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Add a Bust Dart

This adjustment for a full bust flatters the entire silhouette
Threads magazine - 142 – April/May 2009

For the last couple of seasons, pattern companies have featured wonderful, youthful jackets—but if they don’t have bust darts, you may shy away from them because you know bust darts can be a girl’s best friend. When placed properly, a couple of bust darts make your bustline look perfect and flatter your waistline, too. Fortunately, it is not difficult to add bust darts to a pattern.

Once you’ve determined your correct bra size, you can follow a simple formula to add bust darts of the right size to your patterns. I guarantee you’ll end up with a better fit than you’ll ever find in ready-to-wear.

Learning to fit the bust size

This is the before learning to fit the bust size

Darts for the perfect fit. The jacket on the left has no bust darts. A dart tries to form under the arm, the center front hem flips out, and fabric strains across the bust. When you add a dart to the same pattern, the jacket is smoother and fits better, as shown at right.

Add bust darts for the perfect fit. When you add a bust dart to the same pattern, the jacket is smoother and fits better.

Fit the bra with the proper measurements

Most pattern companies design bodice patterns to fit a B cup. That’s great if that’s your correct size, but I’ve discovered that many women with bust-fitting issues often don’t know their correct bra size. It takes three measurements to determine your bra size.

Put on your best-fitting bra to measure the circumference under your bust. Keep the tape measure snug. To this measurement, add either 4 or 5 inches to get an even number. This total is your bra-band size.

Next, measure the circumference above your bust. This measurement is taken high under your arms. It is your chest—excluding your bust—and is called the “high bust” measurement.

Then, measure around your full bust. Make sure the tape measure is parallel to the floor all around the body and is positioned over the fullest part of your bust.

Subtract the high-bust measurement from the full-bust measurement. The difference determines your cup size.


Bra cup size

Less than 1 inch

1 inch A
2 inch B
3 inch C
4 inch  D
5 inch  DD or E
6 inch DDD, EE or F

Measure the new you

Buy a new bra in the size determined. Then, while wearing your new bra, check the band and shoulder straps. The band should be horizontal around the circumference of your body, and the straps should be secure so they don’t fall off your shoulders. Measure from the shoulder to the waist over the bust point. Adjust your straps so the apex of your bust is above the halfway point. The higher your bust, the more youthful (and thinner) your figure appears.

1. Bust depth. Stand in front of a mirror, and measure from the shoulder seamline directly below your ear to your bust point.

2. Bust width. Next, measure the distance between your bust points. Then divide this measurement in half ; this is the distance of your bust points from the pattern’s center front.

Mark the pattern

Map out the “new you” measurements on the front pattern. This alteration adds vertical and horizontal fabric to accommodate a fuller bust.

1. Transfer your measurements. From the intersection of the neckline and shoulder seam down the front of the pattern (parallel to the grainline), measure the bust-depth distance you measured, and make a dot. This is not your bust point, it only indicates bust-point depth. The bust-point dot is placed in step 3.

2. Draw a horizontal line through the dot. Draw a line perpendicular to the grainline from the center-front line through the dot to the side seam.

Draw a horizontal line through the dot.

3. Mark the bust point. Starting at the center-front line, measure the distance of along the horizontal line, and draw a large dot. This dot is the correct bust point.

4. Add a diagonal line. Draw a second line from the bust point to the notch in the armscye. If there is no notch, divide the armhole curve into thirds, and draw the line to the lower third of the armhole.

5. Add a vertical line. Draw a third line parallel to the grainline from the bust point to the bottom of the garment.

Add a diagonal line

6. Slash to the bust point. Cut the pattern along the horizontal line from the side seam to—but not through—the bust point. Slide a piece of tissue under the pattern.

7. Cut the vertical line. Cut from the bottom of the garment front to the bust-point dot. Continue to cut to the armscye seamline, and leave a hinge. When the pattern is spread to accommodate the bust, the seamline at the armhole stays the same length. Cut the tissue at this same point from the edge of the armhole to the seamline; keep the hinge.

8. Carefully spread the vertical line. Slide the pattern tissue in the direction of the arrow, keeping the vertical slash lines parallel. Spread the pattern according to your cup size, using the “Cup Chart” below. Add this amount to the width of the vertical gap—not the width of the “dart” section. The bust-dart section will open as the pattern is spread. Although it looks as if the dart is forming, the wedge-shaped area is not quite right yet.

Cut the vertical lineCup Chart

9. Cut along the horizontal bustline. Cut from the bust point to the center-front line. Slide the pattern section down until the two pattern hemlines align. Tape the vertical cut edges to the tissue underneath. Draw a center-front line to connect the upper and lower portion of the pattern.

Cut along the horizontal bustline

10. Find the true dart. The wedge shape that has formed is not the true dart. To find the true dart, draw a line from the bust point to the side seam in the center of the wedge opening. This is the center foldline of the dart.

11. Mark according to size. If you are making a size smaller than 16, mark a dot on the foldline 1 inch away from your original bust-point dot. If you are using a size 16 or larger, place the dot 2 to 212 inches away from the bust-point dot. The dart point should never end exactly at the bust point. 

Mark according to size

12. Draw the dart legs. Mark a line from the top and bottom edges of the wedge shape to the new dart-point dot.

13. Fold the center dart line, and bring the two legs together. Then fold the dart up, as if pressing it into position. When you press the side darts up for a full bust, it makes the bustline look higher. Cut off the excess paper along the side seam. When the paper dart is released, a small divot of paper will form along the side seam. This will be needed when sewing your garment.

Fold the center dart line, and bring the two legs together.

 Add fabric when adding a dart. When you add a bust dart to a pattern, the width and length of the front need to increase to accommodate the larger cup size.
Add fabric when adding a dart. When you add a bust dart to a pattern, the width and length of the front need to increase to accommodate the larger cup size.


Previous: Fitting a Curvy Figure Next: Focus on the Waist to Fit Pants


  1. user-2755931 | | #1

    This article is missing the cup chart mentioned in Step 8. This would give the amount you need to spread the pattern at the vertical slash. I believe for a C cup the amount is 1/2”.

  2. user-54312 | | #2

    Yes, this doesn't seem to work unless you have the chart. Please add

  3. carolfresia | | #3

    Thank you for pointing out that the chart didn't get uploaded to the post. We'll take care of it shortly.
    Carol Fresia
    Threads Senior Technical Editor

    1. user-54312 | | #4

      Thank you!

  4. user-54312 | | #5

    just now putting this to use, but step 3 doesn't make sense. Measure the distance of what?

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