Foaling date calculator
Horse gestation calculator
A mare carries her foal for about 340 days, usually 335 to 342, though healthy pregnancies run from about 320 to 370 days. Enter the covering or insemination date — or the first and last cover — to see the expected foaling date with its early and late edge, then watch the mare for signs across the whole period.
Horse foaling date calculator
Enter one breeding date, or the first and last day the male ran with the group. Work back from a target birth date with “Plan backward”.
- Earliest reference
- Sat, Apr 3, 2027
- Central reference
- Thu, Apr 8, 2027
- Latest reference
- Sat, Apr 10, 2027
- Outer breeding window
- —
- Reference breeding band
- —
Horses: 2026-05-03 + 335 days = 2027-04-03 · + 340 days = 2027-04-08 · 2026-05-03 + 342 days = 2027-04-10 · window 8 days
Nothing you enter leaves your browser. Dates are planning references, not guarantees.
Example: a mare covered on May 3
Early edge (335 days): Sat, Apr 3, 2027
Planning date (340 days): Thu, Apr 8, 2027
Late edge (342 days): Sat, Apr 10, 2027
Have the foaling stall ready by: Sat, Mar 13, 2027 (three weeks before the early edge)
If she was covered on May 3 and again on May 5, enter both days: the planning band becomes Thu, Apr 8, 2027 – Sat, Apr 10, 2027 and the late edge moves to Mon, Apr 12, 2027.
The window from the calculator is the usual range, not the full one. Minnesota Extension notes that individual mares occasionally foal anywhere from 315 to more than 400 days, so treat the late edge as “start watching closely”, not “something is wrong”.
Planning a foal for spring 2028
To aim for foals born in April 2028, working back with the horse profile gives a reference breeding band of Tue, Apr 27, 2027 – Wed, May 26, 2027 (outer bounds Sun, Apr 25, 2027 – Mon, May 31, 2027).
Which horse gestation length does the calculator use?
- Minimum
- 335 days
- Reference
- 340 days
- Maximum
- 342 days
The 335–342-day range is the one University of Minnesota Extension gives for a normal pregnancy. The 340-day planning date matches Penn State Extension (“most mares delivering around the 340-day mark”) and sits inside Nebraska Extension’s 335–340 days. These are the horse values built into the Livestock Gestation Tracker app.
How much does gestation vary between mares and equids?
| Animal or group | Gestation (days) | Source |
|---|---|---|
| Mares, usual range | 335–342 | University of Minnesota Extension |
| Mares, occasional extremes | 315 to over 400 | University of Minnesota Extension |
| Mares, usual / possible | 335–340 / 320–370 | University of Nebraska–Lincoln Extension |
| Mares, range and typical | 330–370, most around 340 | Penn State Extension |
| Foal considered premature | born before 320 | Penn State Extension |
| Thoroughbred mares (one stud, 118 pregnancies) | mean 335 | Kulisa et al., 2009 |
| Mares carrying horse foals vs mule foals (one study) | 347.2 vs 341.1 | Boakari et al., 2019 |
| Donkey | about 365 | MSD Veterinary Manual |
The Thoroughbred study found colts carried slightly longer than fillies (about 336.7 against 335.1 days), but the difference was not statistically significant.
What are the signs a mare is about to foal?
- Two to six weeks out: the udder develops, growing quickly in the last two weeks (Nebraska; Minnesota). Penn State also mentions belly swelling and relaxation of the vulva and tailhead around a month before.
- Four to six days before: milk can often be found in the teats (Nebraska).
- One to two days before: “waxing” — beads of dried colostrum on the teat ends — usually appears (Nebraska; Minnesota says about one day).
- Milk chemistry: calcium test strips or a milk pH below 6.5 point to foaling soon, though no test is foolproof.
How do I prepare for foaling?
- Pre-foaling vaccinations in the last three to six weeks of pregnancy, as your veterinarian advises — Minnesota Extension advises no vaccines in the first 60 days
- A foaling stall of at least 14 × 14 feet, stripped, disinfected and bedded deep with clean straw rather than shavings; move the mare in two to three weeks before her date
- Your veterinarian’s number, a flashlight, tail wrap, halter and lead
- Clean towels, gloves, scissors, umbilical tape and navel dip, an enema and a nasal aspirator (Penn State’s foaling kit)
When should I call the vet during foaling?
Foaling is fast. Minnesota Extension describes a first stage of one to six hours, then the white amnion should appear within about ten minutes of the water breaking and the foal is usually delivered in about 20 minutes. Call your veterinarian if the amnion or a foot has not appeared within about ten minutes of the water breaking, if progress stops for more than ten minutes, if a red velvety bag appears first (a “red bag” — Penn State says call immediately), if the foal is presented wrongly, or if the placenta has not passed within three hours.
Livestock Gestation Tracker is an organizational aid, not veterinary advice. Reference dates vary by animal, breed, pregnancy and management conditions. Use your own records and your veterinarian or a qualified livestock professional for care decisions.
Sources
- University of Minnesota Extension — Caring for your mare during breeding and foaling
- University of Nebraska–Lincoln Extension G1874 — The foaling mare
- Penn State Extension — Foaling season: tips for delivery
- MSD Veterinary Manual — Approximate gestation periods (donkey)
- Boakari et al. (2019), Reproduction in Domestic Animals — Are mule pregnancies really longer than equine pregnancies?
- Kulisa et al. (2009) — Chosen factors affecting the gestation length of Thoroughbred mares
Questions people ask
How long is a horse pregnant?
About 11 months. University of Minnesota Extension gives 335 to 342 days as the usual length, with occasional pregnancies from 315 to over 400 days; Penn State says most mares deliver around day 340.
When is my mare due if she was covered on May 3?
Using 340 days she is due around April 8, 2027. The 335–342-day profile puts foaling between April 3 and April 10, 2027 — but because mares vary so much, keep watching for signs well after the latest date.
Is a mare overdue at 350 days?
Not necessarily. University of Nebraska–Lincoln Extension reports gestations from 320 to 370 days and Penn State from 330 to 370. A long pregnancy alone is common; ask your veterinarian to check a mare that is well past her date or shows any sign of illness.
What is the milk test for foaling?
As foaling nears, calcium (and magnesium) in the mare’s udder secretion rises. Nebraska Extension describes test strips sampled daily for about ten days before the expected date; Penn State notes that a milk pH below 6.5 usually means foaling is near. Minnesota Extension cautions that no test is foolproof.
Do donkeys and mules use the same calculator?
No. The MSD Veterinary Manual lists about 365 days for donkeys, and research on mares carrying mule foals found a mean of about 341 days against 347 days for the horse pregnancies in the same study. Add your own profile in the app for a donkey jenny.