I learned some Tincture lore yesterday that seems relevant for this discussion.
The strength of a cannabis tincture is often measured on the "Whole Plant Scale," which is a ratio of the amount of herb in grams divided by the volume of alcohol in ounces. Tincture recipes commonly shoot for a potency of around 3.5gr / ounce and assume a normal dose will be between one half to one ml.
So, in my recent batch I used one oz of bud in two cups of Everclear producing a "Whole Plant" potency of 1.86 (29.7g / 16oz). I found that rather weak and reduced the tincture liquid volume by half. That doubled the potency to around 3.7 (1.86 x 2). My bedtime does of 1 - 2 ml seems perfect for a great night's sleep.
Also, the Magic Butter recipe calls for 54gr (2oz) of weed and 16 oz of Everclear, producing a potency of 54 / 16 = 3.7! Voila!
To round this out, another method used to estimate tincture potency uses the following formula:
(THC content in % x Amount of Herb in mg x Extraction efficiency in % ) / Alcohol in ml = the mg/ml of THC in your tincture.
So, let’s assume that the THC content of our herb is 20%. The Magic Butter recipe max dose calls for 2oz (59 grams or 59000 mg) of herb in 16oz (454ml) of alcohol. A tincture extracts about 75% of the available THC. So, the math looks like this:
(0.2 x 59,000 mg x 0.75) / 454 ml = 19.5 mg/ml. --A quite potent concoction.
(Hat tip to @ReikoX for the formulas!)