Estimate Your Mare’s Foaling Due Date
Horse Pregnancy Calculator for Foaling Due Date Planning
This calculator helps you estimate a mare’s foaling due date using the breeding or ovulation date and a gestation length in days. Because mares can foal earlier or later than an estimate, the calculator also provides a practical due window and a clear progress indicator.
How the calculation works
The core estimate uses a simple date offset:
\(D_{due} = D_{breed} + G\)
Where \(D_{breed}\) is the breeding/ovulation date and \(G\) is the gestation length in days.
The due window is calculated as:
\(D_{start} = D_{due} - W\)
\(D_{end} = D_{due} + W\)
Where \(W\) is the window size in days.
How to use the results
- Estimated due date is a planning anchor, not a guarantee.
- Due window helps you prepare for earlier or later foaling within a reasonable range.
- Progress is shown as a percent of gestation completed: \(P = \frac{\text{days pregnant}}{G}\times 100\%\).
Timeline table and practical checkpoints
The timeline table converts common planning checkpoints into real calendar dates based on your input. Examples include an early pregnancy scan window, a heartbeat detection window, an early fetal sexing window, trimester markers, and final-month preparation timing. The exact schedule can vary by mare, farm protocol, and veterinarian preference.
Notes and safety
This tool provides an estimate for planning and record-keeping. If your mare is past the end of the due window or you notice concerning signs, consult a qualified veterinarian.