When people talk about fashion design involving a lot of problem solving, you probably didn’t think they were talking about math problems. It’s true, though. The solution to some of the problems you run into in fashion entrepreneurship do involve math.
I was at a fashion industry event earlier this week and was chatting with the parents of one of the designers there. When I described what I do in my job, the mom responded “I didn’t realize there was so much math in fashion!”. It is more math than most people assume and it got me thinking of all the math we do use. Here are just some of the applications for fashion math and the different skills involved.
Costing (Addition + Multiplication)
This bit of fashion math probably seems the most obvious. A cost sheet is where you’ll list out all the things that go into making your product and the costs of each. The costs are then totalled up to get your cost of goods.
Then, the COG is multiplied to get the wholesale and retail prices. It is pretty straightforward math and it is easy to set up a spreadsheet template that does the calculations for you so all you have to do is input the materials and costs.
Yields (Averages)
Yields are a great example of figuring out averages. To accurately calculate how much fabric to buy for your production order, your yield should be the average consumption of all sizes on the order. You (or your patternmaker or factory) can find this exact number by laying out a size run of each style and dividing the needed length of fabric by the number of sizes in the marker. Remember, if your design uses more than one material, you will need to calculate the average yield of each one separately so you have accurate figures to put on your cost sheet.
You can get a quick estimate by averaging just the smallest and largest sizes too. This average yield will end up close to the yield of the middle size in your size range which is why using your middle size as your fit size is convenient. It lets you estimate a yield earlier in the development process before the pattern is graded.
Allocating Materials (Algebra)
You thought you were done with math story problems when you graduated high school, didn’t you? (Don’t worry, these are fun and you end up with pretty clothes at the end.) Say you have a certain amount of fabric left and you have two styles that use that fabric. Given each style’s yield, what combinations of quantities of each style can you make from the remaining fabric? There’s an algebra problem hiding there, waiting to be solved!
I’ve also written algebra problems to figure out the total fiber content percentages in a garment that used two different fabrics with different fiber blends.
Graded Specs (Adding Decimals and Fractions)
The graded spec is part of the tech pack and is a spreadsheet showing what each point of measure measures for each size of your design. Most people write measurement specs as fractions, but pattern software often shows spec measurements in decimals. If you work in fashion, you’ll get good at converting decimals to fractions and at adding them together. For each size up and down from the base size, the pattern grows in varying increments depending on the placement on the body. These fractions show up on the spec chart as they get added and subtracted from either the base size or the size adjacent to it.
Pro tip: work smarter, not harder and create your sizes as formulas based on your base size specs for easy updates. Once it’s set up, the spreadsheet does the math for you. This is how my graded spec chart templates work! You can check them out and get the spec chart templates for yourself here.
Patternmaking (Geometry)
The fit of the garment is shaped by the pattern and the pattern is all based on geometry. Want to know the radius of a circle skirt? Break out the circumference formula. Need to confirm that two seams align smoothly at the edges? Measure their angles and make sure they add up to 180 degrees. Want to maintain the fullness of a flounce, but increase its width? More geometry.
With digital patternmaking like what I do in Optitex, I’m not using my protractor as the software does handle some of this geometry math for you, but the concepts are still very much applicable. I always have my calculator handy while working on a pattern.
Shrinkage (Calculating Percentages)
Before creating a pattern, I always do a wash test on the fabric to check for any shrinkage. I am looking for the percentage of shrinkage in both the width and length directions so I can build that amount into the pattern to compensate. To find this percentage, measure the length and width of your test swatch and subtract that from the original dimensions pre-wash. Now take that difference and divide it by the original measurement and convert that to a percentage.
For example, if my swatch was 10” and shrunk to 9 3/4”. That would be a difference of 1/4”. Divide that 1/4“ by the original 10” to get 0.025. To convert that to a percentage, multiply it by 100 to get 2.5% shrinkage.
So there you go – fashion math 101. Fashion may be seen as a purely creative industry, but there is way more math involved than most people realize. If you run a fashion brand, it doesn’t hurt to brush up on some of your math skills so you can solve any problem that comes up in your brand. Class dismissed.