Horse Gestation Calculator
without the guesswork.
Horse Mare 340 Day Foaling Calculator — Use 340 days as an average planning point alongside veterinary pregnancy checks, the wide normal gestation range and foaling-emergency override. Uses a focused calculator with visible assumptions. Inputs stay in your browser.
The 340-day date is an average planning point, not a due date. Merck reports that normal gestation can range from about 310 days to beyond 370 days, and pre-foaling signs do not precisely predict delivery.
Context matters.
- Do not induce delivery or judge fetal maturity from a calendar alone. Merck notes that inaccurate breeding dates can contribute to iatrogenic prematurity.
- Udder development, waxing and other premonitory signs are useful observations but cannot precisely predict foaling time.
- A red bag, severe distress, abnormal presentation or a foaling process that is not progressing is an emergency.
Sources & scope
This page shows the source trail, jurisdiction and review date alongside the result. Always confirm time-sensitive rules with the linked authority.
What to know before using the result.
Is day 340 a mare's due date?
No. It is an average planning point. Merck notes that normal gestation can range from about 310 days to beyond 370 days, so the mare and veterinary assessment control.
Which pregnancy checks are shown?
The timeline follows Merck's example schedule: days 14–18 for pregnancy and twins, days 25–30 for embryo development and days 40–60 for later fetal development.
Can waxing predict the exact foaling time?
No. Merck says premonitory signs are useful but do not precisely predict delivery. A red bag, abnormal presentation, severe distress or failure to progress is an emergency.