Mare Gestation Calculator - Horse Gestation

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Anna Szczepanek, PhD and Steven Wooding
Last updated: Dec 30, 2022

The mare gestation calculator will estimate your pregnant mare's foaling day (due date) and guide you through all the stages of the horse gestational period. 🐎

Read on to easily find out how to use the foaling calculator, what is the gestation period for a horse, and how to calculate it properly!

How long is a horse pregnant for?

A typical adult horse female (mare) goes into labor (foals) around 330-345 days after mating.

As we can see, the average horse pregnancy length is equal to 338 days (that is, a little over 11 months). However, we need to remember that large horses' pregnancies tend to last longer than the ones of tiny ponies.

As we all know, mares usually give birth to only one foal.

Curious about the pregnancies of other species? Now is just the right time to find out everything about them!

What is foaling?

Foaling describes a female horse (a mare) going into labor. The result of the entire process is, of course, a foal. 🐴

So just to confirm, delivery day = due date = foaling day and yes, our mare gestation calculator does compute them all!

How to use the mare gestation calculator?

Well, no horse gestation calculator could ever be easier! Enter the Mating date (successful breeding date) and receive the complete set of results, including:

  • Estimated foaling date, and its full range;
  • Current gestation day; and
  • Day of the week of predicted labor day.

So, our mare due date calculator allows you to monitor all your mare's pregnancy's essential dates carefully!

πŸ’‘ You still need to remember that pregnancy is an extremely individual matter, and some mares may foal successfully before or after estimated dates.

How to calculate foaling date with horse pregnancy length?

You can easily replicate the results of our horse gestation period calculator using a few easy equations:

  1. For the estimated delivery date:

    Foaling = MatingDate + 338

    338 days = 11 months

  2. For the full range of possible foaling days:

    Earliest possible foaling = MatingDate + 331

    Latest possible foaling = MatingDate + 346

πŸ’‘ You're probably wondering why we added an extra day to our calculations. It is because ovulation in horses, just like in humans, may last around 24 hours, allowing for the later fertilization of the egg. This simple trick allows our mare gestation calculator to be a little bit more precise. πŸ™‚

How far along is my mare?

If you know the breeding (mating) date, it's effortless to establish the day of your mare's pregnancy.

You may use the equation identical to the one used in our horse due date calculator:

Pregnancy day = Current date - Mating date

Happy with the mare days in foal calculator? Check out our other fancy animal tools!


When is breeding season for horses?

Breeding season for horses lasts through spring and summer β€” more specifically, from May till August. These are the months when the chances for pregnancy are the highest. 🎠

How do I calculate how far along my mare is?

To calculate how far along your mare is, follow these steps:

  1. Take the current date.
  2. Get the mating date.
  3. Subtract mating date from current date: Current date - Mating date
  4. Now you know how the current length of your horse's pregnancy! πŸŽ‰
  5. Keep in mind, the average horse pregnancy length is equal to 338 days.
Łucja Zaborowska, MD, PhD candidate
Mating date
Foaling date
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