Stairs/Ladder?

I know there is a forumula for figuring out stairs and maybe my stairs are classifed as a ladder due to the angle? I didn't want to make things to complicated so here is how I went about designing my stairs/ladder.

Using 1 - 10 ft. 2 x 8 pressure treated board, I leaned it up from the ground to the entry way in the trap door opening. I first scribed a line on the foot end of the board and cut an angle to make it level with the ground. I then did the same at the top making the cut horizontal to the upright floor joist. I repeated this on a 2nd 10 ft. 2 x 8 so now I have 2 stringers with the angles cut on both ends. With 1 of the stringers in the upright position, I measured to what I considered would be a comfortable step at that angle. I determined that a 1 foot rise would work which was excellent because I was dealing with a 10 ft. board (I like square numbers). I would need to router out 8 tread slots at a 1 ft spacing. With the first stringer in place, I used a level and marked each 1 foot tread position with a level horizontal line. I then routed out the tread postion at about a 3/4 inch depth. I mirrored these marks to the 2nd stringer and repeated.

I now have two stringers that I joined together with 18" treads. I used shorts from the leftover floor decking (Katie did all this measuring). When the stairs/ladder was complete, I screwed on a piece of plywood to the end that would join the floor joists. I then hoisted the stairs to the opening and screwed the plywood into the floor joist. It was necessary to level the ground with a shovel to make everything fit perfect.