Dog heat cycle calculator

Enter the first day of her last heat, and earlier heats if you know them. You get the date of the next heat, when to start progesterone tests, and the heat after that. It uses the same method as the Sire & Dam app.

Guidance only – always follow your vet. Values are averages from standard veterinary reproduction references; labs, breeds and dogs vary.

How the next heat is predicted

• With one heat date, the next heat is expected about 6 months (183 days) later, a typical interval.
• With two or more, the calculator uses her own average gap between heats, from the last four gaps at most, because recent cycles say more about the next one.
• Gaps shorter than 3 months or longer than 15 months are ignored as missed or mistyped heats.
• Example: heats on 15 January 2026, 20 July 2026 and 18 January 2027 give an average of 184 days, so the next heat is expected on 21 July 2027.

How often do dogs come into heat?

Most bitches come into heat about every 6 months, but anything from about 4 to 12 months can be normal for an individual dog. Some breeds, such as the Basenji, usually cycle only once a year, and many large and giant breeds have longer gaps. What matters most is her own pattern: once you have logged a few heats, the prediction follows her rhythm.

The stages of the heat cycle

• Pro-oestrus (on average about 9 days): swelling and bloody discharge; males are interested, but she does not accept them yet.
• Oestrus (on average about 9 days, but very variable): she accepts the male; ovulation happens in this phase. Progesterone tests pin down the day.
• Dioestrus (about 2 months): after ovulation, whether she is pregnant or not.
• Anoestrus: the resting phase until the next heat.

Frequently asked questions

When should I start progesterone testing?

Around day 5 or 6 of the heat, counting the first day of bleeding as day 1, then every 2–3 days. Use the progesterone chart to read the results.

How long does a dog stay in heat?

The whole heat (pro-oestrus and oestrus) usually lasts about 2 to 3 weeks, but it varies a lot between dogs and from heat to heat.

Her heats are irregular. Is that normal?

Some variation is normal, especially in young bitches. Very short intervals, heats far apart or a missed heat are worth a check with your vet.

Can the calculator tell me when she is fertile?

Only roughly. The heat date tells you when to start testing; the fertile days come from progesterone tests, because ovulation day differs a lot between dogs and between heats.

More free breeding tools

• Dog pregnancy calculator: whelping date and a day-by-day pregnancy timeline
• Progesterone levels chart and ovulation calculator: ovulation day and best days to breed
• Puppy weight gain calculator: checks whether a newborn puppy is gaining enough
• Sire & Dam app: heats, progesterone, pregnancies and litters in one place