Sewing tutorial

Re-sizing PDF Patterns Part 1

My favourite makeup bag and brush roll have seen better days. A few years ago (before I had a blog) I sewed a new makeup bag with attached brush roll using a pattern by So-Sew-Easy (Cosmetics Bag And Brush Roll). It’s a great pattern and I’m excited to be using it again. One caveat… I want a slightly smaller cosmetics bag with brush roll for my travel-sized makeup. This post is part 1 of 2 about re-sizing PDF patterns.

Sewn By Tanya Sewing Tutorial: Re-sizing PDF Patterns part 1: 2 different cosmetic bags
Original sized So-Sew-Easy Cosmetics Bag With Brush Roll (top) & Old Cosmetics Bag (bottom)

Most PDF patterns for non-clothing items make 1 size of the project. Sometimes customizing the size to fit your specific needs is mentioned in the instructions. Usually you’re on your own as far as how to do so. I’m going to guide your through my process for re-sizing a PDF pattern to create a custom-sized project. I’m using the So-Sew-Easy Cosmetics Bag With Fold Over Brush Roll as an example. In this case I’m making a smaller version of the project. I have successfully used the same method to make a smaller and larger versions of other projects.

I’m using the following abbreviations:

  • Old-CB = old cosmetics bag (black in colour)
  • F-CB = finished So-Sew-Easy Cosmetics Bag With Fold Over Brush Roll (orange, grey and white in colour)
  • O-Pat = original pattern for So-Sew-Easy Cosmetics Bag With Fold Over Brush Roll
  • R-Pat = resized pattern
  • FCS-CB = finished, custom-sized So-Sew-Easy Cosmetics Bag With Fold Over Brush Roll

Let’s get started.

Step 1) Find the final dimensions and seam allowance of the original project.

The first step to re-sizing PDF patterns is determining the exterior dimensions of the original project. There are 3 ways you can accomplish this.

Refer to instructions

Usually the project’s instructions will provide the final dimensions and seam allowance information. Final dimensions should be near the beginning. Read carefully for the seam allowance information as it may be at the beginning of the instructions or part-way through.

Measure project made with original pattern

While the seam allowance for this O-Pat is stated at 7 mm, the final dimensions of the project weren’t listed. Fortunately I can measure the first cosmetics bag that I made.

Measuring completed So-Sew-Easy Cosmetic Bag
Measuring completed project

I measured my F-CB along the seams. It’s 23 cm wide, 13 cm tall, 11 cm deep at the base and 0.5 cm deep at the top. It has a triangular cross-section.

Make a paper model

If the final dimensions aren’t in the project’s instructions and you don’t have a sample of the finished project, you can still estimate the final dimensions by creating a paper model. Gather the exterior pattern pieces. When the exterior pattern pieces say “cut on fold” I make my paper pattern piece the same size that the cut fabric piece would be.  Similarly, when 2 exterior pattern pieces are needed, I cut a second pattern piece out of scrap paper.

Exterior pattern piece assembled with seam allowance marked
Assemble exterior pattern pieces & mark the seam allowance

Draw the seam allowances on your pattern pieces. Fold the exterior pattern pieces along the seam allowance lines then fold the exterior pattern pieces along the lines the fabric would be folded along. Tape the exterior pattern pieces together to create a paper model of the project that you can measure.

Paper model of So-Sew-Easy cosmetic bag | Sewn By Tanya Sewing Tutorial
Create paper model from exterior pattern pieces

I measured the paper model of my O-Pat along the folds. It’s 23.5 cm wide, 13 cm tall, and 11 cm deep at the base. It also has a triangular cross-section. Taped paper doesn’t add the same amount of depth at the top that a zipper would so I consider these measurements to be “within error” of the measurements I obtained by measuring a finished cosmetic bag.

Step 2) Determine the external dimensions for your custom-sized project

If you have already determined the external dimensions for your custom-sized project, skip ahead to step 4.

If not, you will find the discussion in steps 2 and 3 helpful.

There are two ways to think about pattern resizing:

1) add/substract length along depth, width and/or height

2) multiply the depth, width and/or height by a resizing ratio

My old favourite cosmetics bag (Old-CB) is 17 cm wide, 11 cm tall and 5 cm deep with a rectangular cross section. When filled with my travel cosmetics, the zipper just barely closes. Depending upon the order in which I place things inside it, it doesn’t always close and it’s small size is one of the reasons that I retired it.

Comparing the size of the my Old-CB to my F-CB gave me some insight into the dimensions I would want for my custom cosmetics bag (FCS-CB): it needs to be bigger than 17 x 11 x 5 cm and smaller than 23 x 13 x 11 cm.

Side views of 2 cosmetic bags | Sewn By Tanya sewing tutorial
Cross section view of Old-CB (right) and F-CB (left)
Step 3) Check that the volume of your finished project will be adequate.

If your project is two dimensional, skip ahead to step 4. If not, continue reading.

I can make my customized bag any size in between 7 x 11 x 5 cm and 23 x 13 x 11 cm so long as the volume is larger than the volume of my Old-CB. I calculated the volumes of these 2 cosmetic bags.

Sewn By Tanya Sewing Tutorial: Re-sizing PDF Patterns part 1
Calculate volumes of prisms
Cosmetic Bag Volume Old-CB (black) F-CB (orange, white & grey)
Length (cm) 17 23
Height (cm) 11 13
Depth (cm) 5 11
Cross-section shape rectangle triangle
Volume (cubic cm) 935 1645

A customized SSE Cosmetic Bag with the same dimensions as my black cosmetic bag (length of 17 cm, height of 11 cm and depth of 5 cm,) would only have a volume of 468 cubic centimetres, which is only 50% the volume of my current black cosmetic bag with a rectangular cross section. I added 1 cm to the length, height and depth of the dimension for Old-CB  and calculated the area of the resulting triangular prism (for the SSE cosmetic bag) until I had a volume larger than 935 cubic centimetres. See the below table for the results.

Assessing Potential Volumes Old-CB (black) Potential FCS-CB dimensions 1 Potential FCS-CB dimensions 2 Potential FCS-CB dimensions 3 Potential FCS-CB dimensions 4
Length (cm) 17 17 18 19 20
Height (cm) 11 11 12 13 14
Depth (cm) 5 6 7 8 9
Cross-section shape rectangle triangle triangle triangle triangle
Volume (cubic cm) 935 468 756 988 1084
Assessment Minimum volume too small too small bigger a lot bigger
Step 4) Calculate the resizing ratio for the exterior pattern pieces.

The resizing ratio is the ratio between the dimensions of the custom project versus the original project. The ratio will be less than one if you are reducing the size of your product along any dimension, greater than one if you are enlarging it and equal to one if you are not changing it.

Different re-sizing ratio along each dimension

I calculated the resizing ratio for Potential FCS-CB 3:

Calculating Resizing Ratio Original F-CB Potential FCS-CB dimensions 3 Resizing Ratio (custom:original)
Length (cm) 23 19 0.826
Height (cm) 13 13 1
Depth (cm) 11 8 0.727
Cross-section shape triangle triangle
Volume (cubic cm) 1645 988 0.60

There are cases where you may choose to change only one dimension (e.g. shortening or lengthening a project) or two dimensions (eg changing the orientation from landscape to portrait).

A shorter, shallower customized SSE cosmetic bag with the same height as the original would meet my minimum volume requirements.

Same re-sizing ratio along all 3 dimensions

Aesthetically, I would prefer my customized cosmetic bag to be proportional smaller than the original (length, height and depth with the same ratio). I choose a resizing ratio of 0.83 from the above table and check that I meet my requirements for a target volume of between 935 cm3 and 1645 cm3. You can see from the below table that it didn’t and that I tried a few other resizing ratios.

Resizing Ratios versus Volumes Original F-CB (orange, grey & white) Ratio FCS-CB4: F-CB Potential Dimensions FCS-CB4 Ratio FCS-CB5: F-CB Potential Dimensions FCS-CB5 Ratio FCS-CB6: F-CB Potential Dimensions FCS-CB6
Length (cm) 23 0.83 19.1 0.9 20.7 0.87 20.0
Height (cm) 13 0.83 10.8 0.9 11.7 0.87 11.3
Depth (cm) 11 0.83 9.1 0.9 9.9 0.87 9.6
Volume (cubic cm) 1645 940 1240 1084
Assessment too small too big? just right

I like the dimensions resulting from the resizing ratio 0.87 the best (FCS-CB6). These dimensions (20 cm long by 11.3 cm high by 9.6 cm deep) result in a volume of 1084 cubic centimetres. This is 96 cubic centimetres. larger than my black cosmetic bag and that capacity would hold 96 millilitres of water. All of my travel toiletries would fit with room to spare.

Stay tuned for part 2 of 2 in this series on re-sizing PDF patterns.

Have you re-sized PDF patterns? If so, what method did you use? Comment below and/or Pin Me For Later.

Tanya

Sewn By Tanya Sewing Tutorial: Re-sizing PDF Patterns part 1

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.