Unfortunately, reducing a garment by a dress size involves multiple alterations—such as sleeve shortening, cropping, narrowing shoulders, etc. Additionally, sizes can vary significantly across brands, so we’re unable to use this as a definitive guideline.
Taking in a garment too much can warp the original shape, and so typically if it is more than ~2" per seam, we would not recommend it.
The best option if you are unsure if to come and have your garment fitted by one of our expert tailors in either Selfridges London, or Westfield Stratford, who can advise you on your best options.