Mechanical Unit Converter
Convert common mechanical engineering units
Fast reference conversions for drawing reviews, supplier notes, test data, thermal estimates, and engineering redlines.
Live converter
Unit conversions for mechanical engineering work
Pick a category, enter a value, choose source and target units, then copy the result into a review note, spreadsheet, ticket, or PDF redline.
Convert drawing dimensions, hole spacing, stock size, and inspection measurements.
Common conversions
Equivalent values
25.4 mm converted across length units.
| Unit | Symbol | Value |
|---|---|---|
| millimeter | mm | 25.4 |
| centimeter | cm | 2.54 |
| meter | m | 0.0254 |
| inch | in | 1 |
| foot | ft | 0.0833333333 |
| thousandth of an inch | mil | 1,000 |
| micrometer | um | 25,400 |
Common uses
Built for everyday mechanical conversion checks
This tool is intentionally scoped to conversions that come up during practical mechanical engineering work, not every possible unit in a physics handbook.
- Convert metric drawing dimensions to inch-based supplier notes.
- Convert lbf test readings to N or kgf for mechanical review comments.
- Convert GPa, MPa, ksi, and psi for material specifications and analysis checks.
- Convert deg C and deg F for lab, heat treat, environmental, and test requirements.
- Convert W, kW, hp, BTU/hr, BTU/min, and tons of refrigeration for thermal and power work.
- Convert N*m, lbf*in, lbf*ft, N*mm, and kgf*cm for torque callouts.
Reference formulas
Core conversion references used by the tool
The converter uses exact SI relationships where defined and standard engineering constants for common force, pressure, power, and torque conversions.
| Category | Reference | Notes |
|---|---|---|
| Length | 1 in = 25.4 mm | Use for drawing dimensions, hole spacing, stock size, and inspection measurements. |
| Force | 1 lbf = 4.4482216152605 N | Use kgf for kilogram-force. Do not treat kg mass and kgf as the same physical quantity. |
| Mass | 1 lbm = 0.45359237 kg | Use for part mass, shipping weight, samples, and material quantities. |
| Stress and pressure | 1 ksi = 6.894757293168 MPa | Useful for tensile strength, yield strength, pressure, modulus references, and hydraulic values. |
| Temperature | deg F = deg C x 9/5 + 32 | Use for lab readings, environmental specs, heat treat references, and test conditions. |
| Power | 1 W = 3.412141633 BTU/hr | The converter treats BTU/hr as a power unit, not a standalone energy quantity. |
| Torque | 1 N*m = 8.850745767 lbf*in | Use for fastener torque, motor torque, shaft torque, and fixture loading. |
Engineering caution
Keep force, mass, power, and energy separate
The converter separates force from mass because lbf and kg are not interchangeable. If your source is a load, use lbf, N, kN, kgf, or ozf. If your source is a part mass, use kg, g, lbm, oz, or tonne.
The same distinction matters for power and energy. Watts convert to BTU/hr because both are rates of energy transfer. A standalone BTU is energy, so it belongs in a different calculator.
FAQ
Mechanical unit converter questions
Can this converter handle mm to inches?
Yes. Select Length, enter the millimeter value, choose millimeter as the source unit, and choose inch as the target unit. The converter uses the exact relationship 1 inch = 25.4 millimeters.
How should I convert lbf to kg?
If the value is a force, convert lbf to kgf, not kg mass. The converter includes pound-force, newton, kilonewton, kilogram-force, and ounce-force under Force/load. Use the separate Mass category for kg, g, lbm, and oz mass.
Does W to BTU mean BTU or BTU/hr?
Watts are a unit of power, so this converter uses BTU/hr and BTU/min for compatible power conversions. A standalone BTU is an energy unit, not a power unit.
Can I use this for released engineering calculations?
Use it as a reference converter and always verify critical released values against your project requirements, controlled standards, and company calculation process.