Hi, I am writing on behalf of a friend and we are trying to work out the above ratio. The numbers are: free T3=3.1 pmol/L and her reverse T3 is 0.40ng/mL. We have tried converting them to the same units, using the ratio calculator on stopthe thyroidmadness.com and many others and each time we get a different answer. I cannot find an authoritative source on how best to do this conversion. Converting to the same units of measurement, using different ones which some ratio calculators seem to allow... any help would be most appreciated.