Pants patterns are unique because the most important part of the pants is the part that is missing! Most of the shaping takes place in the waist to crotch area where there is no fabric.
- Crotch - Bottom of torso where legs join the body.
- Crotch Depth - The distance from the waist to the lowest point of the crotch. Tailor’s refer to this as the "rise".
- Crotch Length - The distance from the center front at the waist to the center back at the waist passing around the crotch.
- Crotch Extension - The distance added to the front and back of a pattern to allow for the depth of the inner leg.
- Crotch Point - End of the crotch extension lines.
- Crotch Level - The crotch depth distance drawn across the pattern.
- Outseam - Side seam joining the front and back.
- Inseam - Seam between the legs joining the front and back.
There are specific terms for each length of pants.
- Full - These rest on the top of the shoe and extend nearly to the ground at the heel. The goal is to stay off the ground, so the pants hem doesn’t get dirty or wear excessively.
- Ankle - These stop at the ankle and expose the entire foot/shoe. Most designs hug the ankle using a cuff or elastic on a full width leg or using a close-fitting leg and knit fabric.
- Capri - These stop 1" (2.5cm) above the ankle and usual incorporate a close-fitting leg. They are also known as clam diggers, crop pants, three-quarter pants and mid-calf pants.
- Toreador - These stop halfway between the knee and ankle. This name comes from the pants worn by bullfighters.
- Pedal Pusher - These stop 2" (5cm) down from the knee. The name most likely comes from pants designed to be worn when riding bicycles. This same location is used for knickers.
- Knee - These stop at the knee, but are not a popular design option, as it isn’t a very flattering position.
- Bermuda - These stop halfway between a Jamaica and a knee length.
- Jamaica - These stop halfway between the crotch and the knee.
- Shorts - These stop 2" (5cm) below the crotch level.
- Short Shorts - These are drawn with a diagonal hem and are located 1.5" (3.8cm) below the crotch of the inseam and 1" (2.5cm) to 1.5" (3.8 cm) above the crotch at the outseam (side seam).
Varying the depth of the crotch can change the design drastically. Knit leggings and skinny jeans have a shallow crotch depth and hug the body tightly. Overalls, pantsuits, culottes and hip-hop designs increase the crotch depth. In the case of overalls and pantsuits, this is done to provide additional room when the arms are lifted. In other cases, it is done to make the pants appear baggy for design purposes only.
Fit & Flare
How the pants hug the butt and stomach has a lot to do with design. Loose fit, like culottes, hang away from the butt in the back and the stomach in front. Trousers hang down straight from the most prominent point on the butt and stomach.
Slacks cup under the butt slightly and follow the line of the stomach. Jeans follow the contour of the butt and stomach. Leggings are completely form-fitting following every curve.
Leg widths are completely subjective. They can vary from form fitting to extremely loose.
Bell-bottoms are a slim fit on the top following by a flare at the bottom. If you want to create pant legs that flare only at the bottom, add a point where the transition will occur using the exact same distance on the inseam and outseam of the front and back. The transition point can be above, at or below the knee. Now spread the bottom points at the hem further apart.
Locating the natural waistline for your model, particularly males, can be a bit of a challenge. The general rule is that this line should be about where the elbow is when the model's arm is relaxed at the side. You can choose a point anywhere from there to the belly button. This is the location for your waist measurement used to draft the bodice / top patterns.
This location is not ideal for pants. It can place the waistline of the pants much higher than you typically want. Refer to the image to see the different waistline height levels for pants.
As you can see, the natural waistline is where most of us would consider "old man" pants to rest. The Typical Pants Waistline is where most of us would choose, if not lower.
Darts & Yokes
Pants usually have darts at the back waist because there is a big transition from the waist measurement to the hips.
Darts in the front of the pants can be used for shaping, but are more often used as a design element. Many times the dart is closed not by sewing it shut, but by pleating the excess. Slacks and trousers often have one or two pleats in the front.
The darts in the back can be replaced with a yoke, like a pair of jeans. The back pants pattern is cut, usually on a slight diagonal, at the top. If there is a waist dart, the dart is rotated closed. Pants yokes are generally left in two pieces, since the center back seam lines up with the center back of the pants.
The method you choose to close your pants depends on the design. In order to put on a pair of pants, the waist has to pull over the thighs and hips. You can use a split method, which means the pants separate at the waist or a closed method with no split.
If you are making pants made of knit, you don’t have to add a split closure. Also, if your pants are as wide or wider at the waist than your model's hips, you don’t need a split. You can use an elastic waist or drawstring for pants patterns wider than your model's waist.
For all other pants designs, you will need to split the waist open. You can put this split at the side seam, center back or center front. How you close the split depends on your design. You can insert a zipper, use buttons or any other type of fastener.
The most common type of split closure for pants is using a zipper at center front with a fly. The construction of a pants fly is rather complicated because you have to create an overlap very similar to a button extension on a shirt.
This overlap, called a fly extension, can be part of the pants pattern or a separate piece. There are extensions on both sides, right and left. The left front extension is used as a lining and the right front extension is cut on the fold and then folded when sewn in place to finish raw edges.
The left side of the pants will overlap the right when creating flys and waistbands for men and women.
All pants have a waistband. Sometimes these are sewn on as a separate piece and other times they are just an extension included in the pants pattern. Waistbands that are separate are typically one long piece with one seam.
If you are creating pants with an elastic or drawstring waistband, the ends should meet at center back. Zippered closures usually have a waistband that overlaps with a button or snap. This includes pants with a fly placed at center front.
Even if your zipper or other closure is not visible, there should be a waistband overlap where the slit is. You’ll need to secure the overlap to the other side using a button or a small seam to keep it closed.
Most pants facilitate a belt, which means you’ll need some belt loops. The number of belt loops varies with the design. Five belt loops is quite common, with loops placed at the center of the waist on the front left, front right, back left and back right. The final loop is placed at center back, often off-center of the center back seam. The placement of loops also depends on the type of pockets you’ve chosen and where they lay on the pattern. You may need to adjust your loop placement.
Belt loops are pieces of fabric cut twice the needed width. The long edges are folded to meet at the center back and pressed. The strip is top-stitched with two rows of stitching. The top and bottom edges are folded over. The loops are placed on the pants and sewn at the top and bottom using a bartack. The top is on the waistband and the bottom is on the pants themselves.