20mcg of UK T3 is thought to be around 60 mcg (in in its 'effect'). 25mcg levo approx 75 - 100mcg levo.
This is an excerpt from a link 80 Page just for info and is taken from page 80:-
Journal of Orthomolecular Medicine Vol 28, No 2, 2013
Dose Selection in T3/T4 Study RCTs. The second logical basis for a conclusion is the actions taken, i.e., the doses given to the
subjects. Most subjects received T3 below its adult starting dose of 25 mcg/day.
The subjects in RCTs received T3 in some ratio to the withdrawn T4. The various RCTs used T4:T3 ratios of 14:1, 10:1, and 5:1. Subsequent re-
search by the US National Institutes of Health (NIH) found the therapeutic equivalence was 3:1.
Thus, most of the subjects were under treated with the T3/T4 combination. In light of the NIH finding, the conclusion that T3
therapy is never needed is invalid