No scientist here but i'd use about a teaspoon per gallon of soil in start-up soil mix.
About one part peirlite to one part soil since your not using potting soil maybe a bit more (in the big city we use units of mesurment like cubic foot or yard) What is a "normal" bag? the one in my tiny back yard is 3.5 cubic feet.
This soil mix will be a little high maintainace as far as watering but with all that peirlite root rot is almost unheard of.
Wisdom of the new ancients half inch of peirlit in bottom of pot for happy plant.
With this soil mix it will be nessassary to add more lime as the plant and soil grow, I add a pinch (NO MORE THAN A PNCH!) almost every time I water. When I water I also, every time (except when I shot for the stars with the liquid nutrients and have to flush with extree water) feed with a liquid all around fertilizer and a dolop of soaked solids: bat guano (high-n for veg. high-p for flower), quality mulch, Whitny Farms Mix (or sutable Organic mix with soil fugus and mycilin {the city I live in: I'm the worst speller by far} and of course just a pinch (like copenhagen for a two-year-old) of lime.
NO LIME LAST SIX TO FIVE WEEKS OF FLOWERING (My rules for my grow, I've been adding a bit of lime every few days for the plants whole life, time to let the acids do what they may) NO SOLIDS LAST FIVE TO SIX WEEKS (give those chuncks of poo and animal bone a chance to decompose) LAST TWO WEEKS FLUSH.
Thank you for letting me share, sorry for the ramble.