Choose the pattern size to fit the chest. This gives a better fit throughout the entire body.
This is why:
1. When the pattern is chosen to fit the chest size:
The pattern size fits the woman’s bone size, her true body fit.
Less alterations are needed.
Many difficult alterations are eliminated.
The pattern will need fewer corrections.
Note: ALL patterns should be checked with a muslin fitting before they are used the first time.
2. When the pattern is chosen to fit the bust:
If full-busted half of the extra room needed to fit the bust is in the back of the garment.
If small-busted, the bust fit may be accurate, but the pattern will be too small.
Measure the bust to determine the cup size
The bust measurement printed on the pattern jacket fits an A cup.
The pattern REALLY fits is a B cup, two inches larger than the bust measurement on the pattern jacket.
The pattern’s bust measurement is four inches more, plus 1/2 inch for ease, than the chest measurement. The diagram below on the right shows how to determine the patterns’ true bust measurement.
If the bust is 4 inches larger than the chest measurement, the woman wears a B cup. The pattern’s bust area fits her. If the woman’s bust is 5 inches larger than her chest measurement the bust measurement needs to be increased 1/2 inch on either side of the front bodice pattern.
How the bust is measured:
Bra companies determine a woman’s bra size by first measuring the chest under the bust. They then add five inches to give the bra size. This size is for a C cup. If the bust measures the chest size plus 5 inches, the cup size is a C, the average cup size in each bra size. But if the bust measures the chest size plus 4 inches, the cup size is a B. If the bust measures the chest size plus 6 inches the cup size is a D.
Home sewing pattern companies use the same system, but traditionally draft their patterns with a B cup.
Cup Sizing Chart
Cup size nomenclature is related to bust circumference. The same cup size in the next largest bra or pattern size is given the previous letter. For example: The size C cup in a 34 bra is a size B cup in a 36 bra. The size B cup in a 36 bra is a size A cup in a 38 bra.
Once the pattern size is determined, decide how much additional bust darting needs to be inserted into the front bodice of the pattern.
If the woman is small busted, the bust darting may need to be reduced.
Also check the bust area. The bust area of home sewing patterns is often not drafted into the grade-rule’s position. Refer to Post 77: Moving the Bust Area for more information.
To increase the bust fit refer to the diagrams A and B on the left and right.
I’ve finished editing a book that addresses these and other fit issues. Included is how grade rules work and how to develop patterns and grading coordinates to grade patterns to fit. All that is needed is a ruler, tracing paper, and a pencil. I hope to have the book finished by the end of the year.
Grade rules are sets of complete body measurements, used to determine the fit through a range of sizes. If one knows how one’s body measurements differ from their best size in a grade rule, patterns from that grade rule can be graded to fit that person.
The book contains over 400 pages. More about that book and its series are at this link.
© Laurel Hoffmann, 2018.
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- 136: How to Use Directional Sewing November 22, 2020