The upper back is a frequent source of fit problems, and two distinct adjustments handle most of them. A rounded back needs extra length to travel over a curved upper spine, while a broad back needs extra width to span shoulders wider than the pattern allows. They are often confused, but the remedies are different.
Getting them right matters because a restricted upper back is uncomfortable as well as unsightly, pulling every time the wearer reaches forward. This article separates the two problems and shows how to add exactly the right dimension in each case.
Telling a rounded back from a broad back
A rounded back shows as horizontal drag lines and strain below the back neck, with the garment pulling up at the center back when the wearer bends forward. It is a length problem: the fabric cannot reach over the curved upper spine.
A broad back shows as tightness and horizontal pulling straight across the shoulder blades, with the armholes cutting in and restricting forward reach. It is a width problem across the back, independent of the length issue.
The rounded back adjustment
- 1.Draw a horizontal slash line across the back from center back to the armhole, at the level of the shoulder blades.
- 2.Slash from the center back to, but not through, the armhole.
- 3.Spread the opening to add length at the center back, tapering to nothing at the armhole.
- 4.The center back seam lengthens; add a small dart or ease to absorb the extra width created at the neck.
- 5.True the center back and neckline as smooth curves.
Pro tip
The extra length from a rounded back adjustment often creates surplus at the neckline. Take it up in a small back neck dart or ease it into the neckline rather than leaving it to gape.
The broad back adjustment
To add width, slash the back pattern vertically from the shoulder down through the armhole area and spread it to add the required width across the back. This widens the back without lengthening it, which is exactly what broad shoulders need.
Because the spread crosses the armhole, the back armhole becomes slightly larger. Keep the change modest, or re-true the armhole and check it still matches the sleeve after adjusting.
Protecting the armhole and shoulder
- Slash up to, not through, the armhole point when adding length, so the armhole shape is preserved.
- Re-measure the armhole after a broad back spread and walk it against the sleeve cap.
- Keep the shoulder seam length matched between front and back after either change.
- Adjust the sleeve cap ease if the armhole circumference has grown noticeably.
When both adjustments are needed
Many people need both a rounded and a broad back correction, since a curved upper back and wide shoulders often occur together. Make them as two separate slashes, one horizontal for length and one vertical for width, rather than trying to solve both with a single cut.
Doing them separately keeps each dimension under control and makes it obvious how much of each you have added, which is important when you re-check the armhole afterward.
Balancing with the front
Adding length or width to the back changes how it relates to the front at the shoulder and side seams. After either adjustment, walk the shoulder and side seams against the front pieces and correct any mismatch, so the pieces still assemble cleanly and the garment hangs in balance.
Frequently asked questions
How do I tell a rounded back from a broad back?
A rounded back pulls and strains below the back neck and is a length problem. A broad back is tight straight across the shoulder blades with armholes cutting in, and is a width problem. Look at where the strain sits.
Does a broad back adjustment change the armhole?
Slightly, because the vertical spread crosses the armhole and enlarges it. Keep the change modest, re-true the armhole, and walk it against the sleeve cap to confirm they still match.
Can I make both adjustments on the same pattern?
Yes, and it is common. Use two separate slashes, one horizontal for rounded-back length and one vertical for broad-back width, so each dimension stays under control.
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