Pattern Grading Calculator
How far a pattern edge moves per size.
Calculate how much to move a pattern edge when grading between sizes, accounting for whether the piece is a quarter, half or full of the garment.
Negative to grade down.
Move the pattern edge by
0.50"
2.00" around the body
Applying the full body change to a quarter pattern grades four sizes rather than one — the commonest grading error and one that produces a garment that looks plausibly drafted and fits nobody. Lengths grade far less than girths, usually about a quarter as much.
How the Pattern Grading Calculator works
Grading moves a pattern between sizes, and the arithmetic trips people because a pattern piece is not the garment. A size step of one inch is a change around the body; a front bodice cut on the fold is a quarter of that circumference, so its edge moves by only a quarter of an inch. Applying the full inch to the piece grades four sizes rather than one.
Also known as: pattern size grading calculator · grade a pattern calculator
Why a one inch size step moves a quarter inch
A size step is a change around the body: in misses sizing, about an inch at the bust, waist and hip. A pattern piece covers a fraction of that circumference — a front cut on the fold is a quarter of the body, a full front is a half.
So the edge of a quarter-pattern moves by a quarter of the body change. Grading up one size on such a piece means moving the side seam out by a quarter inch, not an inch. Applying the full inch grades four sizes.
Lengths grade far less than girths, usually about a quarter of the girth change per size, because people do not get proportionally taller as they get wider. Grading length by the same amount as width is the second commonest error.
A worked example
Grading a bodice front, cut on the fold, up two sizes at an inch a size. The body change is two inches; the piece is a quarter of the body; so the side seam moves out by half an inch.
The length grade over the same two sizes is about half an inch total, spread between the armhole depth and the waist length rather than added at one point. A pattern graded correctly for width and wrongly for length produces armholes that are the right size and in the wrong place.
Where the answer misleads
Grading is linear and bodies are not. Armholes, necklines and shoulder slopes do not scale with girth, which is why a professionally graded size run adjusts them separately rather than moving every edge by the same proportion. Beyond one or two sizes, a linear grade drifts noticeably.
It also assumes the change is distributed evenly around the body, and real grading rules distribute it unevenly — more at the side seam than the centre front, for instance. This gives the total movement, not where to put it.
Where the pattern already provides the size you need, use it. Grading is for sizes outside the range, or for grading between two provided lines when you are one size at the bust and another at the hip.
Frequently asked questions
How much does a pattern change per size?
In misses sizing, about an inch around the body at bust, waist and hip. On a quarter pattern piece that is a quarter inch of movement; on a half piece, half an inch. Lengths grade far less, usually a quarter of the girth change.
Why is my graded pattern too big?
Almost always because the full body change was applied to the pattern piece. If you moved a quarter-pattern edge by a full inch you graded four sizes, not one — the piece covers a quarter of the circumference and the change is shared four times.
How many sizes can I safely grade?
One or two either way for most patterns. Beyond that the proportions stop being right — armholes, necklines and shoulder slopes do not scale linearly with girth, and a properly graded size run adjusts them separately.
Should I grade or use a bigger pattern?
Use the drafted size where one exists. Grading is for sizes outside the range, or for the common case of being one size at the bust and another at the hip, where you grade between two lines the pattern already provides.