Dog Heat Cycle Calculator
Predict your dog's next heat and fertile window from her last cycle.
Pets FitnessScience-backed formula
Enter your details
Fill in the fields, then calculate
Please choose a date.
Awaiting Data
Enter your details and tap Calculate to see your results appear here.
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ResultYour result appears here.
What it measures
Most dogs come into heat about twice a year, though small breeds cycle more often and giant breeds less. From the last heat, this tool predicts the next one.
Your pet's stats convert into friendly, human readable numbers.
The fertile window usually falls around days 9 to 14 of the cycle.
How to use this calculator
- Enter the last heat start date.
- Pick her usual cycle interval.
- Tap Calculate for the next heat and fertile window.
The formula used
Next heat = last heat + cycle interval
Fertile window \u2248 days 9 to 14
Fertile window \u2248 days 9 to 14
- last heat
- When the last cycle began.
- interval
- Months between cycles.
Understanding Your Results
Proestrus
Days 1 to 9
Swelling and discharge begin.
Estrus (fertile)
Days 9 to 14
The fertile window.
Next heat
After the interval
The predicted start.
Tips to Improve
- Track each cycle to learn her pattern.
- Keep her secure during heat.
- Ask your vet about spaying.
- Watch for irregular cycles.
Frequently Asked Questions
About every six months on average, varying by breed.
Usually days 9 to 14 of the cycle.
Around two to three weeks total.
Scientific References
- American Kennel Club. (2023). Dog estrous cycle.
- Concannon, P. W. (2011). Reproductive cycles of the domestic bitch. Animal Reproduction Science, 124(3-4), 200–210.