How to Draft Stereo-butt/Non-mono-butt Jeans

Any of you who are members of Kathleen Fasenella's forum at will probably have come across the posts about jeans and the dreaded "mono-butt". Naturally I wanted to draft a pair of jeans that did not have this fitting faux pas, and set about figuring it out.

It's is my philosophy that simplicity is best, and if something seams difficult you're probably doing it wrong and over-complicating it. As it turns out, drafting trousers that fit is amazingly simple. It is best done starting from a pencil skirt pattern with at most 3cm total hip ease. I tried 6cm and the result was less than pleasing.

The measurements you will need are:-
  • Waist + 1 or 2 cm ease
  • Hips + 0-3cm ease
    To take a comfortable and flattering hip measurement if you have a round abdomen, put a magazine over your front, hanging down like a little apron and measure your hips over that. This will give you a smoother fit there and avoid the "maternity jeans look."
  • Waist to hips
  • Crotch Depth:
    There are two ways to take this measurement: one that automatically includes ease, and one that has no ease. To take this measurement with ease included, side on a hard flat surface in your tights/pantyhose and take the measurement from your side waist, over the curve of your hip, down to the surface.
    To take the crotch depth measurement without ease, sit on a hard, flat surface, and measure upto your waist level, perpendicular to the table. In other words, do not take the tape measure against the curve of your hip. It must be straight. This method gives a closer fit, and therefore helps avoid the monobutt.
  • Side seam length
  • Knee
    Take this measurement around your bent knee.
  • Foot entry
    To take this measurement, pose your foot as though to put on a long boot, and measure round the heel and in-step. For skinny jeans, you can subtract an inch or two from this measurement, as long as you are using very stretchy fabric, or a zip at the hem.
  • Dart (formula and distribution to follow)

The equipment you will need is minimal:-
  • A straight ruler
  • A square (a piece of card will do)
  • A French curve
  • Thick paper such as brown parcel paper or marked pattern paper
  • Something to hold the paper down if it sticks up
  • Sewing kit

How to Work Out Your Waist Dart

The formula is very simple, though it helps for certainty's sake to use a calculator, and it's easiest in metric (sorry USA).

Now that you have those things and measurements, you can draft your...

a -- b = Waist to hips. Square across from a and b

a -- d = (hips + ease) divided by 2 (because this is half a pattern)

b -- c = a -- d

b -- e = one quarter of hips + 1cm ease

a -- f = one quarter of (waist + ease) + one dart

d -- g = one quarter of (waist + ease) + two darts

h and i are 1.2cm (1/2 inch) up from f and g respectively

j is 2cm down from a (this may just be me, but my clothes are more comfortable with this adjustment)

a -- k = crotch depth

square down from e and c to l and m respectively

And that's it. Now cut it out and cut the line e -- l so that you have a front pattern and a back pattern.

Now we shall turn our patterns into jeans pattern...

First we'll add the waist-line darts 

(I bet you thought I'd missed them out!)

FRONT: Divide your dart measurement into 3. The dart will be two thirds, and the CF will be shaped by one third. E.g. If your dart measurement is 2.4cm (mine is):
            2.4cm/3 = 0.8cm = front shaping,
            2 x 0.8cm = 1.6cm.

So shape the CF by making a point 0.8cm in from the CF waist, and connect to the CF hips with an outwardly curved line. (This makes a better fit over a naturally round abdomen). Taking this as the new CF waist-point, measure a straight line from their to the side waist-point. Divide this into three and mark the point nearest the side waist. Square down from here 10cm. Make your dart on this line, here 0.8cm from each side. For a nicer fit, make the dart legs curve outwards slightly, or if you have a full tummy, curve them inwards slightly.

BACK: The total back shaping is 2 darts worth. This will be divided into 5 to give two darts and some CB shaping. E.g. using the 2.4cm dart again:
            2 x 2.4cm = 4.8cm = Total back dart shaping
            4.8cm / 5 = 0.96cm (near enough to 1cm for practical purposes) = Back shaping
            1cm x 2 = 2cm = Dart (and there are two darts, each 2cm)

So shape the CB by making a point 1cm in from the CB, and draw with an inwardly curving line to the hip point. This accommodates the shape of the spine. Taking this as the new CB waist point, measure straight to the side waist point and divide into thirds, marking each for a dart placement. Square down from each, 12cm for the one nearest the side, and 14cm for the one nearest the CB. (NOTE: These darts lengths are only guideline measurements, yours may be different.) Make a dart on each line, in this case 2cm side. Curve the dart legs outward to work better with the curve of the lower back.

Now we'll add the front crutch extension.

Extend the CF Crotch depth line by 1/5 of the pattern's front hip measurement (k-l). Connect this point straight to the CF hip point. Slide your square along this line until the other part of it meets the CF crotch (k). Connect straight. Divide this line into three equal parts. Draw a curve from b through the point nearest outer line, to the crotch point. (As illustrated.)

Now for the back crutch extension.

The difference between different types of trousers/pants, as far as pattern-cutting is concerned, is the length of the back crutch extension, and the height of the pitch. The pitch is the wedge you can see in the illustration, under the Crotch Depth line. The shorter the back crotch extension, the greater the pitch must be to make up for the loss of crotch length and let you wear the trousers/pants without doing yourself an injury.

Coco Chanel said that "Fashion is architecture: it all a matter of proportions." I think the same applies to sewing patterns. Why should we use "standard" measurements for pitch and so on and then fix the fit, when we can use a measurement proportionate to our own measurements and then have a nearly perfect fit right away?

Crotch extension and pitch must be in proportions to each other and to our hip size. We use 10th of our pattern's back hip measurement as unit (we'll call it x). In jeans or slacks we want a total of 5x. Trousers have a looser fit, which you can see if you Google Metric Pattern Cutting for Women's Wear and look at people's blog photos. They look more like men's trousers and are not altogether flattering on women, so I don't wear them.

  • Slacks:        Crotch : Pitch = 4x : 1x
  • Jeans:         Crotch : Pitch = 3x : 2x
  • Trousers:    Crotch : Pitch = 5x : 1x

So get your compass out and set if for a radius of 2x, and draw a circle from point m. Then draw a straight line from l the length of l -- m, touching the circle. Extend this line by 3x to give the crutch extension. Squared down 0.5cm to 1.5cm (about 1/4" to 5/8") from this point mark a new point that will be the crotch point. (By the was, this will make the back trouser leg shorter on the inseam than the front-trouser leg, and when this piece of fabric is stretched to match the front one, it will give a better fit. The more contoured you want this area to be, the lower you must drop the point.)

From the new crotch point, draw a straight-line up to the hip line. Slide your square along this line until its other arm touches the CB on the crotch line. Draw this line and divide it into three. As you did for the front crotch curve, draw from the hip line, through the point nearest the line, and to the crotch point with a curve.

Now it is time to draw the legs (rather important for trousers/pants!)

FRONT: This is simpler than the back to explain. Mark a point half-way along the crotch line and square down. From top to bottom, this should be your side waist-hem length (we'll say side-waist to ankle). Divide that in half and mark. 4cm up from that mark you knee line. This is where your knee measurement comes in.
Bend your knee as far as it will go, and measure. Mine is 40 cm, but I like a closer fit, especially with stretch denim slim jeans, so I will reduce it to 36cm. This allows you wearing ease. Divide that by 4 (9cm) and subtract 1cm. Measure this distance out from each side of the knee marking on your pattern. Connect straight to the crotch point and the side hip. Curve the lines so that they look right, i.e. inwards by about 0.8cm on the inseam, and by about 0.6cm or so on the outseam.

At the hem line you will need your entry measurement. To get this, pose your foot as though putting it into a really narrow calf-length boot, and measure around the heel and bridge. (One me about 30cm.) You will need the hem of your trousers/pants to be at least this, or else you won't be able to get your foot through. (A lot of good that would be!) Divide this measurement by four and subtract 1cm. (6.5cm) Measure this far out from the hem marking on your pattern. Connect to the knee point. Blend the knee if necessary.

BACK: The line that you had as the Crotch line, after pitching and before lowering the crotch point is the line you will use for drawing the leg, so find its centre point and square down the same length as it is on the front pattern. Copy the placement lines for the hem and knee.

For the knee width, divide the knee measurement by 4 and add 1cm, here giving 10cm. Measure this much out from the knee point. Connect to the crotch point and the side hip point, curving the lines inward so that they look right to you. (At least as much as you did for the front leg, and not more than about 1cm each more).

For the hem width, divide the hem measurement my 4 and add 1cm, giving me 9.5cm. Measure this much out from the hem point. Connect to the knee and blend if necessary.

NOTE: The centre leg lines are also the grainlines.

So that is your jeans-fit pattern. Now you can change it into a pattern for jeans. You will probably want to trace it first in case of mistakes, or tea-spillage. It is a good idea to copy it onto thick, tough paper, fold it up neatly, and store it in a plastic sleeve.

Making your trouser/pants pattern into a jeans pattern

The rest of the pattern-making is pretty much just drawing, closing darts, and adding seam allowances.

Draw on the pockets as shown, add the fly (3cm wide), add the waistband (I made mine 3cm, but you can have whatever you wish).

The front pocket is the most complicated thing, because there are so many layers. There is the pocket bag/facing, the inner pocket bag, and the piece that you will see (I'm not sure what it's called, but it's the bit made of denim and in the illustration, it's red).

First, draw the pocked shape, which needn't the traditional shape, but that is easier to sew than, say, a heart shape. The thing-with-no-name extends a bit into the pocket (say 1.5 - 2cm) so that it doesn't peek out when you are wearing the jeans. Trace this piece off and add seam allowances.

Then there is the inner pocket bag, to which the thing-with-no-name is sewn. Using the line you just added for the inner edge of the thing-with-no-name), draw the inner pocket bag (the pink bit in the illustration).

Now for the pocket-bag/facing. Trace the pink bit but go up to the original pocket line instead of the inner one. This is what will be sewn to the outer denim.

Now add seam allowances.

Now for the waistband.

The front waistband will need two pattern pieces: one for the left and one for the right, because one side will have an underlap for the button to go on. Trace off the waistband and close the darts by folding the paper so that the lines meet at the top and bottom of the waistband.

Now trace a copy of this and we will make a waistband for the other side, with an underlap. On your traced copy, fold the paper along the CF and trace as far as the fly stitching line. This extra bit is the underlap. Now open it up and add seam allowances all around the waistband pieces.

Now to do the back waistband. This is easy. You just do the same as you did for the front waistband without the underlap (because the back doesn't have an opening).

Now for the fly

You have a choice here. You can either fold back the paper on the front of the pattern and trace the stitching line, then add seam allowances; or you can trace it off separately and make a fly like you get on RTW jeans. I went with the first option and sewed it like a large lapped zipper (sewing instructions here). It's easier and less bulky.

After that it's just a matter of the pockets, seam and hem allowances, and sewing. On mine I had to slim the hips. Apparently I have very slim hips. And I somehow lost about 3cm on my waist over Christmas (I don't know how; I sat around for most of it) so that threw off the fit of my toile a little at the CF waist. Never mind.


As for yardage, I only needed about 1.5 metres of stretch denim, which is about half of what was suggested on a Vogue jeans pattern on-line. (I bought 3m so I may have enough to make a jacket, if not, then I can make a skirt or another pair of jeans). I am petite and about a size 10 or so on my hips (pattern size), so most people may need more. You will also need some lightweight cotton fabric for the pocket linings, and optional back pocket appliqué (I have a butterfly). The belt loops can be made out of scraps.

I can't give visual sewing instructions because I have only one photograph and that's not much use. You can either use your good sense and experience, or use instructions available in books, online, or in commercial patterns.

Critique of My Own Jeans

Here is a front view and a back view of my finished jeans: 

It is extremely difficult to take a good photo of your own back-view. This was the best I got.

Now, I suspect the crotch depth may have too much ease (it is automatically included when you take the measurement) and that is why my jeans are not super-fitted there, like here. Also, I mistakenly had the front crutch extension being 1/4 of the front hip, instead of 1/5 which is should be for jeans. And they're more of a slim-fit than a skinny fit, but isn't it like magic to be able to draft and sew something right of out your head, and then have it in reality?! (It's so neat!)

And yes, these do look high-waisted. But I am so slim that any jeans not defining my waist will be very unflattering and make me look more columnish. (That is probably not a word, but never mind.; Shakespeare frequently invented words and if it's good enough for him...)

To prevent the waist from stretching (I used stretch denim and don't want it to stretch at the waist) I sewed the waistband seams with cotton tape in them. After only being able to buy jeans that slip down, it's nice to have pair stay on my waist!

Version 2.0

I made another pair with a shorter crotch depth (measured to omit ease), and a shorter front crotch extension (1/5 front hips; the first pair had 1/4 because I forgot that jeans use less than other trousers). I also narrowed the legs and hems a bit, and lengthen the leg. (They will shrink in the wash).

Hard-won Topstitching Wisdom

The topstitching went a bit wrong sometimes, especially when I went over the really thick parts. Note: it is better to sew the belt loops onto the waistband, after topstitching, instead of trying to include them in the waistband seams. Otherwise, it seems, you get a lot of skipped stitches.

Also, it is better to stitch the yoke seam allowance downwards, not upwards, because otherwise you get a funny bump along the back.

And a note on topstitching thread. Don't bother. I got much better results and wasted far less thread by using two spools of regular sew-all thread in a size 100 jeans needle. (A tip I got off Angela Wolf's video on YouTube). Below you can compare topstitching thread when it was working (the seam), and doubled sew-all thread (the double-stitched hem). Apart from the wobbly hem, you can't see much difference, and certainly not from a real-life distance, but it is much easier to sew with doubleed sew-all thread, and you can still use your needle-threader if you use a 100 jeans needle.

If you make some jeans and blog about them, or post them on BurdaStyle, please let me know  -- I'd love to see how they turn out! Also, if this post is well received (and even if it's not) I want to turn it into a Kindle book, so please tell me what you think and if there is anything you want to know. I'll take the post down when I get the book for sale on Amazon.

Sabrina Wharton-Brown
United Kingdom

P.S. You can see more about the monobutt on Kathleen's webpage entitled "Jeans fit so lousy these days".

P.P.S. I didn't prewash the denim, so now they have shrunk in the wash, and while they feel tighter, the fit looks better.

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