Jim is right on dividing total height by the number of risers and keep them all the same. If the total length is too long then you can put in a landing and start the remainder of the stairs down in another direction. Some house plans don't allow for much room length ways hence the landing.
My review of the UBC and CABO codes (they differ a little) show a minimum tread depth of 9" and a max riser height of 8". Minimum headroom is 6'8" above the nosing line.
There are different general rules but figure riser height of 6" to 8" and tread depth of 9" to 12". 7" high and 10" to 11 1/2" deep is common. One general rule said to add them and it should be between 17 to 19.
All that said, my size 8 1/2 shoe is 11 1/2" long. A 12" nominal wide board measures 11 1/2" and that makes a nice tread to step on with the full weight of your body. Too short and your full heel doesn't set down on the tread.
Last fall, I designed a set of stairs and figured on 7 1/8" risers and 10" treads. When reminded that a short elderly lady would be using the stairs, I bought new stringer lumber and made them with a 6" rise and 11 1/2" treads. They ended up being the nicest steps for her and me as well to walk up and down on. The entire length was longer though.
I'm not sure how you are in the middle of building a house and don't have any architecural drawings for the stairs? A lot of design goes into where stairs fit in the upstairs and downstairs floorplans. At any rate, good luck. Also what is wrong with the treated precut stringers?