On average, girls are potty trained by 29 months, according to the University of Michigan Health System. Girls typically learn to control their bladder muscles and bowel before boys, who are trained at an average age of 31 months. However, toddlers become ready for potty training at different rates, so don't push your daughter to start training before she's ready.
Toddlers aren't ready for potty training until they are able to communicate their needs, walk to the potty and pull down their pants, follow simple directions and have a desire for independence, according to the University of Michigan Health System. Most girls become interested in using the potty around 24 months, according to a 2002 study published in "Pediatrics." Around 26 months, girls are typically able to stay dry for two hours and communicate that they need to use the bathroom.
Children develop at different rates, so don't worry if your daughter doesn't reach toilet training readiness milestones as soon as other children. The normal age range of developing readiness skills can differ by up to a year, reports "Pediatrics." Pushing your daughter to potty train before she's ready may just cause the training process to take longer. Starting training during a stressful time, such as a family move, can also make the process more difficult. Most children -- 98 percent -- are trained by 3 years of age, according to the University of Michigan Health System.
Trends in Toilet Training
The age at which children are toilet trained hasn't always been the same. In the 1940s, for example, most toddlers began potty training before they reached 18 months of age, according to a 2008 report in "American Family Physician." White parents also tend to begin training later than African American parents. According to data collected on 248 children by the Children's Hospital of Pittsburgh, African American toddlers, on average, completed toilet training by 24 months, while white toddlers averaged 31 months of age.
Deciding When to Train
Potty training your daughter before she's ready can be frustrating and extend the process, but delaying potty training too long can have negative consequences, too. Late toilet training contributes to higher costs for parents, environmental problems caused by non-biodegradable diapers and higher rates of diarrhea or hepatitis A caused by diaper changes at daycare, according to "American Family Physician." Some daycare facilities also won't accept children who aren't toilet trained. If you're unsure when to begin potty training, consult your daughter's pediatrician.