My Basic Soils
5 parts pine bark fines (partially composted fines are best)
1 part sphagnum peat (not reed or sedge peat please)
1-2 parts perlite
garden lime (or gypsum in some cases)
controlled release fertilizer (if preferred)
micro-nutrient powder, other continued source of micro-nutrients, or fertilizer
with all nutrients - including minors

Big batch:
2-3 cu ft pine bark fines
5 gallons peat
5 gallons perlite
2 cups dolomitic (garden) lime (or gypsum in some cases)
2 cups CRF (if preferred)
1/2 cup micro-nutrient powder (or other source of the minors - provided in some
fertilizers)

Small batch:
3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
4 tbsp lime (or gypsum in some cases)
1/4 cup CRF (if preferred)
micro-nutrient powder (or other source of the minors)

For long term (especially woody) plantings and houseplants, I use a superb
soil that is extremely durable and structurally sound. The basic mix is equal
parts of pine bark, Turface, and crushed granite.

1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface or Diatonacious Earth
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil
CRF (if desired)
Source of micro-nutrients or use a fertilizer that contains all essentials I
use 1/8 -1/4 tsp Epsom salts per gallon of fertilizer solution when I fertilize
(check your fertilizer - if it is soluble, it is probable it does not contain
Ca or Mg.

I know 'Gritty Mix" has equal parts of pine bark, Turface, and crushed granite.

I need 40 cu. ft. of gritty mix.

How many bags of each ingredient should I buy? (I don't want to have to go back and buy more).

You'll have to find out how many cubic ft is in each bag and do the math.

Each bag of the NAPA contains 24 quarts (wet or dry?) How many cu. ft. is that?

Each bag of the Gran-I-Grit and the Cherry Stone weights 50 lbs? How many cu. ft. is that?

Gary, google is your friend. type "convert 24 quarts to cubic feet"

It ends up being like .8cuft.

24US qt liquid= 0.802 ft³

24US qt dry= 0.933 ft³

Oh I'm sorry I made a mistake. It is dry quarts. So, .9cuft.