Hi:

I just want to confirm that nmol/L to ng/L is 3.14

So if its 5.3nmol/L that would be 1.67ng/L , correct?

TIA!!

No, 3.14 is not correct. The conversion is specific for each test as it works with the substance and its molecular mass so:
Progesterone ng/mL 3.18 nmol/L
which is taken from this website http://jama.ama-assn.org/misc/auinst_si.dtl
For seat of the pants round number calculations you can use 3 and say that 15nmol/L = 5ng/mL

Thank you!