Goat Gestation Calculator (kidding date from the breeding date, 145–155 days)

Understanding the goat gestation calculator — concept and principle

This calculator gives a doe's expected kidding date and normal window from the breeding date, plus how far along she is today and when the last six weeks begin. Goat keepers use it to plan feeding, kidding pens and vet visits.

Counting 150 days: with the default inputs the result is Jan 24, 2027 (expected kidding).

How it is calculated

Expected kidding = breeding date + 150 days.
Normal window = day 145 to day 155.
Days pregnant = today − breeding date; days to due date = 150 − days pregnant.
Week of pregnancy = floor(days ÷ 7) + 1; progress = days ÷ 150.
Final six weeks begin at day 108.
Stage: before day 145, inside the window (145–155), or past the window.

The principle

Goats carry their kids for 145–155 days, 150 on average. About 80% of fetal growth happens in the last six weeks, so the doe's energy needs rise sharply then, while the growing uterus leaves less room for the rumen. That combination makes late pregnancy the time when pregnancy toxaemia is most likely, especially in does carrying twins or triplets. Marking day 108 helps you plan the change in feeding in good time. If a buck ran with the does for several days, the true date is uncertain, so the window shifts later.

Worked example

Default inputs: bred on Aug 27, 2026, viewed on Nov 10, 2026.

Due date = Aug 27, 2026 + 150 days = Sun, Jan 24, 2027.
Window = Tue, Jan 19, 2027 (day 145) to Fri, Jan 29, 2027 (day 155).
Days pregnant = 75; days to due date = 75; progress = 75 ÷ 150 = 50%.
Week = floor(75 ÷ 7) + 1 = 11; stage before the normal birth window.
Final six weeks begin at day 108 = Sun, Dec 13, 2026.

How to read the result

Use the window, not just the due date. From about day 108, review late-gestation feeding with your vet or a nutritionist. In the last week or two, watch for udder filling, a softening of the ligaments near the tail and restlessness, and have a clean, dry kidding area ready.

Common mistakes

Entering the date the buck was removed rather than the first possible mating.
Waiting until the due date to adjust feeding.
Assuming every doe will kid on day 150.
Ignoring signs of illness in late pregnancy.

Keep in mind: This is an estimate, not a diagnosis. Call your vet if a doe goes well past day 155, strains without progress, or shows weakness or loss of appetite in late pregnancy.

Frequently asked questions

How long is a goat pregnant?

145–155 days, about 150 on average.

When does most fetal growth happen?

About 80% happens in the final six weeks.

How do I know a doe is close to kidding?

Signs include a filling udder, softened ligaments near the tail and restlessness, but timing varies.

Sources: MSD Veterinary Manual (professional version), J. L. Stewart, "Pregnancy in Goats"

Checked 9 Nov 2026. MSD Veterinary Manual (professional version), “Pregnancy in Goats” (J. L. Stewart): gestation 145–155 days, average 150 days; 80% of fetal growth in the final 6 weeks.

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