Biology
Mare Gestation Calculator (Horse)
Track a mare's pregnancy: enter the days since the last breeding date to see how far along she is, how many days remain, and the expected foaling window.
Your inputs
Change any value to update the result instantly.
Days until expected foaling
170 days
Pregnancy completed
50 %
Days elapsed
170 days
Stage
Second third of pregnancy
Normal range for this species
320–370 days (typical average 340)
Earliest expected day
320 days
Latest expected day
370 days
Extension practice adds 340 days to the last breeding date, but healthy foals arrive anywhere across roughly 320–370 days. Educational estimate only — confirm pregnancy and timing with a veterinarian; this tool is not veterinary advice.
What this calculator does
Projects a foaling window for a mare from the last breeding date using the 340-day extension standard.
What your result means
Days remaining to the expected foaling date, with the wide normal equine range shown.
Formula and working
days remaining = gestation length − days elapsed; progress = days elapsed ÷ gestation length × 100
- 1
Collect the inputs
Days since the last breeding date = 170 days; Gestation length used = 340 days
- 2
Apply the formula
days remaining = gestation length − days elapsed; progress = days elapsed ÷ gestation length × 100
- 3
Result
Days until expected foaling = 170 days
Frequently asked questions
Symbols and assumptions
- L
- Gestation length in days
- d
- Days elapsed since last breeding
- • 340 days added to the last breeding date; normal range roughly 320–370 days.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Equine gestation varies with season and individual mare; foaling watch should start well before the average date. Not veterinary advice.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Report a mistake or request an improvement
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