Engineering Unit Converter with Unit Expressions (psi, MPa, N·m, lbf·ft…)
Convert any engineering unit or compound expression (lbf*ft to N*m, psi to MPa, kg*m/s^2 to N) with dimension checking · free, no signup
See Engineering Unit Converter with Unit Expressions (psi, MPa, N·m, lbf·ft…) in action
Free Engineering Unit Converter with Dimensional Analysis
Most unit converters only handle a fixed list of single units, which is no help when your quantity is lbf·ft, kgf/cm², BTU/h or kg·m²/s². This converter understands unit expressions: type any combination of units with multiplication (a star or a space), division, exponents and parentheses — for example lbf*ft, N/mm^2, W/(m*K), ft^3/min or m/s^2 — and convert it to any other expression of the same dimension. SI prefixes (µ, m, k, M, G…) work on SI units, so kPa, MPa, GPa, mm, µm, kN, kW and MJ are all recognised, along with the imperial and US customary units engineers use (in, ft, lb, lbf, kip, psi, ksi, hp, BTU, gal, cfm and many more).
Every conversion is checked by dimensional analysis: the tool computes the SI dimension of each side and refuses to convert incompatible quantities such as metres to seconds, naming the dimension of each. It also tells you what kind of quantity you are converting (force, pressure/stress, energy/torque, power, flow and so on) and the exact factor, using the NIST conversion constants — 1 psi = 6894.757293168 Pa, 1 lbf = 4.4482216152605 N, 1 hp = 745.69987158227 W. Temperatures (°C, °F, K) are handled on their own scale.
Key features
Compound unit expressions
Multiply, divide, exponents and parentheses — lbf*ft, W/(m*K), ft^3/min.
Dimension checking
Refuses incompatible conversions and shows the SI dimension.
SI prefixes
µ, m, k, M, G… on SI units: MPa, kN, µm, GW.
NIST constants
Exact standard factors with the factor shown.
How to use it
- Enter a value and the unit expression to convert from.
- Enter the unit expression to convert to.
- Read the result, the factor and the quantity type.
- Use the swap button or the common-conversion chips.
Worked example
Example
1,000 lbf·ft converts to 1,355.82 N·m; 3,000 psi is 20.684 MPa; 60 mph is 26.8224 m/s; trying to convert metres to seconds returns an 'incompatible units' message instead of a wrong number.
Who uses this tool
Engineers and students
Convert mixed US and SI units safely.
Machinists and fitters
Torque, pressure and speed conversions.
Scientists
Check that an equation's units balance.
Tips for the best results
- Use lbf for force and lb for mass.
- Write exponents with ^ (m^2) or a digit (m2, ft3).
- Use parentheses for denominators with several units: W/(m*K).
- Check the quantity name to make sure it is what you intended.
Common mistakes to avoid
- Confusing lb (mass) with lbf (force).
- Mixing N·m torque with J energy — same dimension, different meaning.
- Typing a space-separated unit when you meant a ratio.
Why use AZRS QuickFix?
It is 100% free, needs no signup and has no watermark or usage limits. The tool runs in your browser, so what you type stays on your device, and it works on phones, tablets and desktops. New tools are added every week — bookmark this page or browse the full QuickFix toolbox.
Frequently asked questions
Which units are supported?
Metric and US customary units for length, mass, time, force, pressure, energy, power, volume, flow, electrical and more — see the list on the page.
Can it convert temperature?
Yes, °C, °F and K on a single unit.
Why did it refuse my conversion?
The two sides have different dimensions, so no factor exists.
Is it free?
Yes.