Well, if you're going to measure it to apply standard herbalism formulae, you really must have some form of measuring device, preferably one that reads in grams, with reasonable accuracy. (If you have ounces, you can come quite close by figuring 28 grams per ounce.) Then you'd want to shoot for something like a 1:5 herb-to-menstruum strength for dried herb (for example, 100 grams of herb to 500 milliliters of menstruum). If using fresh herb, 1:2 is a better herb strength, since the fresh herb contributes a substantial amount of water to the slurry.

On the other hand, it's not strictly necessary to use a standard formula; after all, there's no such thing as a standard human!

Beginning manuals will often tell you that traditionally, medicine makers started with jar that's large enough to hold your amount of herb, plus perhaps 20% of air space above it. Then you add your menstruum (I used 75% alcohol/water for dried Hypericum perforatum, myself; would use 95% alcohol for fresh herb) until there's enough to cover the herb, with perhaps another quarter-inch of liquid above the herb, and enough air space above that to allow for proper succussion.

Once the herb is macerated and strained, just take it slowly with regard to dosage. Start with a smaller amount (like 10 drops, three times a day for an adult?), and once you're satisfied that you tolerate it well, increase it gradually until you're at a whole dose (perhaps 30-50 drops). Because of variations in the plants between suppliers, seasons and growing locale, of course, it's wise to approach it gradually, and remember that the next batch will likely be at least a somewhat different strength. You might do well to back off a bit on dosage of the new batch, and again increase it gradually until the effect is where you want it to be.

Happy tincturing!

-BH

Just because I've found it useful, http://www.onlineconversion.com/ this site has almost any conversion you need to know! :o) I've used it for translating European cooking recipes.