Calculator
Dog heat cycle calculator
Updated October 2026 · Information only, not veterinary advice
Step 1
When did her last heat start?
Count from the first day of vulvar swelling or bloody discharge.
Most dogs come into heat about every 6 to 7 months. The range is wide, and young dogs can be irregular.
Next heat expected
January 13, 2027
Heat usually lasts about 2 to 3 weeks, so expect it to run to around February 3.
Following heats
- July 13, 2027
- January 13, 2028
Ovulation in her last heat
Often around Jul 23 to Jul 27 (days 10 to 14), but it varies a lot between dogs. Only progesterone testing confirms the day.
These are estimates from a typical cycle. Her cycle can drift, so recalculate after each heat.
The four stages of the heat cycle
| Stage | Typical length | What happens |
|---|---|---|
| Proestrus | About 9 days (range 3 to 17) | Vulva swells and a bloody discharge appears. She attracts males but usually refuses to mate. |
| Estrus | About 9 days (range 3 to 21) | Discharge often lightens. She accepts males. Ovulation happens early in this stage. |
| Diestrus | About 2 months | Receptiveness ends. Her body behaves as if pregnant whether or not she is, which is why false pregnancy can occur. |
| Anestrus | About 4 to 5 months | The resting phase before the next cycle. |
Signs she is in heat
- Swollen vulva and a bloody or straw-colored discharge.
- Licking the area more often and urinating more frequently.
- Restlessness, flirty behavior or a change in mood.
- Attention from male dogs.
Questions
Frequently asked questions
How often do dogs go into heat?
Most dogs come into heat about every 6 to 7 months, but the normal range is wide, from about 4 to 12 months. Some giant breeds cycle roughly once a year, and young dogs can be irregular.
How long does a dog’s heat last?
The visible heat, from first swelling to the end of receptiveness, usually lasts about 2 to 3 weeks. The whole cycle including the resting phase is several months.
When is a dog fertile?
Ovulation often falls around day 10 to 14 after the first signs, but it varies widely. Progesterone testing from your vet is the reliable way to find it.
When is her first heat?
Usually between 6 and 12 months in small breeds and later, up to about 18 to 24 months, in some large and giant breeds.
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