In this section, we’ll look at how to grade between sizes on a garment with princess seams, which takes a slightly different approach to darted garments, although the underlying principles are the same.

Take your measurements and assess which sizes you need to grade between

Always retake your measurements before starting each project. Make sure you’re wearing the type of bra you’ll be most likely to wear with the garment and take your waist and hip measurements while both standing up and sitting down to make sure you have sufficient wearing ease in your garment.

Choose your size based on your standing measurements, then compare your seated measurements with the finished garment measurements to ensure that you have enough ease when seated.  If your sitting measurements are larger than the finished garment measurements, size up until your seated measurements are smaller than the finished garment measurements.

Let’s say you have standing measurements of 45″ (114 cm) at the full bust, 38″ (97 cm) at the waist and 52″ (132 cm) at the hip.

If you look at the body measurement chart, you’ll see your bust would fall in the 16 E/F, your waist would fall in the 18, and your hips would fall in the 22.

Body Measurements (in)

12 14 16 18 20 22 24 26 28 30 32
High Bust 37 39 41 43 45 47 49 51 53 55 57
Full Bust, C/D Cup 40 42 44 46 48 50 52 54 56 58 60
Full Bust, E/F Cup 41 43 45 47 49 51 53 55 57 59 61
Full Bust, G/H Cup 42 44 46 48 50 52 54 56 58 60 62
Waist 32 34 36 38 40 42 44 46 48 50 52
Hip 42 44 46 48 50 52 54 56 58 60 62

Body Measurements (cm)

12 14 16 18 20 22 24 26 28 30 32
High Bust 94 99 104 109 114 119 124 130 135 140 145
Full Bust, C/D Cup 102 107 112 117 122 127 132 137 142 147 152
Full Bust, E/F Cup 104 109 114 119 124 130 135 140 145 150 155
Full Bust, G/H Cup 107 112 117 122 127 132 137 142 147 152 157
Waist 81 86 91 97 102 107 112 117 122 127 132
Hip 107 112 117 122 127 132 137 142 147 152 157

Double check your seated measurements against the Finished Garment Measurement table.  Assuming your sitting waist is 40″ (102 cm) and your sitting hip is 55″ (140 cm), these measurements are less than those for the finished garment so you are ready to get started.

Finished Garment Measurements (in)

12 14 16 18 20 22 24 26 28 30 32
Full Bust: C/D cup 42 44 46 48 50 52 54 56 58 60 62
Full Bust: E/F cup 43 45 47 49 51 53 55 57 59 61 63
Full Bust: G/H cup 44 46 48 50 52 54 56 58 60 62 64
Waist 38 40 42 44 46 48 50 52 54 56 58
Hip 47 7/8 49 7/8 51 7/8 53 7/8 55 7/8 57 7/8 59 7/8 61 7/8 63 7/8 65 7/8 67 7/8

Finished Garment Measurements (cm)

12 14 16 18 20 22 24 26 28 30 32
Full Bust: C/D cup 107 112 117 122 127 132 137 142 147 152 157
Full Bust: E/F cup 109 114 119 124 130 135 140 145 150 155 160
Full Bust: G/H cup 112 117 122 127 132 137 142 147 152 157 163
Waist 97 102 107 112 117 122 127 132 137 142 147
Hip 122 127 132 137 142 147 152 157 162 167 172

Grading between sizes on princess seams

In order to retain the correct shaping on princess seam garments, and not change the lengths of the princess seams, there is a different approach to grading between sizes on princess seams. Instead of grading at each seam, we instead grade at the side seams. This maintains the princess seam shaping, while adding the extra room you need at the waist and/or hip.

As always, check the finished garment measurements before grading; it’s possible you can skip grading between sizes if the garment has sufficient ease.

Grading between sizes on a princess seamed top or shirt

Here is how you would grade between sizes on a princess seamed button-up shirt like the Harrison. Even though the Harrison has two princess seams, we are going to only grade at the side seam.

If you look at the difference in finished garment measurements in our example, the 16 has a finished waist of 42″ (107 cm) and the 18 has a finished waist of 44″ (112 cm), with a difference of 2″ (5 cm). We want to add this to our 16 at the waist. The simplest way to do this is to add 1/2″ (12 mm) to the side seam of the side front and side back pieces (2 front sides at 1/2″/12 mm + 2 back sides at 1/2″/12 mm = 2”/5 cm). Add this width at the waist point of the piece.


Next, let’s look at the hip measurements. Again, starting at the 16, there’s a finished measurement of 51 7/8” (132 cm). The 22 (which fits our body measurement) has a finished measurement of 57 7/8″ (147 cm). This is a difference of 6” (15 cm). At the hip point of the side front and side back pieces, we’re going to add 1 1/2” (3.8 cm). This will give us the additional ease we need around the hips.

Finally, we’ll connect the graded points using a curved line, matching the front and back side seam.


The remainder of the pieces can be cut at a straight size 16. Pay careful attention to the size lines, keeping an eye on the way the pieces are stacked on the side back. Unless you need extra length, the pieces can all be cut as the length of the 16. Make sure your seams have steady curves and the ease is added where you need it vertically and definitely make a muslin to test these changes.

Grading between sizes on a princess seamed skirt

The process for a skirt is essentially the same. Begin by identifying which pattern pieces are on the side seam. For most skirts, there will be a front and back piece that both have a side seam. However, in this example we are using the Osgood Skirt which has an asymmetrical front, which means we need to alter three pieces: the Side Front Left, Side Front Right, and Side Back.

Note: the Osgood has a lot of ease at the hip so in most cases you probably wouldn’t need to grade up at the hip as the finished garment measurements would give you enough room—but if you do, this is how you’d do it.

Taking the same measurements as before of a 38″ (97 cm) waist and 52″ (132 cm) hip, this would be an 18 waist and 22 hip. In this case, to grade form a size 18 with a body measurement of 48″ (122 cm) to a 52″ (132 cm) hip, we’d need to add 4″ (10 cm) to the hip in total (note as above, in reality for this specific pattern, you wouldn’t need to grade due to the ease). To add a total of 4″ (10 cm) to the hip, we’d need to add 1″ (2.5 cm) to the side seam of the front pieces, and 1″ (2.5 cm) to the back.

To do that, measure out 1″ (2.5 cm) from the hip notch of the 18, and then simply join up to the 18 at the waist with a gentle curve. There are two options below this point: you can carry on with the wider width all the way down (which will create a wider hem), or you can gently curve the line back in—however, if you do this, you must ensure the curve of the line and the length of the line is the same on all the altered pieces.

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