Each generator on this site drafts one piece and knows nothing about the others. That is fine for a pocket on its own, and it is the whole difficulty of a garment: a pair of trousers takes six pieces, and several numbers have to travel from one draft to the next. You are the one who carries them.
This page is the part no single generator can give you. It says which to run first, exactly which value to read off one and type into another, how much fabric the whole pair needs, and the order to sew it in — which is not the order you draft it in.
One of these is automated once the waistband has been saved in the same browser session, and only if nothing else is saved in between — the session holds one source at a time, and a cleared source leaves the receiving field on its own default rather than empty; the rest you carry by hand. Nothing else passes between generators, so anything not listed here is yours to decide independently.
| From | Value | Into | Field | How |
|---|---|---|---|---|
| Waistband | Finished width | Belt loops | Length | Automatic, but only after you save the waistband in this session |
| Trouser block | Waist you drafted to | Waistband | Waist | By hand |
| Trouser block | Rise you drafted | Zip fly | Zipper length | By hand — pick a zip that suits the rise |
| Trouser block | Front width at the pocket line | Slant pocket | Bag width | By hand |
| Your own choice | Seam allowance | All six | Seam allowance | By hand — use one value everywhere |
The order matters because of what you have to read off one draft before you can fill in the next, not because the generators talk to each other. They do not.
Draft this first: it is the only piece that fixes waist, hip, rise and leg line, and every number you carry forward is read off it. Note the dart mode you chose — the default is no darts, in which case the drafted waist matches the measurement you entered. Pick a back or front-and-back dart mode and the drafted waist line grows by the dart intake, which is the figure the waistband then has to match.
Open the generatorDrafted from its own zip length, overlap and shield widths — it never sees your trouser front. Which is why you draft the block first: measure the front rise on your printed block and choose a zip length that ends above the point where the crotch curve turns, then enter that length here.
Open the generatorSized from its own opening inset, side drop and bag dimensions. It has no knowledge of your trouser front, so you decide where the opening sits and check the bag width against the room your front actually has between the pocket opening and the centre front.
Open the generatorSame again: opening length, welt width and bag size are its own inputs. If you drafted the block with back darts, mark them on the printed piece first and position the welt clear of them — the generator cannot do this for you.
Open the generatorEnter the waist the block was drafted to, plus the overlap for the closure. If you used darts, measure the waist seam line on the printed block with the darts closed rather than trusting the number you typed into the trouser generator.
Open the generatorThe one handoff the site automates — with a condition. Draft and save the waistband first, then open this from that page or from the link here, and the loop length arrives already calculated from the finished waistband width. Open it before the waistband and no waistband value is filled in: you see whatever you saved for belt loops earlier in this session, or the starting values if you have not. The number is read from your session, not carried in the link. Count and spacing are yours either way.
Open the generatorSix independent drafts means six chances for two numbers to disagree without anything warning you. These are the joins that actually fail.
With no darts, the drafted waist equals your measurement and the waistband follows it directly. With darts, it does not: measure the waist seam line on the printed front and back with the darts closed, add the overlap, and use that. Nothing checks this for you.
Lay the fly piece on the printed trouser front. The zip has to stop above the point where the crotch curve begins to turn — a fly drafted to a generic length on a long rise ends up in the seam.
A slant pocket bag wider than the distance from its opening to the centre front will be caught when the fronts are joined. Compare the two on paper before cutting.
Only applies if you drafted with darts. The welt has to sit clear of both dart legs along its whole width, not just at its centre.
Each of the six lets you set allowances independently, and each defaults on its own. Choose one value and enter it in all six, or pieces that are the right shape will be the wrong size relative to each other.
Generators size pieces, not yardage. These are working figures for an adult size on 150 cm goods — lay your own printed pieces out to confirm before buying, because rise length and leg width move the total more than size does.
Roughly 1.4–1.6 m for the trousers themselves, plus about 0.2 m for waistband and welts. A one-way fabric — nap, pile or a directional weave — needs all pieces running the same way, which usually adds 0.2–0.3 m.
A mid-weight woven with enough body to hold a crease: gabardine, a firm twill, wool suiting. Very soft cloth will not hold the pocket openings flat, and the welt will ripple.
Use lighter pocketing cotton rather than the shell fabric. Two bags in suiting add noticeable bulk exactly where the trousers sit closest to the body.
Needed at the waistband, the fly and behind both welts. Cut it while the pieces are still flat — it is far harder to fuse accurately once a seam is in the way.
The drafting order and the sewing order are not the same, and mixing them up is what makes a straightforward pair of trousers difficult.
Fuse all interfacing first, while every piece is flat and unattached.
Put both pockets in while the fronts and backs are still separate panels. Every pocket is easier on a flat piece than inside a tube.
Build the fly next, before the crotch seam is closed. Once the fronts are joined the fly area is a confined curve and the topstitching is hard to keep straight.
Sew the darts if you drafted them, then the side seams and inseams.
Close the crotch seam last of the body seams, in one pass from front to back.
Position the belt loops on the trouser top edge before the waistband goes on, so their lower ends are caught in that seam. Attach the waistband, then fold each loop up over the finished band and bartack the top end.
Hem last, after a fitting — leg length is the one measurement worth confirming on the body.
These are specific to assembling these six pieces, rather than general trouser advice.
They share one value, only in one direction, and only once the waistband has been saved in the same session. Every other number on this page is one you carry across yourself, and nothing warns you if you do not.
With darts the drafted waist is no longer the measurement you typed in. Measure it off the printed block instead of assuming, or the band comes out short at the very end of the project.
It can be done, and it is unpleasant. Sew the fly while the fronts are still two flat pieces.
Easy to do when six pieces are drafted across six sessions, and it shows up as pieces that will not line up along the seams that are meant to match.