Numerical value of physical constants Mathematica 10

In physics, the Planck constant may be used as a natural unit.

If you want to switch to another unit system, use UnitConvert[].

For example, you can switch to standard SI units this way:

UnitConvert[Quantity[1, "PlanckConstant"], "SIBase"]

which will give you:

Quantity[6.626070*10^-34, ("Kilograms" ("Meters")^2)/("Seconds")]

This can be done at the end of calculation.

If you like to get rid of Quantity head, just do:

QuantityMagnitude[%]

which outputs:

6.626070*10^-34