Editing GNU Units (section)

== Examples ==
The examples that follow show results from GNU ''units'' version 2.10.

=== Interactive mode ===
<!-- GNU units version 2.10, Windows XP SP3 -->
<pre>
Currency exchange rates from www.timegenie.com on 2014-03-28
2729 units, 92 prefixes, 77 nonlinear units

You have: 10 furlongs
You want: miles
        * 1.25
        / 0.8
You have: 1 gallon + 3 pints
You want: quarts
        * 5.5
        / 0.18181818
You have: sqrt(meter)
                    ^
Unit not a root
You have: sqrt(acre)
You want: ft
        * 208.71033
        / 0.0047913298
You have: 21 btu + 6500 ft lbf
You want: btu
        * 29.352939
        / 0.034068139
You have: _
You want: J
        * 30968.99
        / 3.2290366e-005
You have: 3.277 hr
You want: time
        3 hr + 16 min + 37.2 sec
You have: 1|2 inch
You want: cm
        * 1.27
        / 0.78740157
</pre>

The underscore ('_') is used to indicate the result of the last successful unit conversion.

=== On the command line (non-interactive) ===
<!-- GNU units version 2.10, Windows XP SP3, cmd.exe -->
<syntaxhighlight lang="doscon">
C:\>units "ten furlongs per fortnight" "kilometers per hour"
        * 0.0059871429
        / 167.02458
</syntaxhighlight>
<!-- GNU units version 2.10, Windows XP SP3, PTC MKS C shell -->
<syntaxhighlight lang="console">
% units cup ounces
conformability error
        0.00023658824 m^3
        0.028349523 kg
</syntaxhighlight>

=== Complex units expressions ===
One form of the [[Darcy–Weisbach equation]] for [[fluid flow]] is
: <math>\Delta P = \frac {8} {\pi^2} \rho fL \frac {Q^2} {d^5} \,,</math>
where Δ''P'' is the pressure drop, ''ρ'' is the mass density, ''f'' is the (dimensionless) friction factor, ''L'' is the length of the pipe, ''Q'' is the volumetric flow rate, and ''d'' is the pipe diameter. It might be desirable to have the equation in the form
: <math>\Delta P = A_1 \,\rho fL \frac {Q^2} {d^5}</math>
that would accept typical US units; the constant ''A''<sub>1</sub> could be determined manually using the [[Units conversion by factor-label|unit-factor method]], but it could be determined more quickly and easily using ''units'':<ref>GNU units version 2.10, Windows XP SP3, PTC MKS Korn shell</ref>
<syntaxhighlight lang="console">
$ units "(8/pi^2)(lbm/ft^3)ft(ft^3/s)^2(1/in^5)" psi
        * 43.533969
        / 0.022970568
</syntaxhighlight>
Crane Technical Paper No. 410,<ref>
{{Cite book|title=''Technical Paper No. 410,'' Flow of Fluids through Valves, Fittings, and Pipe|publisher=Crane Co|location=New York|year=1985|url=http://www.flowoffluids.com/publications/crane-tp-410.aspx}}
</ref>
Eq.&nbsp;3-5, gives the multiplicative value as 43.5.