Animal Gestation Calculator

Horse Gestation Calculator

Last updated

A horse's gestation period is about 340 days, or roughly 11 months, though it ranges from 320 to 370 days depending on breed and individual animal.

Calculate a foal due date

What do you know?

Estimated foaling date

Sunday, 3 October 2027

Earliest

13 Sept 2027

Latest

2 Nov 2027

340 days remaining0% complete

0 of 340 days elapsed

Milestone timeline

Key Horse pregnancy milestones with calculated calendar dates
DayMilestoneDate
16Ultrasound to check for twins13 Nov 2026
300Increase feed, begin foaling prep24 Aug 2027
320Move to foaling stall, remove Caslick if present13 Sept 2027
340Expected foaling3 Oct 2027

What to do next

How to use the horse gestation calculator

  1. 1. Choose what you know. Enter the breeding date to get a due date, or switch to the target due date mode to work backwards to the breeding date you need.
  2. 2. Refine the inputs. The calculator uses the 340-day average for this species.
  3. 3. Plan around the range. Use the earliest and latest dates and the milestone timeline to schedule checks, feed changes and preparation of the foaling area.

How long is a horse's gestation period?

The average is 340 days from breeding to foaling, about 11 months. Anything between 320 and 370 days is normal, and a typical litter is 1 foal. Treat the calculated date as the middle of that window rather than a fixed appointment.

Horse gestation table: breeding date to foaling date

Breeding dates one week apart with the matching foaling date at 340 days.

Twelve sample Horse breeding dates and their calculated due dates
Breeding dateExpected foaling date
28 Oct 20263 Oct 2027
4 Nov 202610 Oct 2027
11 Nov 202617 Oct 2027
18 Nov 202624 Oct 2027
25 Nov 202631 Oct 2027
2 Dec 20267 Nov 2027
9 Dec 202614 Nov 2027
16 Dec 202621 Nov 2027
23 Dec 202628 Nov 2027
30 Dec 20265 Dec 2027
6 Jan 202712 Dec 2027
13 Jan 202719 Dec 2027

Working backwards from a target foaling date

If you want foals on the ground in a particular week, switch the calculator to target date mode and enter the date you are aiming for. It subtracts 340 days to give the breeding date to book, plus the earliest and latest service dates that still land inside your window.

Horse gestation calculator FAQs

How do I calculate a horse due date?

Enter the breeding or mating date and the calculator adds the average horse gestation of 340 days. It also shows the earliest (320 days) and latest (370 days) dates that are still normal.

Should I use the first or last mating date?

If mating happened over several days, run the calculator for the first and the last date. The foal is most likely to arrive between the earliest result of the first date and the latest result of the last date.

Can I work out when to breed for a target horse due date?

Yes. Switch to target due date mode and enter the date you want; the calculator subtracts 340 days to give the breeding date, plus the earliest and latest breeding dates that still fit.

How accurate is the horse due date calculator?

It gives a planning estimate from published averages. Most births fall inside the 320–370 day window shown, but ask a vet to confirm the pregnancy and check anything outside that range.

More gestation pages

Livestock gestation chart