Horse Heat (Estrus) Cycle Calculator
Predict the next heat dates and best AI/service timing for a horse (mare) from the last observed heat (cycle ~21 days).
Optimal service/AI timing: breed every other day during estrus until ovulation; mares are long-day seasonal breeders. A mare's cycle averages 21 days with a long 5–7 day heat, mainly in spring and summer.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Breeders use the free Horse Heat Cycle Calculator to predict the next heats and time insemination correctly — the single biggest driver of conception rate.
About Horse Heat (Estrus) Cycle Calculator
Timing breeding to the heat (estrus) cycle is what makes the difference between a pregnant animal and a wasted service. A mare's cycle averages 21 days with a long 5–7 day heat, mainly in spring and summer. From the last observed heat, this tool projects the next three expected heat dates and reminds you of the optimal service window (breed every other day during estrus until ovulation; mares are long-day seasonal breeders.) plus when to do a pregnancy check if she isn't seen in heat again. Good heat detection and timing lift conception rates and shorten the calving interval.
How to use Horse Heat (Estrus) Cycle Calculator
- 1Enter the date heat was last observed.
- 2Read the next expected heat dates.
- 3Time service/AI to the recommended window, and pregnancy-check if heat returns.
Why use Horse Heat (Estrus) Cycle Calculator?
- ✓Uses the correct ~21-day cycle for horse (mare)
- ✓Projects the next several heat dates
- ✓States the optimal AI/service timing
- ✓Free, instant and fully in-browser
Frequently asked questions
How long is the heat cycle of a horse?+
About 21 days. A mare's cycle averages 21 days with a long 5–7 day heat, mainly in spring and summer.
When is the best time to inseminate a horse?+
Best timing: breed every other day during estrus until ovulation; mares are long-day seasonal breeders.
What if the animal returns to heat after service?+
A return to heat at the next cycle usually means she didn't conceive — re-inseminate at that heat. If she doesn't return, pregnancy-check from the date shown to confirm.
Is this tool free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline at the farm and your data never leaves the device.
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