Leather boots may be stretched, though not very much. The foot may be stretched about 1/2 size wider (such as from a “D” to an “E” width). The foot cannot be stretched longer, such as from an 11 to a 12. Boot calfs may also be stretched by up to 1/2“ (1cm) if they are unlined, or about 3/8” (.7cm) if they are lined with leather.
The most optimal way to have boots stretched is to take them to a cobbler. Not a guy in a dry-cleaning shop, but a real cobbler. Look for “leather or boot repair” shops in local telephone directories or on-line. Another place to check are shops that advertise “luggage repair.”
A cobbler has professional equipment made specifically for the purpose of stretching leather. It may take one to two weeks, and may cost US$40 to $70, depending on the difficulty of the job and your location.
If you want to try to stretch boots yourself plan to take time. Leather will stretch, but it takes a lot of time for the leather fibers to conform to a new shape. Don't simply pull on boot shafts and expect them to stay that way.
Most often, a boot calf feels narrow, or tight, on the legs. This happens as one ages and loses muscle tone. You may also wish to make boot calfs wider to accommodate leathers, breeches, or jeans worn inside of the boots.
You will need these materials: wood blocks, brown kraft (“butcher”) paper, isopropyl (rubbing) alcohol, and some cotton rags or a roll of paper towels. (Note, “boot stretching liquid” is isopropyl alcohol. You can pay 5x for a bottle of “boot stretching liquid” from an internet vendor for the same stuff you can find on a drugstore shelf at a much lower price.)
Pour some alcohol onto a rag or paper towel and use it to apply alcohol to the inside of the boot shaft. Get it good and wet.
Then insert wood blocks and paper so that the leather is pushed outward. Make it as tight as you can, because the leather will want to return to its usual shape when you remove the materials.
Place the boots in a well ventilated area, but out of direct sunlight. Do not put them in an oven or other warm place. While the alcohol is not flammable, it can be smelly, so you may want to put the boots in a safe, ventilated, shaded outdoor area. The alcohol will not take long to dry. However, the boots will take a long time to reshape, so leave them just as they are for about one week. After that, remove the materials you inserted into the boots and see how they fit. You may have to repeat the process once or twice. If after doing this three times (over three weeks) you still are unable to get the boots to become as wide as you want, stop. The boots will not stretch any more without damaging the leather and ruining the boot.
Most often there is just one part of a boot foot that is causing a problem, such as rubbing on a bunion or a place that causes blisters. What you need to do is “spot stretching.”
You will need these materials: one small wood block (about 1“ x 3” or 2cm x 7cm), brown kraft (“butcher”) paper, isopropyl (rubbing) alcohol, and some cotton rags or a roll of paper towels. (See the note above about “boot stretching liquid.”)
Pour some alcohol on a rag or paper towel, then use it to apply the alcohol to the inside of the boot foot in a large area around where the problem is. Get it good and wet.
Then insert the wood block using the narrow end to push against the leather from the inside so leather is pushed outward. Make it as tight as you can.
Place the treated boot in a well ventilated area (see above) for about a week. After that, remove the materials you inserted into the boots and see how they fit. You may have to repeat the process once or twice. If after doing this three times (over three weeks) you still are unable to fix the problem, stop. The boots will not stretch any more without damaging the leather and ruining the boot.
If you have a number of boots to stretch such that the cost of a cobbler's services would be very high in total, you may consider buying a “boot stretcher” available from some commercial vendors, such as Healing Touch. BHD, the owner of this wiki, bought one “combo” boot stretcher and has been pleased with it. Of course, it takes twice as long to stretch one pair of boots, since the boot stretcher can be used in only one boot at a time over one-week intervals.