Sewing Pattern Fitting and Alteration

Sewing pattern fitting and alteration. Two steps for sewing clothes that flatter your body shape and make you look gorgeous.

There’s nothing better than having clothes exactly the way you want them. Not too long, too short, too tight or too lose.

You know your body better than anyone else and know how YOUR clothes should fit. This my dear friend, will allow you to sew the best clothes for yourself.

Commercial patterns come in standard measurements. There are few people who fall perfectly into any one of the sizes.

By making a few pattern alterations, you’ll be able to mold standard patterns to your body like a second skin. You deserve to look gorgeous with the clothes you make!

Follow these steps for sewing pattern fitting and get it right every time.

Sewing Pattern Fitting

1. Select a size

Select your pattern size and determine differences between your measurements and the pattern’s.

2. Divide Measurement Difference by 4

You already know the difference between your measurement and the pattern’s but this is for the whole circumference.

In clothing you usually draw the patterns for either 1/2 or 1/4 of the body. To do the pattern fitting, divide the difference you got by 4 to know exactly how much you need to add or subtract on each part.

Sewing Pattern Fitting and Alteration

New Look 6022 Dress Patterns- Front and Back

On Patterns that are only half of the whole piece (like my front and back patterns for the dress I’m using in these tutorials) and that you’ll cut with folded fabric, add only 1/4 of the difference to the outer edge.

On patterns that are symmetric and that you’ll be cutting without folding fabric, add 1/4 of the difference to each side.

For my dress patterns, I need to add 1 1/2″ to the waist. I divided this measurement by 4 and got 3/8″.

3. Iron the Patterns

Envelope and magazine patterns are always wrinkled. Carefully straighten them out with the help of an iron.

4. Make a Copy of Your Original Pattern

The pattern should come with a key that tells you how to identify each size. They usually come in different colors or line textures. Locate all the pattern pieces for your size.

Sewing Pattern Fitting and Alteration

Many people cut the pattern out. I trace it on another paper so I can do the necessary pattern fitting and keep the original safe. If I mess up or lose the pattern I can easily make another copy.

Place a thin see through paper on top of the pattern and pin it so it doesn’t move. Trace each one of your pieces using a pencil so you can easily erase. Transfer all the pattern’s symbols, names, piece numbers and any additional information it has. You’ll need it for cutting and sewing!

Sewing Pattern Fitting and Alteration

There are many good papers for this, but it all depends on personal preference and budget. My favorite is swedish tracing paper. It’s heavier than the tissue used by pattern companies but it’s light enough so I can see through and easily trace my new pattern.

It’s resistant enough so I can use the pattern several times and works well to make muslims for pattern fitting.

5. Mark Seam Allowances and Hem Lines

Sewing Pattern Fitting and Alteration

Mark seam allowances and hem lines on all the pattern pieces you just traced. If the pattern instructions specify that the seam allowances ARE included, mark them towards the inside.

Do the same with the hem lines. This will allow you to see where the actual pattern is.

If they are NOT included you won’t need to do this until later because you already have the real pattern size.

6. Add or Subtract Inches Where Needed

Sewing Pattern Fitting and Alteration

On the pattern, you’ll see structural lines that indicate where the bust waist and hips are. This is where you’ll be doing the pattern fitting by either shortening or lengthening.

In the places that you got positive numbers you’ll need to enlarge the pattern. Mark the difference along the structural line towards the outside. If you have a negative number mark towards the inside along the line.

Measure from the pattern’s real edge (without the seam allowance). Any change you do on the front, you must also do on the back. Use a colored pencil to easily see the changes.

7. Trace New Edge

You’re almost done! All you have to do now is retrace the pattern’s edge. You know where you need to make the pattern larger. We will use the original pattern for tracing the new line.

Sewing Pattern Fitting and Alteration
  1. Place the copy you made over the original pattern. Fix a point with the help of a pin. I’ll fix the armscye’s base because this is the starting point of the line I’m going to change. Move the top pattern until the modified waistline (marked in red) is aligned with the original edge and trace.
  2. Do the same for the bottom part of the pattern, but fix it on the bottom corner.
  3. This would be the new pattern’s edge

Note:Only change the parts of the pattern where the measurements are different from yours. Everything else should remain the same.

You can modify sleeves, necklines and any other part of the pattern with the same method. Just compare your measurements to the pattern’s to see where they are different. Here’s an example on how to change a sleeve.

Let’s say that you took your upper arm measurement and you got 9″ all the way around. If you measure the sleeve’s bottom edge, you get 13″. There is a 4″ difference between them.

Sleeves need to be loose so you can move your arm but 4″ is too much. You decide to make the sleeve 1 1/2″ smaller so its final measurement is 11 1/2″.

Divide 1 1/2″ by two and you get 3/4″. This is what you need to subtract from each side of the sleeve’s bottom edge, everything else would remain the same. Your new pattern would be marked by the orange line.

Sewing Pattern Fitting and Alteration

8. Add New Seam Allowances

Once you have the edge redone, you need to add the new seam allowances. Check the pattern’s instructions to see how much you should use. Add it on the pattern’s new line (marked in red on figure 3, from the first drawing in step 7), not the original one.

If your pattern included seam allowances, you’ll only need to add it to the modified parts. If it didn’t include it, add it all the way around. You’re done with the pattern fitting.

Cut your pieces and they’re ready to be sewn! These are the basic steps for fitting a commercial sewing pattern. If you’d like to learn more about it, I suggest you try this online class.

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