Two stick counts that do not agree
Casing legs pack badly and footage arithmetic does not know it. An 80-11/16 in leg on a 16 ft stick takes a second leg and leaves 30-1/2 in, which is head stock at best and never another leg. Divide total footage by 16 and you have quietly assumed the offcuts can be welded together.
So the page prints both. The packed count lays every actual piece onto sticks, longest first. The footage count divides the ordered total, which already carries the mitre allowance and the waste percentage. They are not measuring the same thing, and neither is reliably the larger — with the schedule sitting in the form the pack comes out at 15 sticks against 16 by footage, and switching to butted heads cased both sides flips it to 26 against 25. Buy the larger of the two, which is what the page tells you to do.
What each opening actually turns into
A door cased on one side is three pieces: two legs and a head. The legs run the opening height plus the reveal at the head plus whatever you leave to trim to the floor. The head runs the opening width plus a reveal each side plus the casing width each side, because on a mitred head the outside corner of the casing is what sets the length.
A window done picture-frame is four pieces, because the bottom is another head. A window with a stool and apron is three pieces of casing and then two pieces that are not casing at all, and the page keeps those separate: the stool is thicker stock and the apron is often a different profile, so folding them into the casing stick count would give a number that buys the wrong wood.
A butted head changes the head length rather than the leg length. Instead of running to the outside corner of a mitre, it runs past the outside edge of each leg by the horn you set, and the mitre count for that opening drops to zero.
The mitre offcut, counted the pessimistic way
Cut a 45 into the end of a 2-1/4 in casing and a triangle 2-1/4 in long falls off. The page charges that for every mitred end, which is the upper bound: a careful carpenter cutting two opposing mitres out of one stick can sometimes share the cut and get half of it back. With the default schedule that allowance runs to a few feet across the house, which is the difference between finishing with short pieces spare and finishing with a phone call.
The extra waste percentage sits on top and covers the things that are not geometry — the blown cut, the knot in the wrong place, the piece that walked on the saw fence.
The reveal is a decision, made once
Three sixteenths sits in the field by default because it is a common choice, not because anything says so. An eighth reads tighter and shows every jamb that is not straight; a quarter is forgiving and reads heavier. What matters far more than the number is that it is the same at every opening in the house, because the eye compares two doorways across a hallway instantly and will not compare either of them to a drawing.
The reveal also has to have somewhere to sit, which means the jamb has to finish flush with the wall. That is the jamb width question and it gets settled before casing is ordered, not after.
Reading the format
One opening size per line: width, an x, height, optionally another x and a quantity, then a word. The word decides the shape — door, window, or window stool for a stool and apron. Lines starting with a hash are skipped, so you can leave notes in the list. Anything the parser cannot read is reported back to you rather than silently dropped.
Sizes are the opening, not the casing and not the door slab. If you are working from door sizes, the opening is what the jamb makes, which is the slab plus the gaps.
Questions people ask
How much casing does a door take?
Three pieces on one side. With the defaults — a 3/16 reveal, 2-1/4 casing and half an inch left to trim at the floor — a 36 by 80 door gives two legs at 80-11/16 in and a head at 40-7/8 in, so about 17 linear feet before waste. Case it both sides and double it.
Why is the head longer than the opening width?
Because on a mitred head the length is measured to the outside corner. The head has to cover the opening, plus a reveal at each jamb, plus the full casing width at each side so the mitre has something to meet. On a 36 in opening at 3/16 reveal and 2-1/4 casing that is 40-7/8 in. A butted head is longer still by whatever horn you leave past the legs.
How many sticks of casing for a whole house?
Two numbers, and they disagree. The page packs every actual leg and head onto sticks longest-first, and it also divides the ordered footage by the stick length. The pack knows that a 30-1/2 in leftover is never another leg; the footage figure carries the mitre and waste allowances the pack leaves out. On the schedule in the form they come out 15 against 16, and on butted heads cased both sides they come out 26 against 25. Buy the larger.
What reveal should I use on door casing?
This page states none and there is no standard. Three sixteenths is a common choice, an eighth reads tighter and less forgiving, a quarter reads heavier. The consequential part is consistency across the house rather than the number itself, since two doorways in the same sightline get compared and neither gets compared to a drawing.
Does the calculator include the stool and apron?
It reports them but keeps them out of the casing total. A stool is thicker stock than casing and an apron is frequently a different profile, so adding their footage to the stick count would produce a number that buys the wrong material. They are listed with their own cut lengths in a separate block.