Dito on Midwest's advice.
50-80% is optimal given the range of your lab.
The simplest calculation for this is:
(Your T4 value - T4 lower limit)/(T4 upper limit - T4 lower limit)*100 = % concentration.
You can swap out the T4 for a T3 to get your T3 values.
At 40% I was having symptoms at 5% I was unable to function. My mother and her four sisters optimize out in the TSH .8-1.1 range and FT3 and FT4 values around 70% given a 5% deviation. For instance Aunt B has Ft4 68% and FT3 and 72%, Mom FT4 73% and FT3 68%. Me still trying to get back into the 50-80% range.
I will let you know where i level out at.
Each person is different. You need to look at your FT3 and FT4 levels, make sure they are near parallel in range, in the optimal zone, where you cease to have symptoms. Ugh! A lot to worry about. Make sure your MD treats by FT3 and Ft4 values is willing to supplement T3 is needed and listens to your symptom log seriously.