My vintage sewing pattern collection started when I was about 18. The patterns opened up a world of fashion and self-expression for me just as I was exploring my aesthetic as a young woman, and so I committed to learning to sew.

Unlike modern sewing patterns, the vintage ones usually only ever came in single sizes, so I would spend hours trawling through vintage sewing pattern sellers online, looking for the ones that matched my measurements.

At the time, the thought of altering a pattern to fit me better seemed so far out of my league; it never occurred to me that I might be able to manually grade the pattern up or down a whole size! It pains me now to think of all the breathtakingly beautiful patterns I missed out on just because they weren’t my size.

Nowadays, most patterns come multisized, but what if your measurements fall outside of the given sizing charts? The good news is that, whether your measurements are not represented by the pattern you want to sew, or you have some vintage gems that you need to size up or down, manually grading a pattern is totally doable.

I’m going to show you what I feel to be the most reliable and efficient way to grade a pattern at home. This technique uses the slash and spread/ overlap method – we’ll be cutting right through the pattern horizontally and vertically, and spreading it out (or overlapping it) thereby increasing (or decreasing) the pattern while keeping it in proportion.

10 FREE Jersey Dress Patterns

PATTERN GRADING EXPLAINED

So what is pattern grading?

Unlike pattern alteration – where you hone in on specific areas of a pattern that don’t fit you well, like if the apex is too high, or you have some gaping in the neckline for example – pattern grading is the proportional increase or decrease of a pattern’s overall size. If you suspect you may need to alter the fit of the pattern as well as grading the size, it’s important to grade the pattern first, before you sew a toile and diagnose fit issues.

You’ll notice when we get to grading that the bodice pattern increases/decreases by different amounts at different points. This is because as the body goes up/down a size, the extra surface area is distributed more at certain parts of the body, and less at others. The most significant increase/decrease happens near the side seams, but there is also a slight increase either side of the centre front/centre back, at the shoulder, and down the length of the pattern piece. The increase/decrease in length is not because it is assumed that as people go up or down a size they are taller or shorter, it’s simply because the fabric will have a longer distance to travel from neckline to hem on a larger size, and less distance to travel on a smaller size.

And finally, in order to maintain the proportions of a pattern, it is not recommended that you manually grade up or down more than about four sizes (up to about 8”). The proportions can become distorted and you’ll likely end up with a whole bunch of unnecessary and unwanted fit issues!

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SLASH & SPREAD METHOD

For this tutorial, I am going to show you how to grade a bodice front (the same applies to the bodice back), a sleeve and a straight skirt pattern. We will be increasing the pattern by about one size and going up by a total of 2” all around. The lower end of a sizing chart, one ‘size’ usually represents a difference of 1”, and as you go up through the sizing chart this increment between sizes jumps to 2” and then 3”, so I’d suggest you think about grading in terms of measurements as opposed to 'sizes'.

Grading a bodice

Start by tracing off your bodice front. We’re going to start by drawing the slash lines:

Vertical line from the neckline to waist, about an inch in from the centre front (CF).
Vertical line from the shoulder seam to waist, trying to skim the outside of the waist dart.
Vertical line from armscye to waist, about an inch in from the side seam.
Horizontal line just before you get to the cradle of the armscye out to the CF.
Horizontal line a couple of inches up from the waist, where you would usually lengthen or shorten your bodice.

Lay your pattern piece out on a piece of plain pattern paper, and cut through your slash lines, taking care not to jumble the pieces up! Start by taping down the CF neckline piece (A). From here we will be spreading out the pattern, starting by focusing on the vertical lines.

The maths bit: If we want a total increase of 2”, that will be an increase of ½” on this bodice front, which represents a quarter of the total bodice (two CFs, two CBs). As I mentioned before, the area closest to the side seam is where the biggest increase will be, with smaller increases at the shoulder and CF. We’re going to increase the two vertical lines at the shoulder and CF by 1⁄8” each, and the vertical line closest to the side seam by ¼”. If you need to increase or decrease by more, use that same formula - half of the measurement (in this case ½” – which is in turn a quarter of the total measurement) at the side seam, and a quarter each at the shoulder and CF.

Moving across 1⁄8” from Piece A, tape down Piece B, keeping the horizontal slash line flush. Tape down Piece C in the same way, 1⁄8” across from Piece B.

When we get to the next row, we need to consider the increase at the horizontal lines. For this grade, we’ll be increasing the total bodice length by ¼”. This will need to increase to ½” if you are grading more than 4” total. Piece D will need to be taped down flush with the CF line, and 1⁄8” down from Piece A.

And so it continues: 1⁄8” increase between pieces D, E and F; ¼” increase between F and G. Another 1⁄8” increase at the second horizontal line and pieces H, I, J and K follow as the previous row.

At this point do not worry about the darts, but keep the dart leg notches intact at the side and waist seams. The darts will not change size – dart width, length and angle all stay the same, so once your newly graded pattern has been traced off, the original darts can just go back to their notches. When all the pieces of your pattern are securely taped down, trace it off, trueing and blending out the lines.

Replace the darts, cut it out and there you have it!

Grading a sleeve

To grade your sleeve to match the bodice, mark the following slash lines:

Horizontally across the sleeve cap, just above where the sleeve front and back notches usually sit.
Horizontally across the bicep, about an inch down from the underarm.
Vertically from the armscye to the bicep line, about an inch in from the underarm seam – each side.
Vertically from the bicep line to the cuff, in the centre of the sleeve.

Cut and assemble the pieces on some paper as you did for the bodice. Going by the same grade as the bodice, you will need to spread your sleeve by the following amounts:

1⁄8” between pieces A and C (corresponding to the first horizontal increase in the bodice).
¼” between pieces B and C, and between pieces C and D (corresponding to the increases at the bodice side seams).
1⁄8” at the horizontal bicep line (adding a little extra length to go over a larger bicep).
½” at the vertical line between pieces E and F (corresponding to the total increase of the width of the sleeve).

Grading a skirt

To grade your skirt to match the bodice, mark the following slash lines:

Vertical line from the waist to hem, about an inch in from the centre front (CF).
Vertical line from the waist to hem, on the other side of the waist dart.
Vertically from the waist to hem, about an inch in from the side seam.
Horizontal line at about hip height, just below the waist dart.
Horizontal line further down the skirt.

Cut and assemble the pieces on somepaper as you did for the bodice and sleeve.

Going by the same grade as the bodice, you will need to spread your skirt by the following amounts:

1⁄8” between pieces A, B and C.
¼” between pieces C and D.
1⁄8” at both horizontal bicep lines.
1⁄8” between pieces E, F and G.
¼” between pieces G and H.
1⁄8” between pieces I, J and K.
¼” between pieces K and L.

Once you’ve altered the size of your bodice, sleeve and skirt, you’ll need to adjust any facing or lining pieces to match. Always sew up a quick toile after you’ve graded your pattern to check the new sizing and see if you need further and more specific fit alterations – most of us do!

Masterclass: How to Grade Up A Dressmaking Pattern