The converter
Runs in your browser. Length, pressure, torque, mass, volume, force and temperature.
Where the factors come from
Exact by definition. The inch is 25.4 mm and the pound 0.45359237 kg (international agreement of 1959). The US gallon is 231 in³, so 3.785411784 L. The pound-force is one pound under standard gravity, 9.80665 m/s², so 4.4482216152605 N.
Derived. 1 lb-in = 4.44822 N × 0.0254 m = 0.112985 N·m; 1 lb-ft = 1.355818 N·m; 1 psi = 6.894757 kPa.
Conventional. The inch of mercury is the column at 0 °C: 3.38638 kPa, the value NIST SP 811 lists and altimeters use. Sea-level standard pressure is 29.92 inHg = 101.325 kPa.
Worked example
A torque of 135 lb-in, from AC 43.13-1B's own adapter example, on a wrench marked in N·m.
- 1 lb-in = 0.45359237 × 9.80665 × 0.0254 = 0.112985 N·m.
- 135 × 0.112985 = 15.25 N·m.
Set 15.3 N·m, then apply the adapter correction if there is one.
Limits — when NOT to use this
- Gauge and absolute pressure convert the same way, but they are not the same thing. Keep track of which one the figure is.
- US and imperial gallons differ (3.785 against 4.546 L). This converter uses US units throughout.
- Rounding. Results are shown to a sensible number of digits. Use the manufacturer's metric figure where one is published, not a conversion of the inch one.
Questions people actually ask
Is a mil a millimetre?
No. A mil is a thousandth of an inch, 0.0254 mm. Paint and sealant thicknesses are often in mils.
Why is my 20 °C difference 36 °F and not 68 °F?
A difference has no offset: 1 °C of change is 1.8 °F. The 32 °F offset applies only to a temperature reading.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B — conversion factors for inch, foot, pound, US gallon, pound-force, psi, inch of mercury (32 °F) and kilogram-force.