First things first, you will need:
 Your body and a tape measurer
 A ruler, preferably a long one such as a meter stick, pattern master or set triangle
 Pattern cutting paper or large pad of paper or several sheets of printer paper taped together.
 Pencils and rubber
 A curve ruler or template, specifically one designed for creating curves like the hip curve
I work in CM, so these measurements will be in metric.
OK, let's begin...
Note: When doing this, it will be easier to draft each individual leg on seperate pieces of paper, as finding paper wide enough to accommodate both is difficult and awkward. You will need quite long pieces of paper to accommodate the full length of the leg, so if you haven't got pattern paper, I suggest tape two or more large sheets of paper together.
Step 1: Mark Your Origin. Orient your paper in portrait orientation, or with the longest dimension running vertically in front of you. Mark a point in the top left hand side, quite some distance from the left edge of the paper. This is your origin point, your home base, and most of your measurements and lines are going to be based on this point. Mark this point O. To establish the waistline, draw a horizontal line through this point and stretching out both sides of the origin point, somewhat more than about half the hip width.
OK, let's begin...
Note: When doing this, it will be easier to draft each individual leg on seperate pieces of paper, as finding paper wide enough to accommodate both is difficult and awkward. You will need quite long pieces of paper to accommodate the full length of the leg, so if you haven't got pattern paper, I suggest tape two or more large sheets of paper together.
Step 1: Mark Your Origin. Orient your paper in portrait orientation, or with the longest dimension running vertically in front of you. Mark a point in the top left hand side, quite some distance from the left edge of the paper. This is your origin point, your home base, and most of your measurements and lines are going to be based on this point. Mark this point O. To establish the waistline, draw a horizontal line through this point and stretching out both sides of the origin point, somewhat more than about half the hip width.
Waistline 
Step 2: Crutch depth line. From the origin point, measure downwards the crutch depth (also called the body rise), and mark A. Connect with the origin point, drawing in a horizontal line at this location  this is the crutch depth line.
* If you need to estimate the crutch depth measurement, you can get it from the waist measurement by multiplying 0.175 by waist measurement and adding 15.4cm*
Step 3: Hip Line. Measure the waisttohip distance downward from the origin point O (point B) and draw in a third horizontal line of the same width as the other two  this is the hip line.
*There is an important issue here The waisttohip measurement is a difficult one to make precisely, whereas the crutch depth (body rise) is much more precise, even when estimated using the formula given in the previous step. Sometimes when one comes to construct the curve from the crutch depth line to the hip line, the distance may seem very small. If this is the case, DO NOT TAMPER with the crutch depth line. Instead, slide the hip line upwards a small distance. The location of the hip line being fairly uncertain, this will give an appropriate curve. If you lower the crutch depth line, you will create a VERY deep crotch. Unless you want this, stay clear of such a change*
Crutch depth line and hip line 
Step 4: Waist to floor. Now measure the waisttofloor distance, downwards from the origin point and make another horizontal line at point C. This is the bottom line of the pants. Even if you a planning to make the legs shorter than their full length, you will still need to place this line as a guide.
.
Step 5: Knee. Now measure from the point A (the crutch depth point) down half the distance to point C (the bottom line), subtract 5 cm and draw in a final horizontal line the same width as the others, at point D.
Waisttohip and knee 
Step 6: Basic framework. We now have the basic framework for the pant leg, whether front or back. We need to copy this framework over to our second sheet to prepare the back panel. The diagram shows the two frameworks side by side, the one on the left for the front panel, the one on the right for the back panel.
Basic trouser framework 
Step 7: Front crutch line. On the Front Leg Panel, from point A (the crutch depth line), measure one twelfth (1/12) the hip measurement and add 1.5 cm towards the left (point E). Draw a vertical line from here upwards to the waist line (point G), passing through the hip line at point F.
Step 8: Back crutch line. Copy the same structure (or repeat the process) for the Back Leg Panel.
Front and back crutch line 
Step 9: Crutch curve. On both leg panels, measure an additional one sixteenth (1/16th) of the hip measurement plus 0.5 cm further to the left of point E and place a marker point (point H).
This is the last point common to both the front and back leg panels. All further manipulations will be different for the front and back leg panels (although a few measures will need to be transferred from the Front to the Back Leg Panel).
Step 10: Hip. Now we shall focus on the Front Leg Panel. Draw a point (point I) at a distance of one quarter (1/4th) of the hip measurement plus 0.5 cm to the right of the point F on the hip line.
Crutch curve and hip 
Step 11: Center front. Still working on the Front Leg Panel, mark the point 1 cm to the right of point G along the waist line (point J), and connect points F and J with a straight line. This is the seam that will usually be used for a fastener (zipper, buttons, etc).
Center front line 
Step 12: Crutch curve. Continuing on the Front Leg Panel, draw in a small diagonal, inward pointing line from both point E (green line in diagram).
*For waist sizes of 66 cm or less, the length of this diagonal will be 2.75 cm. For waist sizes between 66 cm and 78 cm, the length of the segment will be 3 cm. From waist sizes of 78 cm to 91 cm, the length of the segment should be 3.25 cm. Above waist sizes of 91 cm, the segment should be 3.5 cm*
Connect points H and F with a curved line (near horizontal at H, near vertical at F) that passes through the end of the diagonal segment constructed above. If the distance between the crutch depth line and the hip line is small, you may have trouble drawing a reasonable curve. This is where you may want to slide the hip line up a centimeter or two, to get a little room to manoeuvre.
Crutch curve 
Step 13: Front dart. Continuing on the Front Leg Panel, mark the point (point K) located a quarter of the waist measurement plus 2,25 cm (7/8 in.) to the right of point J. Still working on the Front Leg Panel, construct a dart 10 cm (4 in.) long, pointing downwards from the origin point O, with a width of 2 cm (3/4 in.) at the waist end.
Dart 
Step 14: Bottom/hem width. Mark the point (L) located half the bottom width minus 0.5 cm to the left of the point C. . Make a note of this distance, as you will need to transfer it to the Back Leg Panel.
* If you need to estimate the bottom width measurement, you can get it from the waist measurement by multiplying 0.125 by waist measurement and adding 13cm*
Step 15: Inside leg. Mark the point M to the left of point D on the knee line, the distance from point C to point L (determined in previous step), plus 1.3 cm.
*For waist sizes between 78 cm and 91 cm add 1.55 cm rather than 1.3 cm. For waist sizes from 91 cm to 103 cm, add 1.7 cm instead of 1.3 cm. For larger waist sizes, add 2 cm instead of 1.3 cm*
Keep a note of the distance between points M and D, as you will need this for the back leg block. Draw a straight line between points L and M. Note that you should still be working on the Front Leg Panel. On the Front Leg Panel, draw a curved line between points M and H.
Inside leg 
Step 16: Outside leg. For the Front Leg Panel, mark point N on the bottom line at the same distance to the right of point C as was L to its left, and point P on the knee line, at the same distance to the right of point D as M was to its left. Draw a straight line connecting points N and P. Draw a curved line from point P through its maximum deviation at point I and then curving in to point K at the waist line.
This completes the construction of the Front Leg Panel. Put this drawing to one side  now we are going to finish the work on the Back Leg Panel.
Outside leg 
Step 17: Center back. On the Back Leg Panel drawing, mark the point Q located one quarter of the distance from point E to point A along the crutch depth line. Draw a vertical line from this point (point Q) through the hip line (point R) to the waist line (point S). On the Back Leg Panel , mark the point (point T) midway between the crutch depth line (point Q) and the waist line (point S).
Center back 
Step 18: Back waistline. On the Back Leg Panel drawing, mark the point U, located 2 cm to the right of point S. Then mark the point V, located 2 cm above the point U. For the Back Leg Panel, locate the point W along the waist line at a straight line distance from point V of one quarter of the waist measurement plus 4.25 cm and draw a line between points V and W. This line will slant downwards to the right.
Back waistline 
Step 19: Crutch curve. Mark point X, one half of the distance between point H and point E but to the left of point H. Mark the point Y just below the point X by a distance of 0.5 cm.
Crutch curve 
Step 20: Construct a diagonal segment (shown in green in the diagram) from point Q.
* For waist sizes below 66 cm, set the length to 4cm. For waist sizes between 66 cm and 78 cm, set the length of the diagonal to 4.25 cm. For waist sizes between 78 cm and 91 cm, set the length to 4.5 cm. For waist sizes above 91 cm, set the length to 4.75 cm. Then draw in a straight line from point T to point V, and a curved line from point Y to point T, passing through the end of the diagonal constructed as described above*
Crutch curve 
Step 21: Hip. For the Back Leg Panel block, mark the point Z to the right of point R a distance of one quarter the hip measurement plus 1.5 cm along the hip line.
Hip 
Step 22: Inside leg. On the Back Leg Panel block, draw in the point AA located the same distance as the point L is from point C on the Front Leg Panel block (this is the first of the distances you noted earlier), plus 1 cm. Mark in the point AB located the same distance as the point M is from point D on the Front Leg Panel block (the second of the distances you noted earlier), plus 1 cm. Draw a straight line connecting points AA and AB on the Back Leg Panel drawing. On the Back Leg Panel block, draw a curved line from point AB to point Y.
Inside leg 
Step 23: Outside leg. On the Back Leg Panel block, mark the point AC located the same distance as the point N is from point C on the Front Leg Panel block, plus 1 cm. Mark in the point AD located the same distance as the point P is from point D on the Front Leg Panel block, plus 1 cm. Draw a straight line connecting points AC and AD on the Back Leg Panel drawing. Then draw a curved line from point AD through its outer extremity at Z and inward to point W. The deviation outwards at Z should be about 0.5 cm.
Outside leg 
Step 24. Darts. On the Back Leg Panel block, mark the point one third of the distance
from V to W, and draw in a downwards line from this point perpendicular
to the line connecting points V and W. On the Back Leg Panel block,
construct a dart 12 cm (45/8 in.) long and 2 cm (3/4 in.) wide at this
location.
Another third of the way down the line from point V to point W, construct a second perpendicular line. On the Back Leg Panel block, construct a second dart at this location, of length 10 cm (4 in.) and width 2 cm (3/4 in).
Another third of the way down the line from point V to point W, construct a second perpendicular line. On the Back Leg Panel block, construct a second dart at this location, of length 10 cm (4 in.) and width 2 cm (3/4 in).
Step 25: Bottom width/hem. Finally, on the Back Leg Panel only, connect points AA and AC with a curved line that deviates downwards 1 cm from point C.
Back hem 
Ta da! Here is the finished trouser block.
The final trouser block
(These instructions are taken from Gedwoods of Burdastyle.com. I have simply rewritten them for ease of reading).

This is very informative, thank you
ReplyDeleteThanks! Glad you found it helpful xx
ReplyDeleteHi,
ReplyDeleteI love the way you simplified this block. Is there anyway you can help me with drafting these pants with a "Low" waist, and "No" waistband.
Thanks for posting this information. It is easy to understand.
ReplyDeleteThis is great! Thanks a lot :)
ReplyDeleteI understand that this is for woven items. How much would you have to change (or what would be different) to draft for trousers with stretch?
ReplyDeleteYou would have to change the block quite a lot to account for the stretch. If you still need help with this, feel free to send me a message.
DeleteI'm a little late to the party, but where do the back darts come from? Im almost finished with the block just missing these darts
ReplyDeleteIs there anyway you can explain how to draw the back darts? I followed the rest of your instructions and they're very clear until just the end!
ReplyDeleteHi Linda, sorry for the late reply. I have now updated this post so it should give you information regarding the back darts.
Deletedoes anyone know if the developer is still responding to questions I was just wondering
ReplyDeleteHi, yes i do still respond to questions Barbara! I've just been working on a new website so once everything is up and running the blog will move over to the new one. Do you need help with anything in particular?
Delete