Engineering Unit Converter (Metric, US and UK Imperial)

Convert engineering quantities between metric, US and UK imperial units.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Engineering data comes in mixed units, and the same word can mean different things. A ton is 1000 kg (metric tonne), 2000 lb (US short ton, 907.18 kg) or 2240 lb (UK long ton, 1016.05 kg). A US gallon is 3.785 litres and a UK gallon is 4.546 litres.

This converter keeps those apart. Pick the unit you have and the unit you want from the same group. Temperatures are converted through kelvin. Factors are exact definitions where they exist.

Formulas used

  • 1\ \text{in} = 25.4\ \text{mm}
  • 1\ \text{lb} = 0.45359237\ \text{kg}
  • 1\ \text{psi} = 6.894757\ \text{kPa}

Worked example

With the default numbers in the calculator above:

  1. Conversion factor: 1 psi = 6.8947573 kPa
  2. Converted value: 6.8948 kPa
  3. And back again (check): 1 psi

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

What is the difference between a US and UK ton?

The US short ton is 2000 lb. The UK long ton is 2240 lb. The metric tonne is 1000 kg.

Why do US and UK gallons per minute differ?

Because the gallons differ: 3.785 and 4.546 litres.

How do I convert a temperature difference?

By the scale factor only: 1 K = 1 degree Celsius = 1.8 degrees Fahrenheit.

Related calculators

Further reading: NIST Guide for the Use of the International System of Units (SI).

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