Dog Heat Cycle Calculator

Most dogs go into heat every 6 months (twice a year). However, this varies by breed and individual. Small breeds may cycle every 4 months, while giant breeds may only cycle once a year. Young dogs may have irregular cycles until they mature.

A dog's heat cycle lasts 2-4 weeks total. The fertile period (estrus) lasts 5-14 days within this cycle. The entire reproductive cycle, including the resting phase, spans about 6 months before the next heat begins.

Early signs include: swollen vulva, bloody vaginal discharge, increased urination, behavior changes (clingy or restless), licking genital area, and males showing interest. These signs appear in the proestrus stage, about 7-10 days before the fertile period.

Dogs are most fertile during estrus (standing heat), typically days 10-14 of the cycle. Signs she's fertile: discharge becomes lighter/straw-colored, she 'flags' her tail to the side, and she'll stand still when approached by a male. Ovulation usually occurs 2-3 days into estrus.

Small breeds typically have their first heat at 6-9 months old. Medium breeds at 9-12 months. Large and giant breeds may not have their first heat until 12-24 months old. Early spaying is recommended if you don't plan to breed.