The sticker count is a multiplication, not a guess
Two numbers make it. Stickers along the length is the board length divided by the spacing, plus one, because both ends get a sticker as well as everything in between: an 8 foot board at 24 inch centres takes five, not four. Layers is roughly the course count, one under each course if the bottom course is on stickers over the bearers. Thirty courses of 8 foot boards at 24 inches is 150 stickers for one pile. At 16 inch spacing the same pile takes 210.
Then there is the stock they come out of. Those 150 stickers, 3/4 by 1-1/2 by 48 inches, are 600 lineal feet and around 56 board feet of wood. Stickers are not free and they are not scrap: they get reused for years, and a shop running several piles has a real inventory of them.
What a green pile weighs
Board feet convert to cubic feet by dividing by twelve, because a board foot is 144 cubic inches and a cubic foot is 1728. Nine hundred board feet is 75 cubic feet. What that weighs depends entirely on the species and on how wet it is, and the range across species and moisture states is wide enough that a single number would be misleading, which is why the density field is yours to fill. At 45 pounds a cubic foot, 900 board feet is a little over 3,300 pounds sitting on whatever is under it.
Spread over a 4 foot by 8 foot footprint that is around 105 pounds per square foot, and shared between three bearers it is about 1,100 pounds each, assuming the ground under all three is doing its job. It usually is not, which is the thing that starts most stack failures.
Where the rest of it lives
How much water comes out of that pile as it dries, and how much narrower the boards get, is the drying water weight and shrinkage calculator. If the pile is going into a kiln rather than sitting outside, the board feet per stack from here feed straight into the kiln charge and throughput calculator. The boards themselves came from the log cut plan calculator, and once they are dry and racked indoors the loads on the rack are the lumber rack load calculator.
Sticker spacing, pile orientation, roof, and how long a given species and thickness takes to reach a given moisture content are all questions with real answers, and those answers live in drying references and extension service publications rather than in a calculator. This page will tell you what your layout produces. It will not tell you whether your layout is a good one.
Questions people ask
Why is it stickers per layer plus one?
Because the ends count. If you space stickers 24 inches apart down an 8 foot board you get spacings at 0, 24, 48, 72 and 96 inches, which is five stickers for four gaps. Forgetting the plus one is how people end up short by one sticker per layer, which on a thirty course pile is thirty stickers. The page also shows how far the board runs past the last sticker, because a spacing that does not divide the length leaves an unsupported tail at the end.
Does the bottom course need stickers under it?
The page lets you set it either way because both are done, and the difference is one sticker layer. Putting stickers under the bottom course means the bearer spacing and the sticker spacing are independent of each other; putting the boards straight on the bearers means the bearers are doing both jobs and their spacing is the only span that matters. Which is right depends on what your bearers are and how the pile is being handled.
How wet is green lumber, in weight terms?
Wetter than the wood, often much wetter. In green wood the water can outweigh the dry wood substance, which is why a fresh pile can be most of a ton heavier than the same pile a year later. The exact figure depends on species and on where in the tree it came from, and it is not something a calculator can supply for you. Weigh a board of known volume if you want a number for your own wood, or take a green density figure from a species reference.
What spacing should I use for the stickers?
That is a question for a drying reference or an extension publication for your species and thickness, not for this page. The variables are the species, the thickness, how prone the wood is to distorting and how fast it is drying, and the published guidance exists precisely because the answer is not obvious. What this page does is turn whatever spacing you choose into a sticker count, a length of sticker stock to cut and an unsupported end length, so you can see the consequence of the choice.
Can I just work out the board feet from the pile size?
Only roughly, and the gap is the air. A pile 48 inches wide with 8 inch boards and 3/4 inch gaps holds five boards per course, which is 40 inches of wood and 8 inches of nothing, so the outside dimensions overstate the wood by a fifth before you count the sticker thickness in the height. This page counts the boards rather than the box, which is why the board width and gap are separate fields.