Engineering Reference

Unit Converter

Convert between the units engineers actually use — length, pressure, force, torque and temperature — with the exact factors.

Page last changed 2026-10-19 · based on n/a — standard engineering relationships, no single governing revision

Quick Answer

Enter a value in any field and the others update. Length uses 25.4 mm per inch exactly; pressure uses 1 psi = 6.894757 kPa; temperature is the only one that needs an offset, not just a factor.

Unit Converter

The Formulas Used

Length 1 in = 25.4 mm (exact) · Pressure 1 psi = 6.894757 kPa
Torque 1 lb·ft = 1.355818 N·m · Force 1 lbf = 4.448222 N
Temperature is the exception: °F = °C × 9/5 + 32 — an offset as well as a factor.

Temperature Is Different

Every other conversion on this page is a pure multiplication, because the units share a zero point. Temperature scales do not — 0 °C and 0 °F are different temperatures — so a conversion needs both a factor and an offset.

This matters when converting temperature differences: a change of 1 °C equals a change of 1.8 °F, with no offset. Mixing the two up is a common source of error in thermal expansion and heat transfer work.

Where the Factors Come From

The length and mass conversions are exact by definition — the inch has been defined as exactly 25.4 mm since 1959. Pressure and torque conversions are derived from those plus the standard gravity definition, so they carry more decimal places than are usually needed.

Frequently Asked Questions

How many mm in an inch?
Exactly 25.4. The inch has been defined as 25.4 mm since 1959, so the conversion is exact and not subject to rounding.
How do I convert psi to bar?
Multiply by 0.068948, or divide by 14.50377. 100 psi is 6.895 bar, and 1 bar is 14.504 psi.
How do I convert Nm to lb-ft?
Multiply by 0.737562. 10 N·m is 7.376 lb·ft, and 1 lb·ft is 1.356 N·m — the two units differ by about 36%.
Why is temperature conversion different?
Because the scales have different zero points. Converting between °C and °F needs an offset as well as a factor, unlike length or pressure where both scales share a zero.
How do I convert a temperature difference?
Multiply by 1.8 only — no offset. A rise of 10 °C is a rise of 18 °F. Adding the 32 is the common mistake here.

Related

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

#SourceTypeRevision / method
[1]Values computed in your browserderivedEvaluated locally from the formulas shown on the page. No data leaves the device.

Data Sources

StandardRevisionWhat it covers on this page
Formulas as shown on this pagen/a — standard engineering relationships, no single governing revisionevery value this calculator produces

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

Derived values — the following values on this page are calculated, not taken directly from the standard:

ValueHow it is derived
All outputsComputed in the browser from the formulas above. No data leaves the device.

Outputs are computed from the formulas shown. Verify against the governing standard for design or acceptance work.

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