This comes hand in hand then with the additional ability to be able to increase the interval between voids. Most will attain it by three years of age. Another component of readiness is physical readiness. If a child is not bothered by a wet or dirty diaper, if she is uninterested or unwilling to sit on the potty, believe me, you are not going to get very far. As the saying goes, you can place a toddler on a potty, but you can't make her pee.
Toddlers quickly learn that they can control their bodily functions.
Once your child is showing all these components of toilet training readiness, most experts recommend waiting at least three months before you start toilet training to ensure that all is set. Last but not least, look at yourself and your family situation. In order for toilet training to be as painless and smooth as possible, make sure that you AND your child are ready. Some kids toilet train quite easily, while for others it becomes what seems like a long drawn out battle. If you are incredibly busy at work, moving to a new house or a new baby is due soon, it's ok to wait a few months to let things settle down.