 square meters (m²)
16. 1 square mile (mi²) = 2.58999 square kilometers (km²)
17. 1 square inch (in²) = 6.4516 square centimeters (cm²)
18. 1 square yard (yd²) = 0.83613 square meters (m²)

3. Volume Conversions

19. 1 US gallon (gal) = 3.78541 liters (L)
20. 1 liter (L) = 0.264172 US gallons (gal)
21. 1 cubic foot (ft³) = 28.3168 liters (L)
22. 1 cubic meter (m³) = 264.172 US gallons (gal)
23. 1 cubic meter (m³) = 35.3147 cubic feet (ft³)
24. 1 US quart (qt) = 0.946353 liters (L)
25. 1 barrel (oil, bbl) = 42 US gallons (gal)
26. 1 cubic inch (in³) = 16.3871 cubic centimeters (cm³)

4. Mass / Weight Conversions

27. 1 pound (lb) = 0.453592 kilograms (kg)
28. 1 kilogram (kg) = 2.20462 pounds (lb)
29. 1 US ton (short ton) = 907.185 kilograms (kg)
30. 1 metric ton (tonne) = 1,000 kilograms (kg)
31. 1 ounce (oz) = 28.3495 grams (g)
32. 1 metric ton = 1.10231 US short tons
33. 1 slug = 14.5939 kilograms (kg)
34. 1 grain = 0.0647989 grams (g)

5. Force Conversions

35. 1 pound-force (lbf) = 4.44822 newtons (N)
36. 1 newton (N) = 0.224809 pound-force (lbf)
37. 1 kilogram-force (kgf) = 9.80665 newtons (N)
38. 1 dyne = 0.00001 newtons (N)
39. 1 kip (1,000 lbf) = 4,448.22 newtons (N)
40. 1 poundal = 0.138255 newtons (N)

6. Pressure / Stress Conversions

41. 1 pound per square inch (psi) = 6,894.76 pascals (Pa)
42. 1 bar = 100,000 pascals (Pa)
43. 1 atmosphere (atm) = 101,325 pascals (Pa)
44. 1 atmosphere (atm) = 14.6959 psi
45. 1 pascal (Pa) = 0.000145038 psi
46. 1 torr = 133.322 pascals (Pa)
47. 1 bar = 14.5038 psi
48. 1 inch of mercury (inHg) = 3,386.39 pascals (Pa)

7. Energy / Work Conversions

49. 1 British thermal unit (BTU) = 1,055.06 joules (J)
50. 1 joule (J) = 0.000947817 BTU
51. 1 calorie (cal) = 4.184 joules (J)
52. 1 kilowatt-hour (kWh) = 3,600,000 joules (J)
53. 1 kilowatt-hour (kWh) = 3,412.14 BTU
54. 1 foot-pound (ft·lb) = 1.35582 joules (J)
55. 1 electronvolt (eV) = 1.60218 × 10⁻¹⁹ joules (J)
56. 1 therm = 100,000 BTU

8. Power Conversions

57. 1 horsepower (hp) = 745.7 watts (W)
58. 1 watt (W) = 0.00134102 horsepower (hp)
59. 1 kilowatt (kW) = 1.34102 horsepower (hp)
60. 1 BTU per hour (BTU/hr) = 0.293071 watts (W)
61. 1 metric horsepower (PS) = 735.499 watts (W)
62. 1 ton of refrigeration = 3,516.85 watts (W)

9. Torque Conversions

63. 1 pound-foot (lb·ft) = 1.35582 newton-meters (N·m)
64. 1 newton-meter (N·m) = 0.737562 pound-feet (lb·ft)
65. 1 pound-inch (lb·in) = 0.112985 newton-meters (N·m)
66. 1 kilogram-force meter (kgf·m) = 9.80665 newton-meters (N·m)

10. Temperature Conversions

67. Celsius to Fahrenheit: °F = (°C × 9/5) + 32
68. Fahrenheit to Celsius: °C = (°F − 32) × 5/9
69. Celsius to Kelvin: K = °C + 273.15
70. Fahrenheit to Kelvin: K = (°F − 32) × 5/9 + 273.15

11. Speed / Velocity Conversions

71. 1 mile per hour (mph) = 1.60934 kilometers per hour (km/h)
72. 1 kilometer per hour (km/h) = 0.621371 miles per hour (mph)
73. 1 meter per second (m/s) = 3.6 kilometers per hour (km/h)
74. 1 knot = 1.15078 miles per hour (mph)
75. 1 knot = 0.514444 meters per second (m/s)
76. 1 mile per hour (mph) = 0.44704 meters per second (m/s)

12. Angular Measurement Conversions

77. 1 radian (rad) = 57.2958 degrees (°)
78. 1 degree (°) = 0.0174533 radians (rad)
79. 1 revolution = 360 degrees (°)
80. 1 revolution per minute (RPM) = 0.10472 radians per second (rad/s)

13. Density Conversions

81. 1 pound per cubic foot (lb/ft³) = 16.0185 kilograms per cubic meter (kg/m³)
82. 1 kilogram per cubic meter (kg/m³) = 0.062428 pounds per cubic foot (lb/ft³)
83. 1 gram per cubic centimeter (g/cm³) = 1,000 kilograms per cubic meter (kg/m³)
84. 1 pound per gallon (lb/gal) = 119.826 kilograms per cubic meter (kg/m³)

14. Flow Rate Conversions

85. 1 gallon per minute (GPM) = 0.0630902 liters per second (L/s)
86. 1 cubic foot per minute (CFM) = 0.471947 liters per second (L/s)
87. 1 liter per second (L/s) = 15.8503 gallons per minute (GPM)
88. 1 cubic meter per hour (m³/hr) = 4.40287 gallons per minute (GPM)

15. Electrical Conversions

89. 1 kilowatt (kW) = 1,000 watts (W)
90. Ohm’s Law: Voltage (V) = Current (I) × Resistance (R)
91. Power Formula: Power (W) = Voltage (V) × Current (I)
92. 1 horsepower (electrical, hp) = 746 watts (W)
93. 1 megawatt (MW) = 1,000,000 watts (W)
94. 1 kilovolt-ampere (kVA) = 1,000 volt-amperes (VA)
95. 1 ampere-hour (Ah) = 3,600 coulombs (C)
96. 1 milliwatt (mW) = 0.001 watts (W)

16. Fuel Economy Conversions

97. Miles per gallon (mpg) to liters per 100 km: L/100km = 235.215 ÷ mpg
98. Liters per 100 km to miles per gallon: mpg = 235.215 ÷ (L/100km)
99. 1 mile per gallon (mpg) = 0.425144 kilometers per liter (km/L)
100. 1 kilometer per liter (km/L) = 2.35215 miles per gallon (mpg)

17. Time and Frequency Conversions

101. 1 hertz (Hz) = 1 cycle per second
102. 1 kilohertz (kHz) = 1,000 hertz (Hz)
103. 1 megahertz (MHz) = 1,000,000 hertz (Hz)
104. 1 minute = 60 seconds (s)
105. 1 hour = 3,600 seconds (s)

18. Stress and Moment of Inertia

106. 1 pound per square inch (psi) = 0.00689476 megapascals (MPa)
107. 1 megapascal (MPa) = 145.038 pounds per square inch (psi)
108. 1 kip per square inch (ksi) = 6.89476 megapascals (MPa)
109. Moment of Inertia (rectangular section): I = (b × h³) / 12, where b = base and h = height

19. Viscosity Conversions

110. 1 poise (P) = 0.1 pascal-seconds (Pa·s)
111. 1 centipoise (cP) = 0.001 pascal-seconds (Pa·s)
112. 1 stoke (St) = 0.0001 square meters per second (m²/s)

20. Thermal Conversions

113. 1 BTU per hour per square foot per °F (BTU/hr·ft²·°F) = 5.67826 watts per square meter per Kelvin (W/m²·K)
114. Thermal Conductivity: 1 BTU·in/(hr·ft²·°F) = 0.144228 W/(m·K)
115. Heat Transfer Formula: Q = m × c × ΔT, where Q = heat energy, m = mass, c = specific heat capacity, ΔT = temperature change

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How to Use This Guide

Each conversion factor above can be used directly as a multiplier. For example, to convert 10 pounds to kilograms: 10 lb × 0.453592 = 4.53592 kg. For formulas involving multiple variables (such as torque, heat transfer, or moment of inertia), plug in the known values in the specified units to solve for the missing quantity.

This reference is intended for quick lookups during design calculations, unit checks, and engineering coursework. For critical or safety-related engineering work, always verify conversion factors against an authoritative source such as NIST’s official guide to the International System of Units before finalizing any calculation.