There are more than 500 possible ways to drafting trousers, the waist can be high, normal, under the bust or low waist. The pants can either flare away from your body, hang straight, go around your buttocks or follow the whole silhouette. The length can go from micro to full and the leg shapes can flare more or less. There are endless possibilities when it comes to trousers, so how can you create that design you have been dreaming of?
Table of Contents
Let’s start from the beginning. A pants pattern is divided into two parts:
- The Foundation: refers to the top part of the trousers which covers the torso. The foundation goes from the waist line to the crotch line and defines how much ease there will be around the thighs.
- The Leg line: the bottom part of the pattern. This goes from the crotch line until the hem of the pants. The start of the leg line comes defined by the foundation but from there any shape can be drafted.
There are 4 different Pants Foundations: The Culottes, the Trousers, the Slacks and the Jeans.
On this post I’ll show you the process to draft any trouser foundation you want, but before doing that, there are a couple of technical names we need to address. These will be very important to correct the fit of our patterns.
The Crotch library
Crotch area
The point where the leg separation happens. Where front and back patterns meet.
Crotch depth
This is the distance measured from the waist line until the crotch line.
Crotch length
This is the distance around the crotch area, measured from waist to waist.
Crotch extension
This is the length from the hip line until the crotch point.
Now that these names are clear, let’s look into the different foundations and their characteristics.
The 4 Trouser Foundations
Culottes Foundation
This foundation is based on the skirt pattern. It is the baggiest of the versions and has the deepest crotch depth, longest crotch length and crotch extension. Ease around the thighs should be around 15cm. This foundation can also be drawn using the A line skirt for extra flare.
Trousers Foundation
The Trouser foundation is the one most drafting books come with. This design has a low crotch depth, similar to the Culottes. It also has a comfortable crotch extension and the fabric should hang straight from the abdomen and buttocks. The ease around the upper thigh should be around 9cm.
Slacks Foundation
The Slacks are also known as Chinos. This type of pants has a slightly higher crotch depth than the trousers. In this case, the fabric should slightly shape your buttocks and hang straight from the abdomen. The ease around the upper thighs should be around 5.5cm
Jeans Foundation
The jeans are the foundation that follows the shape of your body the most. The fabric should cup around your buttocks and hug your knees and ankles. There should be enough ease to allow for movement which translate to around 2.5cm around the upper thigh.
These are the four foundations, and you can always modify one to get to another one. Here you can find a summary of how different they are and some approximate values for the thigh ease and crotch extension. Remember that you can always add or remove ease later on.
| Pants Foundations | Crotch extension | Thigh ease |
| Culottes | hip/2 | +15cm |
| Trousers | 3/8 hip | +9cm |
| Slacks | 3/8 hip – 2cm | +5.5cm |
| Jeans | hip/4 | +2.5cm |
Drafting Trousers – Darts
There is always a lot of confusion when talking about darts. Should there be one, two, none? How long should they be? And how wide? Well, I wish the explanation was easy but it’s not! Darts are a way to create 3D shapes on a 2D surface. All our bodies are different so it’s impossible to find a dart method that suits everyone.
If you take me for example, I have a flat stomach and a round buttocks. This means that if I add darts on my front pattern, this will create a round shape that my body cannot fill. Which will translate into extra fabric and wrinkles. The same way, if I have no darts on my back pattern, there will be no space for my buttocks. And if you add two darts, there will be too much shaping and wrinkles, so one dart is my sweat number. As a summary, all my foundations have exactly the same amount of darts: Zero at the front and one at the back. So despite what the book asks for, this is what I always go for.
The same stands for how wide and how long the darts should be. You’ll have to investigate through trial and error. In general, darts should point towards the fullest part and finish some centimetres before that point.
Drafting Trousers – Length variations
Once the foundations are clear, it’s time to define how long the pants are going to be. Every length has a name and they are patterned slightly different than the full length pants.
There are 7 official length variations and these are:
- Shorts-shorts
- Shorts (5cm below crotch)
- Jamaica (1/2 between crotch and knee)
- Bermuda (1/2 between Jamaica and knee)
- Pedal pusher (5cm below knee)
- Toreador (1/2 between knee and ankle)
- Capri (2.5cm above ankle)
When drafting these designs you can use the foundation of your choosing and you’ll have to slightly tapper the leg-line. The longer the design, the more tapering is needed. This stands for all the variations except for the Short-shorts. These also need changes in the crotch curve.
Be aware that these are the official lengths but you can always play around and make them shorter or longer. For example, shorts are too short for my liking and Jamaicas are too long, so I always go in between those two.
Drafting Trousers – Waist lines and Waistbands
Before deciding what waistband is better for your design, you have to ask yourself: “Where do I want the waistband to sit?”. Most books define 3 main levels:
- High waist: It can be as high as you want, it normally sits below the breasts on the empire line.
- Natural waist: Normally it sits at the end of your ribs and it’s the thinest part of your body.
- Low waist: Most drafting books say this should sit 5cm below the natural waist.
If you want my advice, you should ALWAYS pattern your design to fit your natural waist and modify it afterwards. It is way easier to adjust any fitting issues and you can always go to high or low waist from there. You can also make the pants as high or low waisted as you want. Always take into account the shape of your body, sometimes when lowering the waistline, you’ll have to lower the front pattern more than the back.
Once you have defined the waist line, you can choose the type of waist band. There are 3 types of waist bands:
- Straight: It’s a rectangle that uses the length of your waist plus some ease
- Curved: It’s a curve (changes depending on the body) that uses the length of the pants waist and your waist
- Facing: It’s an invisible waistband
Which one you’ll choose depends on the body shape or how high/low the waistband sits. For example, if it sits over the natural waist, a straight band will sit well enough. On the other hand, if you’re working with low waisted trousers, you will probably need a curved waist band. If you plan on using a waistband, I would advice you to use the straight one.
There are a lot of tutorials out there on how to create the curved waistband. I think the BEST way to do it is by using your pattern, adding front and back together and cutting through the darts. That way, the curve will be exactly what your body needs.
Drafting Trousers – Leg lines
Once you have mastered all the other drafting trousers techniques, it’s time to go crazy with the shapes. You’ll notice that every foundation has its own leg line, some more flared and some less. There are 4 main silhouettes: Slim, Tapered, Straight and Flared.
- Slim: This is the most typical style. It’s a shaped seam that follows the shape of your body, getting smaller at the knee and then even smaller at the ankle. You can control the amount of fabric at knee level and at ankle level, this way you can reduce the excess. These levels can also be modified to create a tightening effect around certain areas.
- Tapered: The tapered version draws a straight line from the hipline/crotch to the ankle line. It is very similar to the slim version but this time the control is only on ankle level. This silhouette has more extra fabric under the buttocks compared to the slim version. The same way, if you increase the hem width, that will control the fabric throughout the pants leg.
- Straight: The straight leg line draws a straight line from the hipline/crotch down. In this pants version the width of the hem is given by the length between the hip and the crotch.
- Flared: There are multiple ways to add flare. It can be added at hip level, above the knee, at knee level or below the knee. More or less flare can be added depending on the look you’re going for. There are no standard rules for this, so experiment and have fun. Some designs that use flare are the bell bottoms or the bootcut patterns.
This is a working document and I will keep adding to it the more I learn, so keep it saved! If you want to know more about trousers, drafting techniques or similar, take a look at the posts below and have fun.
