1. Begin with an origin point located at the top of your paper some distance for the left edge. Draw a horizontal line through this point and stretching out both sides of the origin point, slightly more than about half the hip width – this is the waist line. In these instructions, both the front and back panels are presented on the same sheet of paper – in practice, it will probably be easier to do these on separate sheets of paper, as finding paper wide enough to accommodate both is difficult and working with such wide paper is also awkward. You will need quite long sheets of paper to accommodate the full length of the leg.

 2. From the origin point, measure downwards for the crotch depth (also called the body rise), place a point here (A) and connect with the origin point (a vertical line). Draw in a second horizontal line at this location – this is the crotch depth line. If you don’t know the crotch depth, you can estimate it from the waist measurement as follows : (Metric) Crotch Depth (cm) = 0,175*Waist(cm)+15,4 cm ; (Imperial) Crotch Depth (in.) = 0.175*Waist(in.)+6 in.

 3. Measure the waist-to-hip 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 waist-to-hip measurement is a difficult one to make precisely, whereas the crotch 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 crotch depth line to the hip line, the distance may seem very small.

 5. Now measure from the point A (the crotch depth point) down half the distance to point C (the bottom line), subtract 5 cm (2 in.) and draw in a final horizontal line the same width as the others, at point D – this is the knee line.

 6. 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 and the one on the right for the back panel.

 7. On the Front Leg Panel, from point A (the crotch depth line), measure 1/12 of the hip measurement and add 1.5 cm (9/16 in.) 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.

 9. On both leg panels, measure an additional one 1/16 of the hip measurement plus 0.5cm (3/16 in.) 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 measurements will need to be transferred from the Front to the Back Leg Panel). Now we shall focus on the Front Leg Panel. Draw a point (point I) at a distance of 1/4 of the hip measurement plus 0.5 cm (3/16 in.) to the right of the point F on the hip line.

 10. Still working on the Front Leg Panel, mark the point 1 cm (3/8 in.) 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.)

 11. Continuing on the Front Leg Panel, draw in a small diagonal, inward pointing line from point E (green line in diagram). For waist sizes of 66cm (26″) or less, the length of this diagonal will be 2.75cm (or 1-1/8″). For waist sizes between 66cm (26″) and 78cm (30″), the length of the segment will be 3cm (1″-1/4). From waist sizes of 78 cm (30″) to 91 cm (36″), the length of the segment should be 3.25cm (1-3/8″). Above waist sizes of 91cm (38″), the segment should be 3.5cm (1-1/2″). 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 crotch 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 centimetre (half an inch) or two, to get a little room to manoeuvre.

 12. Continuing on the Front Leg Panel, mark the point (point K) located a quarter of the waist measurement plus 2.25cm (7/8 in.) to the right of point J. Still working on the Front Leg Panel, construct a dart 10cm (4 in.) long, pointing downwards from the origin point O, with a width of 2cm (3/4 in.) at the waist end.

 13. Mark the point (L) located half the bottom width minus 0.5 cm (3/8 in.) to the left of the point C. You can estimate the trouser bottom width by using the following formula: (Metric) Trouser bottom width (cm) = 0,125*waist (cm) + 13cm; (Imperial) Trouser bottom width (in.) = 0,125*waist (in) + 5 in. Make a note of this distance, as you will need to transfer it to the Back Leg Panel.

 14. 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 (1/2 in.). For waist sizes between 78cm (30 in.) and 91cm (36 in.), add 1.5cm (5/8 in.) rather than 1.3cm (1/2 in.). For waist sizes from 91cm (36 in.) to 103cm (40 in.), add 1.7cm (3/4 in.) instead of 1.3cm (1/2 in.). For larger waist sizes, add 2cm (7/8 in.) instead of 1.3cm (1/2 in.). 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. The largest deviation from the line between M and H should not exceed 0.5cm (3/16 in.).

 15. 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. The curve from point P to point I should deviate outwards by a maximum of 0.5cm (3/16 in.). 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.

 16. On the Back Leg Panel drawing, mark the point Q located one quarter of the distance from point E to point A along the crotch 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 crotch depth line (point Q) and the waist line (point S).

 17. On the Back Leg Panel drawing, mark the point U, located 2cm. (3/4 in.) to the right of point S. Then mark the point V, located 2 cm. (3/4 in.) 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 4.25cm (1-5/8 in.), and draw a line between points V and W. This line will slant downwards to the right.

 18. 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 0.5cm (3/16 in.).

 19. Construct a diagonal segment (shown in green in the diagram) from point Q, of length 4cm (1.6 in.) for waist sizes below 66cm (26 in.). For waist sizes between 66 cm (26 in.) and 78 cm (30 in.), set the length of the diagonal to 4.25cm (1.7 in). For waist sizes between 78 cm (30 in.) and 91 cm (36 in.), set the length to 4.5cm (1.8 in). For waist sizes above 91cm (36 in.), set the length to 4.75cm (1.9 in.). Then draw in a straight line from point T to point, and a curved line from point Y to point T, passing through the end of the diagonal constructed line as described above.

 20. 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 1.5cm (0.6 in.), along the hip line.

 21. 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 1cm (3/8 in.). 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 1cm (3/8 in.). 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, deviating outwards by about 0.5cm (3/16 in.).

 22. 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 1cm (0.4 in.). Mark in the point AD located the same distance as the point P is from point D on the Front Leg Panel block, plus 1cm (3/8 in.). 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 (3/16 in.).

 23. 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 12cm (4-5/8 in.) long and 2cm (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 10cm (4 in.) and width 2cm (3/4 in).

 24. Finally, on the Back Leg Panel only, connect points AA and AC with a curved line that deviates downwards 1 cm (3/8 in.) from point C.

  25. Draw over the outlines of both leg panels to finish up. These are usually cut out, as these are now in a format ready to be further manipulated to make variations on classic women’s trousers