Do not rely on soaking or heating a leather jacket to produce controlled shrinkage. Such treatment can change the finish, distort panels and damage the lining. If the jacket is too large, first determine whether a measured alteration can solve the fit problem.
Measure the unwanted space
Try the jacket with your normal underlayer and close it. Check the shoulders, chest, waist and sleeves separately. A loose waist does not mean every part of the jacket needs to become smaller. Note which movement tests feel awkward and where the garment bunches.
Compare these observations with a jacket that already fits well. Keep garment measurements separate from body measurements. A supplier's size chart may describe either, so confirm the definition before ordering a replacement.
Consider changes at the seams
A leather alteration specialist can assess whether the body or sleeves can be taken in without disrupting pockets and hardware. Ask about visible needle holes and the lining. Some designs offer little room for a neat change.
If the shoulders and armholes are wrong, altering the waist alone may leave the jacket unbalanced. When buying new, exchange options can be more useful than a shrinkage experiment. For a vintage piece, preserving the existing leather may matter more than achieving a very close fit.
Will a dryer make it one size smaller?
There is no reliable one-size result. Different parts may react differently, and damage may be permanent. Avoid methods promising an exact percentage of shrinkage. Choose a target measurement and a construction-based solution instead.
Related reading
Agreeing jacket measurement methods and tolerances. For another useful reference, see Fitting outdoor team jackets across sizes.
