Knowing roughly when a first heat is due helps you plan a neutering conversation and manage walks ahead of time. Enter the date of birth and this calculator turns the most common window, the usual window and the full reported range into actual dates, then shows where today sits among them.
The figures used are an average first heat at 6 to 12 months of age for dogs, most within 6 to 18 months, and a full reported span of 4 to 24 months. Recommendations around the timing of neutering are judged for the individual dog by your veterinarian, following the AAHA life stage guidelines. Guidance current as of October 2026.
No recognized table of first heat age by body size could be confirmed. This tool therefore offers no size selector, and it does not calculate the next heat date for a dog that has already cycled. That calculation belongs to the heat cycle tool, which works from the last heat date. This tool is for reference only and does not replace veterinary care. Contact your veterinarian right away if you notice symptoms or suspect a problem.
Frequently Asked Questions
No recognized table setting out first heat age by body size could be confirmed. Smaller dogs are reported to start earlier and larger ones later, but there is no basis for splitting that into numbers, so only the overall ranges are shown.
The reported figures come in layers. The average is 6 to 12 months, most dogs fall within 6 to 18 months, and reports overall span 4 to 24 months. The width depends on which layer you look at, so all three are shown together.
Typical signs are vulvar swelling, bleeding, more frequent urination and increased interest from males. If it is the first time and you are unsure, or bleeding carries on for a long time, have your veterinarian confirm it.