How the heat cycle estimate works
Estimating a heat cycle means taking the day the last heat started, applying an interval, and reading off the next likely start. Enter only the most recent date and the tool uses a size bracket value; add one or two earlier dates and it switches to the average of your own intervals. The result line always says which basis was used.
The bracket values follow the veterinary description that intervals average about six months with a reported range of 4 to 12 months, that toy and small dogs are reported at 4 to 6 months, and that large dogs often cycle about once a year. The size boundary of about 45 lb is shown on screen. Content is current as of October 2026.
No recognized breed-by-breed conversion table for heat intervals exists, so this tool offers size brackets and a custom field instead of a breed list, and the output is a plain extension of what you entered rather than a prediction. It does not cover ovulation timing or breeding windows. 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
With one date the tool uses the size bracket value as the interval and shows the reported 4 to 12 month range as the window. Add a second or third date and it switches to your own average and your own shortest-to-longest range.
Intervals vary a lot between individuals, so being weeks off is common. If the gap keeps stretching, or you see bleeding or appetite changes along with it, have your veterinarian examine her.
No. The tool only extends the start of the previous heat and says nothing about ovulation timing. Plan breeding with your veterinarian using hormone testing.