.. _convert: Command-line script =================== The script `pint-convert` allows a quick conversion to a target system or between arbitrary compatible units. By default, `pint-convert` converts to SI units:: $ pint-convert 225lb 225 pound = 102.05828325 kg use the `--sys` argument to change it:: $ pint-convert --sys US 102kg 102 kilogram = 224.871507429 lb or specify directly the target units:: $ pint-convert 102kg lb 102 kilogram = 224.871507429 lb The input quantity can contain expressions:: $ pint-convert 7ft+2in 7.166666666666667 foot = 2.1844 m in some cases parentheses and quotes may be needed:: $ pint-convert "225lb/(7ft+2in)" 31.3953488372093 pound / foot = 46.7214261353 kg/m If a number is omitted, 1 is assumed:: $ pint-convert km mi 1 kilometer = 0.621371192237 mi The default precision is 12 significant figures, it can be changed with `-p`, but note that the accuracy may be affected by floating-point errors:: $ pint-convert -p 3 mi 1 mile = 1.61e+03 m $ pint-convert -p 30 ly km 1 light_year = 9460730472580.80078125 km Some contexts are automatically enabled, allowing conversion between not fully compatible units:: $ pint-convert 540nm 540 nanometer = 5.4e-07 m $ pint-convert kcal/mol $ 1.0 kilocalorie / mole = 4184 kg·m²/mol/s² $ pint-convert 540nm kcal/mol 540 nanometer = 52.9471025594 kcal/mol With the `uncertainties` package, the experimental uncertainty in the physical constants is considered, and the result is given in compact notation, with the uncertainty in the last figures in parentheses:: $ pint-convert Eh eV 1 hartree = 27.21138624599(5) eV The precision is limited by both the maximum number of significant digits (`-p`) and the maximum number of uncertainty digits (`-u`, 2 by default):: $ pint-convert -p 20 Eh eV 1 hartree = 27.211386245988(52) eV $ pint-convert -p 20 -u 4 Eh eV 1 hartree = 27.21138624598847(5207) eV The uncertainty can be disabled with `-U`):: $ pint-convert -p 20 -U Eh eV 1 hartree = 27.211386245988471444 eV Correlations between experimental constants are also known, and taken into account. Use `-C` to disable it:: $ pint-convert --sys atomic m_p 1 proton_mass = 1836.15267344(11) m_e $ pint-convert --sys atomic -C m_p 1 proton_mass = 1836.15267344(79) m_e Again, note that results may differ slightly, usually in the last figure, from more authoritative sources, mainly due to floating-point errors.