Diamonds are a Sewist’s Best Friend

The best part about making your own clothes is having the ability to customize an existing pattern to your own style and fit preferences. Personally, I like a slightly flared skirt or dress more than a very boxy design on myself, and often make small pattern changes to achieve this. One technique for achieving a slightly more shaped fit is to add diamond darts. Diamond darts may be added at the back or the front (or both) and will slightly reduce the width of the waist without reducing the diameter of the hip. The amount you reduce is up to you, but there are some guidelines you can follow to help achieve an excellent fit and desired silhouette in your garment.

What is a dart?

Darts are used to remove excess fabric from a design to create a more fitted effect. The amount that is folded or pinched out of the fabric is called the “take-up”. Darts are commonly used in woven designs on front bodices to taper the fit from the bust to the waist, back bodices to taper the fit from shoulder to waist, and the shoulder (on a back bodice) to taper the fit between shoulder blade and shoulder seam. They are also used on pants and skirts at the front and back to taper the fit from hip to waist. (Note: darts are not often used on knit garment designs, because knits allow stretch and do not always need the shaping that darts provide).

What is a diamond dart?

A diamond dart (sometimes called a fish-eye dart) is used on garments with no waist seam. It is essentially a combination of a bodice dart and a hip dart and is sewn in a single step. When garments have bodice and hip darts with a waist seam, they can be fitted very close to the body since the waist seam provides an opportunity for additional shaping. A dress or tunic with diamond darts will not achieve the same close fit without a waist seam, but the diamond dart can provide some shaping if a very boxy silhouette is not desired.

Front, back, or both?

I often only add diamond darts to the back of dresses or shirts to avoid disrupting the clean lines of the front of the garment. However, diamond darts are commonly used on the front of garments, so you should add yours according to your own preference.

To check if diamond darts are suitable for your garment, consider the following:

1. No waist seam
   Diamond darts are added to garments that do not have a waist seam. If you have a waist seam, you will want to adjust the dart take-up on the bodice and the skirt/pant separately (not covered in this tutorial, but you could adapt the steps presented here). This tutorial will feature the V-Neck Dress, which does not have a waist seam. I have personally added diamond darts to my Cap Sleeve Dresses, Oversized Shirts, and an Elastic Tie Sweater that I lengthened to a dress.
   
   
2. Add for shape, not for size
   A diamond dart is meant to add some contouring to the garment, not to reduce the garment overall if it is too big. Your garment should be cut in the desired size for your body – then you can add diamond darts to play with the silhouette.

You can add your diamond dart to your pattern before sewing (if you know in advance how much you’d like to shape the garment), or you can play with the finished garment and sew the darts in after it’s made (then just transfer the markings to your paper pattern for future reference). I’ll demonstrate both approaches below.

A note about how much excess fabric a diamond dart can remove:

It is recommended to make the width of the dart at the waist (the take-up) approximately 2.5cm – 5cm (1″ – 2”) (for each dart). You can adjust this a little bit, according to your preference – it’s your garment after all – but keep in mind that more width or dart take-up may result in drag lines (the fabric will be pulling too tightly due to too much tension at the waist). Remember, the goal is not to make a tight fit, but to add a little contour and shaping. If in doubt, start with a small width and increase as needed. In practice, I have used wider darts with success, but the success depends on the weight of the fabric, the shaping that already exists in the garment (e.g. at the side seams), and the looseness of the garment overall.

Adding diamond darts to a pattern

FRONT

1. Diamond darts on the front should align vertically with the bust point, but should not be sewn all the way up to the bust point (BP). Start by lightly drawing a vertical guideline that is perpendicular to your centre front (CF) and extends from BP to hip

2. Mark a point on the line 1.25cm – 2.5cm (1/2″ – 1”) below the BP (the smaller measurement for a smaller bust, the larger measurement for a larger bust)

3. Mark a point on the line at the waist

4. Mark a point on the line approximately 5cm (2”) above the hip

5. Mark the width of the dart along the waist, centred over the vertical guideline

6. Connect the dots to form a diamond shape.

BACK

1. Diamond darts on the back should be positioned vertically, approximately 10cm (4”) from the centre back (CB). On the waistline, mark a point 10cm (4”) from CB.

2. Draw a vertical guideline that passes through the 10cm (4”) mark. The guideline must be perpendicular to CB (if CB is curved, the guideline should be perpendicular to the grain line) and extends from lower armscye (underarm) height to hip.

3. Mark a point on the line 1.25cm (1/2”) below the lower armscye (underarm) height. If your pattern uses a grown-on sleeve, estimate the position of the lower armhole based on how the back bodice curves into the lower edge of the sleeve.

4. Mark a point on the line 5cm (2”) above the hip

5. Mark the width of the dart along the waist, centred over the vertical guideline

6. Connect the dots to form a diamond shape

Adding diamond darts to a finished garment

1. Put the garment on your body. You may choose to put it on inside-out so that you are pinning and marking on the inside of the garment for the next steps

2. Identify the waist, hip, and upper dart end position

The garment waistline according to the pattern may not align with your natural waist, so identify the waistline based on your own body and preference. Remember, the waist is roughly in the middle of the dart, lengthwise, and will be where you will be reducing the most fabric from the garment. You can mark the waist with chalk, pins, or a basted thread (or just eyeball it for approximate positioning)

The hip line should be at the widest part around your hip/bum. Mark the hip line with chalk or a pin

The approximate upper dart end will align with the lower armscye (underarm) height (easiest to mark this before you put the garment on)

3. Approximately 10cm (4”) from the CB, along the waist, pinch some fabric from the garment and pin. This step is the same for front and back darts. Pinch fabric and pin in place until you achieve your desired shaping at the waist. Remember, diamond darts alone are not ideal for providing a “tight” fit, so you should aim to have a good amount of breathing room and ease. Be sure to insert the pins at the outer edges of the pinch points along the waist to mimic how your future stitches will hold the fabric together in a seam. Do this for both dart positions on the back (and the front, if creating front darts). It is helpful if you have a friend to assist, but it is not necessary. It does not need to be perfect at this stage – you can balance the dart width later so that it is equal

4. If creating front darts, also mark your bust point with chalk or pins. (This tutorial will only demonstrate the back dart but the instructions for front darts are provided)

5. Take the garment off and measure the full dart width at the waist for both darts (laying flat). Make note of the average measurement. For example, my left dart measured 3.25cm (1-1/4”) wide, and my right dart measured 2cm (3/4”) wide. So the average dart width will be 2.5cm (1”)

6. Next, calculate the average position of the back darts along the waist, measuring from the centre of the dart width to the CB. My left dart was 12.75 (5”) from CB and my right dart was 10cm (4”) from CB. This means the average position is 11.5cm (4.5”) from CB to centre of my dart width. Mark the position in chalk along the waist. For front diamond darts, reposition the darts to align vertically under the bust point

7. Mark the dart points:

Mark the dart width measurement that you recorded in Step 5 at the waist, centred across the dart position you marked in Step 6

Mark the top of the dart:

For front darts, the top of the dart will be 1.25cm to 2.5cm (1/2” to 1”) below bust point (use the larger number if you have a larger bust – and you may even wish to lower another 1.25cm (1/2″) after you test the fit).

For back darts, the top of the dart will be approximately 1.25cm (1/2″) below the lower armhole position

Mark the bottom of the dart:

For front darts and back darts, the bottom will be approximately 5cm (2”) above the hip line. You can reposition this higher or lower after you test the fit.

8. If you wish, draw the diamond dart lines with chalk or disappearing ink

9. Sew the darts closed. If you are unsure about the positioning and length of the dart, you may choose to use a basting stitch and test the fit before using a smaller stitch. Once you have confirmed the position and fit of the darts, fold the fabric so that the right sides are together, being mindful to match the dart points at the waist. Stitch from the top of the dart, carefully backstitching – you can reduce your stitch length for 10-15 stitches to help secure the thread. Then return to regular stitch length and stitch along the remaining length of the dart. Reduce your stitch length again as you approach the lower point of the dart and continue stitching right off the fabric to create a 3.75cm – 5cm (1-1/2″-2”) thread tail. The tail can be left as-is, or you can tie the ends together or weave them back into the seam

Happy sewing!