Basic bikini WELL’S BAY is drafted for a sewing B cup and is most suitable for smaller busts, but you can make it work for your C or D cup with a simple adjustment. If your full bust measurement is more that 5 cm (2”) wider than your upper bust, you will require a Full Bust Adjustment with this pattern.
In sewing, cup sizes are measured based on the difference between your upper bust and full bust measurements as follows:
• A cup = 2.5 cm (1") difference
• B cup = 5 cm (2") difference
• C cup = 7.5 cm (3") difference
• D cup = 10 cm (4") difference
To choose the correct pattern size to start with, measure your upper bust and add 5 cm (or 2"). For example, if your upper bust measures 83 cm (approx. 32½”), you will use the size 4 pattern piece (front and back) because 83 cm + 5 cm = 88 cm (or 32½” + 2” = 34½”)
However, perhaps your full bust actually measures 93 cm (approx. 36½"). You will calculate the required adjustment for the pattern piece like this:
(actual full bust - pattern full bust) / 2 = required adjustment
• 93 - 88 = 5
• because the pattern piece is only half the bust, you will need to divide by 2, so: 5 / 2 = 2.5 cm
• 36¾” - 34¾” = 2”
• because the pattern piece is only half the bust, you will need to divide by 2, so: 2” / 2 = 1”
Once you've determined the required adjustment amount, you can get started. For this example, we will continue with a 2.5 cm (1") adjustment (so, a sewing D cup).
1. Draw “slash and spread” lines on your pattern piece, as indicated in the photo. Note that the line through the center of the dart extends 1.5 cm (5/8”) past the dart apex (which should be your bust point).
2. Cut lines 1 and 2 through the center of the dart up to, but not through, the seam allowance at the upper side seam.
3. Cut the line from the side seam, almost – but not all the way(!) – to the point 1.5 cm (5/8”) above the apex.
4. Cut the line from the center fold to the vertical line through the dart.
5. Secure the upper portion of the pattern piece and, keeping the vertical and horizontal lines parallel, gently shift the lower piece until the vertical gap is equal to your required adjustment (ie. 2.5 cm or 1” for our example).
6. Now, again keeping the vertical and horizontal lines parallel, realign the legs of the dart until they are horizontally even.
7. Either place scrap paper under your slashed-and-spread pattern piece or grab a piece of pattern paper to retrace. Draw the upper, lower and center fold line. Join the outer points of the upper and lower lines to recreate the side seam. Measure up 3.5 cm (approx. 1 1/3”) along the outer seam and place the double notch.
Use the original dart apex and redraw the dart. Or, place the pattern piece over your bust to find the best placement for your dart apex. This should be approximately
8. Lastly, you will need to adjust the upper curve on the back pattern piece to match your new front piece. Do this by simply extending the line at the side seam as needed, then joining the top of that line with the point at which the back turns into a strap. Place the shoulder strap notch on the adjusted back pattern piece at the same distance from the seam as the original.
You've done it!