Link	Website	PyPI DLs/month	GitHub Stars	Used by	Built-in units	Built-in constants	Arbitrary prefixes	np scalar array	np object array	Decimal	Fraction	Uncertainties	string	absolute °C	dB	Syntax	Comments
scipy.constants	scipy.org/...	167,385	7,087	181,360	Yes 50	Yes 400 in CODATA	No	- no unit objects	- no unit objects	- no unit objects	- no unit objects	- no unit objects	- no unit objects	No	No	constants.c == 299792458.0	Just tables of numerical constants; unit-aware calculations not supported. scipy.constants.physical_constants specifies units as strings and uncertainties. Could be used to supply other packages with coefficients.
sympy.physics.units	sympy.org/...	55,424	6,924	18,324	Yes 200?	Yes	- u.mega*u.meter but not u.megameter	No	Yes array([1, 2, 3])*u.m	- converts to sympy	- converts to sympy					cm = u.m/100
astropy.units	astropy.org/...	11,358	2,435	13,777	Yes	Yes	No	Yes	-					Yes	Yes	15.1 * u.meter / (32.0 * u.second)
Pint	github.com/...	35,746	1,128	1,579	Yes	Yes	Yes Mm, GV, etc.	Yes array([1,2,3])*ureg.m or ureg.m*array([1,2,3])	No ValueError	Yes	Yes	Yes built-in	Yes	Yes	No	V = 1*ureg.dm**3
unyt	readthedocs.io/...		243	29	Yes 101	Yes 33	Yes km									4*m + 3*cm - 5*ft + 6*yard
Quantities	readthedocs.org	3,917	147	231				Yes array([1,2,3]) * pq.J						No
Units	bitbucket.org/...	1,376
numericalunits	python.org/...	445	69														Overflow issues, random set of units = not deterministic, need to do calculations twice to confirm they are being done correctly
SciMath Units	readthedocs.org/...	430	36									Yes built-in
Buckingham	github.com/...	361	20	0	Yes 53	No	Yes									V = Number(1,dims='decimeter^3')	Single file
Unum	bitbucket.org/...	334
natu	github.io/...	315			Yes	Yes 40	Yes	Yes m*array([1, 2, 3])	Yes array([1, 2, 3])*m	No	No	Yes	No	Yes	Yes	V = 1*dm**3	weird format for dB, Hz != 1/s, "pre-release state"
misu	github.com/...	308	11	0
Magnitude	juanreyero.com/...	238	16	31	Yes	Yes	Yes
udunitspy	github.com/...	188	2	0													Python wrapper for UDUNITS2
scinumtools.units	github.com/...	471	5		Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes K, Cel, degF, degR	Yes dB, Np, dBm, dBmW, ... (both B and dB)	quant(3, 'J').to('kg*m2/s2') quant([5.9e-4, 5.2e+5], 'J*s-1').to('W') 33*unit('kg'), const('c') 3*unit.m/unit.s	No registries needed like for Pint. Documentation is available here: github.io/...
DimPy	cam.ac.uk/...	0
Scalar	russp.us/...	0
ScientificPython PhysicalQuantities	cnrs-orleans.fr/...	0