There's no one standard timetable for potty training -- the time it takes depends on how soon you start, how you define "toilet trained," and when your unique child hits her particular milestones. Normal potty-training behavior covers a wide range of possibilities. Still, most parents want at least a rough estimate of how long it will take to potty train, and you can probably guess if you know your child well.
Some children are simply quick learners, and if you've got a 3- or 4-year-old who's showing a strong interest in the potty and a desire to be a "big boy," you may have an easy time training him. In fact, some children learn to use the potty in as little as a day. Doing this takes intense focus on using the potty for the day (or two or three). Give your child lots of fluids and make several trips to the potty. When he goes, celebrate his success. If your child is definitely ready, this can work for you.
Most children take longer than a few days to learn to use the potty. The American Academy of Pediatrics states that it takes most children who are developmentally ready around six weeks to complete the potty-training process. Even those children who are potty-trained during the day may still wet the bed at night for several years. Bed-wetting is normal in children up to 7 years old, but you can always talk to your child's doctor if you are concerned.
Speeding It Up
If you prefer the potty-training process to go as quickly as possible, it's important to wait until your child is really ready to do it herself. She should be able to stay dry for a few hours at a time and start showing interest in using the potty. Purchase a child-sized potty and underwear that she chooses to get her excited about this milestone, and offer rewards like stickers, candies or toys to encourage her to use the potty.
Slip-Ups and Regression
You can consider your child trained when he tells you he has to go to the potty and makes it there most of the time. Some children will still have the occasional accident, especially when they are engrossed in play or in an unfamiliar environment. It's also normal for your child to experience some potty-training regression -- accidents that occur after a big change, such as a move or a new sibling.