when do dogs go into heat

Dogs typically go into heat (their first estrus cycle) around 6 months of age, but this can vary widely depending on the breed and size of the dog. Smaller dogs often experience their first heat between 6 to 7 months, medium-sized dogs between 7 to 9 months, and larger breeds may not go into heat until 12 to 24 months. Some dogs can start as early as 4 months, and others as late as 2 years old. After the first heat, dogs usually go into heat about twice a year, approximately every 6 to 7 months. The heat cycle lasts about 2 to 4 weeks, including different phases where the dog is fertile and can become pregnant.