I may have used a slightly different target percent of range as you did, but yes, you did your math perfectly.
The formula I use to find a target level is:
Top of range minus bottom of range = A
by the desired percentage of range = B
to the bottom number in the range. Result will be your target level.
Let's calculate your FT4 target for an example. I'll use 70% as the target.
Free T4 Range 9.0-23.0
23.0 - 9.0 = 14.0. (A
) 14.0 X .70 = 2.87 (B
) 2.87 + 3.50 = 6.37