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Unit Conversion Formula in Mechanical, Civil and Electrical

February 11, 2026
3 Min
By - MiT

In design and engineering career fields, correct units are required to ensure accurate results. The aesthetic appearance of a drawing or machine can be perfect, but if the units are incorrect, the end product will be inaccurate. Therefore, one of the most fundamental concepts that engineering and design students need to know is the Unit Conversion Formula. When you design a mechanical component, figure out a building dimension, build an electrical circuit, or create a CAD drawing, you can perform your task with accuracy and consistency by using the proper Unit Conversion Formula. In this blog post, we will describe unit conversion so that engineering and design students can easily understand and apply unit conversion formula.

What is a Unit Conversion Formula?

A Unit Conversion Formula is a mathematical method used to convert a value from one unit to another without changing the actual quantity.

Basic Rule:

When converting from a higher unit to a lower unit, we multiply.
When converting from a lower unit to a higher unit, we divide.

Example 1: Higher Unit to Lower Unit (Multiply)

1 meter = 100 centimeters To convert 3 meters into centimeters: 3 × 100 = 300 centimeters

Example 2: Lower Unit to Higher Unit (Divide)

1000 grams = 1 kilogram To convert 5000 grams into kilograms: 5000 ÷ 1000 = 5 kilograms

Example (Common)

1 meter = 100 centimeters

Unit Conversion Formula:

Centimeters = Meters × 100 If you have 3 meters: 3 × 100 = 300 cm The quantity remains the same, but the unit changes.

Why Unit Conversion is Important for Engineers

Different unit systems are used for different projects. For example: SI, Metric and Imperial units. Without proper unit conversion, your calculations and drawings become inaccurate.

The benefits of Unit Conversion are:

Maintain accurate calculations
Read international drawings/specifications
Avoid design/measurement errors
Accurately scale drawings
Ensure safe and precise projects

Most Common Unit Conversion Formulas

Quantity	From	To	Formula	Calculation	Result
Length	1 meter	centimeters	m × 100	1 × 100	100 cm
Length	1 inch	millimeters	in × 25.4	1 × 25.4	25.4 mm
Area	1 square meter	square feet	m² × 10.764	1 × 10.764	10.764 ft²
Volume	1 cubic meter	liters	m³ × 1000	1 × 1000	1000 L
Mass	1 kilogram	grams	kg × 1000	1 × 1000	1000 g
Force	1 Newton	kilogram-force	N × 0.102	1 × 0.102	0.102 kgf
Pressure	1 bar	Pascal	bar × 100,000	1 × 100,000	100,000 Pa
Power	1 horsepower	watts	HP × 746	1 × 746	746 W
Energy	1 kilowatt-hour	joules	kWh × 3.6 × 10⁶	1 × 3.6 × 10⁶	3,600,000 J

Unit Conversion in Mechanical Engineering

Mechanical engineers design a products using force, torque, motion and power, and therefore require accurate unit conversions during the design process.

Common Mechanical Conversions

Quantity	Unit Conversion
Force	1 N = 0.102 kgf
Torque	1 Nm = 0.737 lb-ft
Power	1 HP = 746 W
Pressure	1 bar = 100,000 Pa

Example

A motor produces 6 HP. Convert it into watts.

Unit Conversion Formula:

Watts = HP × 746

Calculation:

6 × 746 = 4476 W So, the motor produces 4476 watts.

Unit Conversion in Civil Engineering

Civil engineers use a variety of measurements. They require conversions to read engineering drawings correctly and to accurately estimate the quantity of material they will be using in construction projects.

Common Civil Conversions

Quantity	Unit Conversion
Length	1 m = 3.281 ft
Area	1 m² = 10.764 ft²
Volume	1 m³ = 35.315 ft³
Load	1 kN = 1000 N

Example

Convert 12 cubic meters of concrete into cubic feet.

Unit Conversion Formula:

ft³ = m³ × 35.315

Calculation:

12 × 35.315 = 423.78 ft³

Unit Conversion in Electrical Engineering

Electrical engineers use electrical units. Correct conversion while designing an electrical circuit and performing electrical power calculations is essential to an engineers ability to design the circuit correctly.

Common Electrical Conversions

Quantity	Unit Conversion
Power	1 kW = 1000 W
Voltage	1 kV = 1000 V
Current	1 A = 1000 mA
Energy	1 kWh = 3.6 × 10⁶ J

Example

Convert 1.8 kW into watts.

Unit Conversion Formula:

W = kW × 1000

Calculation:

1.8 × 1000 = 1800 W

Unit Conversion Formula in Design and CAD

Many designers who work with AutoCAD, SolidWorks, SketchUp, and Revit use various units when creating designs. Drawings can be presented in an inch format or they can be in millimeter or meter formats. Using the appropriate Unit Conversion Formula will assist designers in:

Correctly scaling drawings
Converting client dimensions
Maintaining the proper dimensions of the product
Working with international standards.

Common Design Conversions

Quantity	Unit Conversion
Length	1 inch = 25.4 mm
Length	1 foot = 304.8 mm
Length	1 meter = 1000 mm
Area	1 ft² = 0.093 m²

Example

A product length is 2.5 inches. Convert it into millimeters. Unit Conversion Formula: mm = inches × 25.4

Calculation:

2.5 × 25.4 = 63.5 mm So, the product length is 63.5 mm.

Step-by-Step Method to Use a Unit Conversion Formula

Identify the original unit.
Identify the required unit.
Find the correct Unit Conversion Formula.
Multiply or divide as per the formula.
Write the final value with the correct unit.

Example

Convert 90 centimeters into meters.

Unit Conversion Formula:

m = cm ÷ 100

Calculation:

90 ÷ 100 = 0.9 m

Quick Reference Conversion Table

Unit	Equivalent
1 meter	100 cm
1 kilometer	1000 m
1 kilogram	1000 g
1 kW	1000 W
1 MPa	1,000,000 Pa

Tips to Avoid Conversion Errors

Always put units in every calculation step
Convert all measurements to the same unit before you begin
Use SI units where possible
Keep a conversion chart close by
Double check the Unit Conversion Formula before your final answer

Conclusion

Unit Conversion Formula is a very basic, yet one of the essential principles that mechanical, civil, electrical, and design students encounter in their studies. Unit conversion helps maintain accurate measurements while providing proper scaling and eliminating costly mistakes in actual designs. In any everyday technical task involving conversion of power in a mechanical system, volume in a civil, voltage in an electrical circuit, or dimension in a CAD file the Unit Conversion Formula is relevant to each of these disciplines. Through familiarity with these standard formulas and the practice of easy example problems, students can feel confident using the Unit Conversion Formula as they begin their engineering or design careers.