Engineering Unit Converter
Convert any engineering unit (by discipline for structural and steel, HVAC, electrical, plumbing, architecture, LEED and geotechnics, or any unit to any unit) with every factor taken from NIST SP 811 and shown with its source.
Every factor is built from the exact definitions, the SI prefixes, the 1959 foot (0.3048 m) and pound (0.453 592 37 kg), standard gravity g_n = 9.806 65 m/s², 231 in³ to the U.S. gallon, the IT Btu and the ton of refrigeration (12 000 Btu/h), and matched to the value NIST SP 811 Appendix B.8 prints; the measured units carry NIST's seven digits. Pick a discipline for the quantities its engineers convert every week, or search any unit by symbol or name, in English or Arabic. Temperature and temperature difference are separate quantities, gauge and absolute pressure are named on the quantity, and the conversions that are not one factor (AWG, feet-inches-fractions, slopes, degrees-minutes-seconds, COP, EER and kW per ton) run on their own equations.
By symbol or by name, in English or Arabic. Press / to search from anywhere on the page, ↑ ↓ and Enter to pick.
Display options
Very large and very small values are written in engineering notation (an exponent that is a multiple of 3).
In every unit
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Where the factors come from
The exact factors are exact; the rest carry the digits NIST prints. Every result shows its factor and its source beneath it.
Questions engineers ask
Where do the conversion factors come from?
From NIST Special Publication 811 (2008), Appendix B.8, for every non-SI unit, and from the SI Brochure for the SI prefixes and the units accepted with the SI. Where a unit is defined exactly (the foot as 0.3048 m, the pound as 0.453 592 37 kg, the pound-force at g_n = 9.806 65 m/s², the U.S. gallon as 231 in³, the IT Btu, the ton of refrigeration as 12 000 Btu/h) the converter uses the exact definition and shows the value NIST prints beside it. Every result shows its factor, whether it is exact, and its source.
Why is 10 °C sometimes 50 °F and sometimes 18 °F?
A temperature is a reading on a scale with its own zero: 10 °C is 50 °F. A temperature difference is an interval: a rise of 10 °C is a rise of 18 °F. The converter keeps them as two quantities, and from either one you can switch to the other with the same value.
How are gauge and absolute pressure handled?
Choose the reference of the value you enter and of the answer you want. Absolute pressure is gauge pressure plus the atmospheric pressure, which is the standard atmosphere, 101.325 kPa, unless you enter the local value. The reference is named on the quantity, as NIST SP 811 asks, rather than written into the unit as psig or bara. A duct or fan pressure is a difference and has no reference.
How is an AWG size converted to mm²?
By the ASTM B258 definition: the diameter of gauge n is 0.005 in × 92^((36 − n)/39), with 1/0 to 4/0 as n = 0 to −3; the nominal diameter is rounded to 0.1 mil and the area in circular mils is its square. The page gives the nearest IEC 60228 size and the next larger one; an equal area is not an equal current rating.
Can it convert kW to kVA?
Only through the power factor of the load: the active power in kW is the apparent power in kVA times the power factor (IEC 60050, IEV 131-11-46). That is not a unit conversion, so the page asks for the power factor and says so.
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