Mare Gestation Calculator

March 2024
A mare that bred on 5 Mar 2024 has an approximate foaling date of

Saturday, February 8, 2025

The foaling date could fall between 19 Jan and 5 Mar. Learn more about the Key Gestation Milestones.

Disclaimer: We've spent hundreds of hours building and testing our calculators and conversion tools. However, we cannot be held liable for any damages or losses (monetary or otherwise) arising out of or in connection with their use. Full disclaimer.

Equine Gestation Milestones

Key gestation milestones for mares are important markers that indicate the progress of the pregnancy and the development of the fetus. Here's a timeline outlining these milestones:

  1. Days 14-16 (19 Mar 2024) - Post-Ovulation: First opportunity to confirm pregnancy through ultrasound. Vets look for the presence of an embryonic vesicle.
  2. Day 25-30 (30 Mar 2024) - Heartbeat Detection: A critical milestone where the fetus's heartbeat can be detected via ultrasound. This is also a time when twins can be identified and managed if necessary.
  3. Day 40-45 (14 Apr 2024) - End of Embryonic Period: The transition from the embryonic to the fetal period. The risk of embryonic loss decreases significantly after this point.
  4. Day 60-65 (4 May 2024) - Sex Determination: It's possible to determine the sex of the foal via ultrasound.
  5. Day 150 (2 Aug 2024) - Fetus Resembles a Tiny Horse: By this time, the fetus has developed most of the adult features and begins to look like a miniature horse.
  6. Day 180 (1 Sep 2024) - Fetal Movement: The mare owner might start to observe fetal movements.
  7. Day 210 (1 Oct 2024) - Rapid Fetal Growth: The fetus enters a period of rapid growth which continues until birth.
  8. Day 270 (30 Nov 2024) - Colostrum Formation: The mare's body begins to prepare for foaling by starting colostrum production.
  9. Day 300 (30 Dec 2024) - Preparation for Birth: It's a good time to start preparing for the foaling, ensuring that all necessary supplies and facilities are ready.
  10. Day 320-345 (19 Jan 2025) - Final Stages: This is the typical range when most mares will foal, although some may go as long as 365 days. Owners should monitor for signs of impending birth, such as the mare's udder filling and the relaxation of the pelvic ligaments.
  11. Foaling (8 Feb 2025): The culmination of the gestation period. Most mares will foal quickly and without human intervention, but it's important to be prepared to assist or call a veterinarian if complications arise.

How Do You Calculate a Mare's Foaling Date?

4 young foals standing in front of a barn

Calculating a mare's foaling date involves a few straightforward steps. Here's a list to guide you through the process:

  1. Determine the Date of Conception: This is the day when the mare was successfully bred. If the exact date is unknown, use the last date of the breeding period.
  2. Understand the Average Gestation Length: The average gestation period for a mare is approximately 340 days, but it can range from 320 to 365 days.
  3. Adjust for Breed Variations: If you know the breed of the mare, adjust the average gestation period based on typical lengths for that breed (if available).
  4. Consider Seasonal Variations: Mares foaling in colder months might have a slightly longer gestation period, while those in warmer months might have a slightly shorter one.
  5. Account for Mare's History: If the mare has had previous foals, consider her past gestation lengths as they can be a good indicator of her usual gestation period.
  6. Regular Veterinary Check-ups: Regular check-ups can help estimate the foaling date more accurately, especially as the mare approaches the end of her pregnancy.
  7. Watch for Physical Signs: As the expected foaling date approaches, observe the mare for physical signs of impending birth, such as udder development and relaxation of the pelvic ligaments.
  8. Adjust Expectations: Be prepared for a range of possible foaling dates, as predicting the exact day is often challenging.
  9. Use a Gestation Calculator: To simplify the process, you can use our equine gestation calculator. You enter the date of conception, and it automatically calculates the estimated foaling date.

Keep detailed records of breeding, gestation, and foaling for future reference, as this data can be invaluable for managing subsequent pregnancies.

Gestation Periods For Different Mare Breeds

Below is a table showing the gestation periods for various breeds of mares. While there are average gestation lengths for different breeds, individual mares may deviate from these averages due to various factors like age, health, environment, and genetics.

Breed of MareAverage Gestation Period (Days)
Thoroughbred335 - 342
Arabian320 - 360
Quarter Horse330 - 345
Standardbred330 - 345
Warmblood335 - 345
Draft Breeds (e.g., Clydesdale, Shire)340 - 365
Pony Breeds (e.g., Shetland, Welsh)320 - 360
Miniature Horse320 - 335
Morgan335 - 340
Paint Horse330 - 345
Appaloosa335 - 345
Andalusian330 - 340
Friesian340 - 345
Tennessee Walking Horse335 - 345
Mustang335 - 360

Mare Gestation Reference Table

Below is a reference table showing the foaling date for all days of the year.

Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date Date ExposedFoaling Date
1 Jan6 Dec1 Feb6 Jan1 Mar4 Feb1 Apr7 Mar1 May6 Apr1 Jun7 May1 Jul6 Jun1 Aug7 Jul1 Sep7 Aug1 Oct6 Sep1 Nov7 Oct1 Dec6 Nov
2 Jan7 Dec2 Feb7 Jan2 Mar5 Feb2 Apr8 Mar2 May7 Apr2 Jun8 May2 Jul7 Jun2 Aug8 Jul2 Sep8 Aug2 Oct7 Sep2 Nov8 Oct2 Dec7 Nov
3 Jan8 Dec3 Feb8 Jan3 Mar6 Feb3 Apr9 Mar3 May8 Apr3 Jun9 May3 Jul8 Jun3 Aug9 Jul3 Sep9 Aug3 Oct8 Sep3 Nov9 Oct3 Dec8 Nov
4 Jan9 Dec4 Feb9 Jan4 Mar7 Feb4 Apr10 Mar4 May9 Apr4 Jun10 May4 Jul9 Jun4 Aug10 Jul4 Sep10 Aug4 Oct9 Sep4 Nov10 Oct4 Dec9 Nov
5 Jan10 Dec5 Feb10 Jan5 Mar8 Feb5 Apr11 Mar5 May10 Apr5 Jun11 May5 Jul10 Jun5 Aug11 Jul5 Sep11 Aug5 Oct10 Sep5 Nov11 Oct5 Dec10 Nov
6 Jan11 Dec6 Feb11 Jan6 Mar9 Feb6 Apr12 Mar6 May11 Apr6 Jun12 May6 Jul11 Jun6 Aug12 Jul6 Sep12 Aug6 Oct11 Sep6 Nov12 Oct6 Dec11 Nov
7 Jan12 Dec7 Feb12 Jan7 Mar10 Feb7 Apr13 Mar7 May12 Apr7 Jun13 May7 Jul12 Jun7 Aug13 Jul7 Sep13 Aug7 Oct12 Sep7 Nov13 Oct7 Dec12 Nov
8 Jan13 Dec8 Feb13 Jan8 Mar11 Feb8 Apr14 Mar8 May13 Apr8 Jun14 May8 Jul13 Jun8 Aug14 Jul8 Sep14 Aug8 Oct13 Sep8 Nov14 Oct8 Dec13 Nov
9 Jan14 Dec9 Feb14 Jan9 Mar12 Feb9 Apr15 Mar9 May14 Apr9 Jun15 May9 Jul14 Jun9 Aug15 Jul9 Sep15 Aug9 Oct14 Sep9 Nov15 Oct9 Dec14 Nov
10 Jan15 Dec10 Feb15 Jan10 Mar13 Feb10 Apr16 Mar10 May15 Apr10 Jun16 May10 Jul15 Jun10 Aug16 Jul10 Sep16 Aug10 Oct15 Sep10 Nov16 Oct10 Dec15 Nov
11 Jan16 Dec11 Feb16 Jan11 Mar14 Feb11 Apr17 Mar11 May16 Apr11 Jun17 May11 Jul16 Jun11 Aug17 Jul11 Sep17 Aug11 Oct16 Sep11 Nov17 Oct11 Dec16 Nov
12 Jan17 Dec12 Feb17 Jan12 Mar15 Feb12 Apr18 Mar12 May17 Apr12 Jun18 May12 Jul17 Jun12 Aug18 Jul12 Sep18 Aug12 Oct17 Sep12 Nov18 Oct12 Dec17 Nov
13 Jan18 Dec13 Feb18 Jan13 Mar16 Feb13 Apr19 Mar13 May18 Apr13 Jun19 May13 Jul18 Jun13 Aug19 Jul13 Sep19 Aug13 Oct18 Sep13 Nov19 Oct13 Dec18 Nov
14 Jan19 Dec14 Feb19 Jan14 Mar17 Feb14 Apr20 Mar14 May19 Apr14 Jun20 May14 Jul19 Jun14 Aug20 Jul14 Sep20 Aug14 Oct19 Sep14 Nov20 Oct14 Dec19 Nov
15 Jan20 Dec15 Feb20 Jan15 Mar18 Feb15 Apr21 Mar15 May20 Apr15 Jun21 May15 Jul20 Jun15 Aug21 Jul15 Sep21 Aug15 Oct20 Sep15 Nov21 Oct15 Dec20 Nov
16 Jan21 Dec16 Feb21 Jan16 Mar19 Feb16 Apr22 Mar16 May21 Apr16 Jun22 May16 Jul21 Jun16 Aug22 Jul16 Sep22 Aug16 Oct21 Sep16 Nov22 Oct16 Dec21 Nov
17 Jan22 Dec17 Feb22 Jan17 Mar20 Feb17 Apr23 Mar17 May22 Apr17 Jun23 May17 Jul22 Jun17 Aug23 Jul17 Sep23 Aug17 Oct22 Sep17 Nov23 Oct17 Dec22 Nov
18 Jan23 Dec18 Feb23 Jan18 Mar21 Feb18 Apr24 Mar18 May23 Apr18 Jun24 May18 Jul23 Jun18 Aug24 Jul18 Sep24 Aug18 Oct23 Sep18 Nov24 Oct18 Dec23 Nov
19 Jan24 Dec19 Feb24 Jan19 Mar22 Feb19 Apr25 Mar19 May24 Apr19 Jun25 May19 Jul24 Jun19 Aug25 Jul19 Sep25 Aug19 Oct24 Sep19 Nov25 Oct19 Dec24 Nov
20 Jan25 Dec20 Feb25 Jan20 Mar23 Feb20 Apr26 Mar20 May25 Apr20 Jun26 May20 Jul25 Jun20 Aug26 Jul20 Sep26 Aug20 Oct25 Sep20 Nov26 Oct20 Dec25 Nov
21 Jan26 Dec21 Feb26 Jan21 Mar24 Feb21 Apr27 Mar21 May26 Apr21 Jun27 May21 Jul26 Jun21 Aug27 Jul21 Sep27 Aug21 Oct26 Sep21 Nov27 Oct21 Dec26 Nov
22 Jan27 Dec22 Feb27 Jan22 Mar25 Feb22 Apr28 Mar22 May27 Apr22 Jun28 May22 Jul27 Jun22 Aug28 Jul22 Sep28 Aug22 Oct27 Sep22 Nov28 Oct22 Dec27 Nov
23 Jan28 Dec23 Feb28 Jan23 Mar26 Feb23 Apr29 Mar23 May28 Apr23 Jun29 May23 Jul28 Jun23 Aug29 Jul23 Sep29 Aug23 Oct28 Sep23 Nov29 Oct23 Dec28 Nov
24 Jan29 Dec24 Feb29 Jan24 Mar27 Feb24 Apr30 Mar24 May29 Apr24 Jun30 May24 Jul29 Jun24 Aug30 Jul24 Sep30 Aug24 Oct29 Sep24 Nov30 Oct24 Dec29 Nov
25 Jan30 Dec25 Feb30 Jan25 Mar28 Feb25 Apr31 Mar25 May30 Apr25 Jun31 May25 Jul30 Jun25 Aug31 Jul25 Sep31 Aug25 Oct30 Sep25 Nov31 Oct25 Dec30 Nov
26 Jan31 Dec26 Feb31 Jan26 Mar1 Mar26 Apr1 Apr26 May1 May26 Jun1 Jun26 Jul1 Jul26 Aug1 Aug26 Sep1 Sep26 Oct1 Oct26 Nov1 Nov26 Dec1 Dec
27 Jan1 Jan27 Feb1 Feb27 Mar2 Mar27 Apr2 Apr27 May2 May27 Jun2 Jun27 Jul2 Jul27 Aug2 Aug27 Sep2 Sep27 Oct2 Oct27 Nov2 Nov27 Dec2 Dec
28 Jan2 Jan28 Feb2 Feb28 Mar3 Mar28 Apr3 Apr28 May3 May28 Jun3 Jun28 Jul3 Jul28 Aug3 Aug28 Sep3 Sep28 Oct3 Oct28 Nov3 Nov28 Dec3 Dec
29 Jan3 Jan29 Mar4 Mar29 Apr4 Apr29 May4 May29 Jun4 Jun29 Jul4 Jul29 Aug4 Aug29 Sep4 Sep29 Oct4 Oct29 Nov4 Nov29 Dec4 Dec
30 Jan4 Jan30 Mar5 Mar30 Apr5 Apr30 May5 May30 Jun5 Jun30 Jul5 Jul30 Aug5 Aug30 Sep5 Sep30 Oct5 Oct30 Nov5 Nov30 Dec5 Dec
31 Jan5 Jan31 Mar6 Mar31 May6 May31 Jul6 Jul31 Aug6 Aug31 Oct6 Oct31 Dec6 Dec