Case 1
- Which day are you counting from?
- 20513
- What does that day mark?
- First mating she permitted
- Which end of the window?
- Earliest — the window opens
- Counting from which day?
- 20544
27
Open with these valuesDog Due Date Calculator
58days
Result: 58 daysCanine gestation is a window, not a day. From the first mating the Merck Veterinary Manual gives 58 to 72 days; from the LH surge or first progesterone rise, 64 to 66. A bitch first mated on 1 March 2026 can whelp from 28 April, which is 27 days away on 1 April, up to 12 May.
Worked examples
Case 2
- Which day are you counting from?
- 20513
- What does that day mark?
- First mating she permitted
- Which end of the window?
- Latest — the window closes
- Counting from which day?
- 20544
41
Open with these valuesCase 3
- Which day are you counting from?
- 20513
- What does that day mark?
- LH surge or first progesterone rise
- Which end of the window?
- Earliest — the window opens
- Counting from which day?
- 20544
33
Open with these valuesHow it's calculated
days left = anchor day + gestation days − reference day, never below zero
- StepPick the day you counted from and say what it marks: mating, LH surge, or ovulation.
- StepAdd the days that anchor allows — 58 or 72 from mating, 64 or 66 from the surge, 62 or 64 from ovulation.
- StepSubtract the reference day. An edge already past gives 0, never a negative number.
- ResultAdd the answer to the reference day to get the calendar date itself.
What this number means
A dog's due date is not a day, it is a window, and how wide that window is depends entirely on what you counted from. Measured from the first mating the bitch permitted, the Merck Veterinary Manual puts whelping anywhere between day 58 and day 72. That fifteen-day spread is not biological noise: sperm stays viable in the reproductive tract for a week or more, and a bitch will accept a mate days before or after she actually ovulates, so the mating date can sit anywhere relative to conception. Pin down the hormones and the spread collapses. From the LH surge or the first rise in progesterone above baseline, gestation runs 64 to 66 days. From ovulation itself it is 62 to 64. Those are the numbers a progesterone-timed breeding gives you, and they are why breeders pay for the testing. This page counts calendar days in UTC, so no time zone and no daylight-saving change can move an answer by a day. It has no opinion on breed, litter size or parity — the manual lists all three as influences on gestation length without giving a direction, so no adjustment is applied here. What this is not: it is not a substitute for a veterinary examination. The numbers come from a veterinary reference; the decisions about a specific pregnancy belong with a vet who can see the dog.
58–72 days from the first instance that the female permitted breeding.
No average from mating exists
The 63-day figure that circulates widely is not in the Merck Veterinary Manual. From mating the manual gives only a range, so this page gives only a range.
Day 68 is not the last day
Counted from the first mating the window runs to day 72, not 68. A narrower figure would tell you something has gone wrong four days too early.
Progesterone testing narrows it to three days
From the LH surge the range is 64 to 66 days instead of 58 to 72. If the exact date matters, the timing has to come from the hormone, not the calendar.
Commonly misread
Add 63 days to the mating date and that is the due date.
No veterinary source gives a single day from mating. The manual gives 58 to 72 days, and the calculator gives you both ends.
A late litter past day 68 means something is wrong.
Counted from mating, day 72 is still inside the normal range. Counted from ovulation, day 65 already is not.
The mating date is the conception date.
Sperm can stay viable for a week or more, and mating happens either side of ovulation. That gap is the whole reason the window is fifteen days wide.
Reference table
| Counted from | Window opens | Window closes | Span |
|---|---|---|---|
| First mating she permitted | day 58 | day 72 | 15 days |
| LH surge / first progesterone rise | day 64 | day 66 | 3 days |
| Ovulation | day 62 | day 64 | 3 days |
| First day of diestrus | day 56 | day 58 | 3 days |
Questions
How long are dogs pregnant?
Counted from the first mating the bitch permitted, 58 to 72 days. Counted from the LH surge or the first progesterone rise it is 64 to 66 days, and from ovulation 62 to 64.
How do I calculate my dog's due date?
Take the day you counted from, add the gestation days that anchor allows, and subtract today. A bitch first mated on 1 March 2026 can whelp from 28 April to 12 May.
Why is the window from mating so much wider?
Because a mating date is not a conception date. Sperm remains viable in the reproductive tract for a week or more, and a bitch will accept a mate on either side of ovulation.
Where does the 63-day figure come from?
It is a rounded average of the ovulation-anchored range that has spread far beyond it. The Merck Veterinary Manual gives 62 to 64 days from ovulation and no single figure at all from mating.
Does gestation length vary by breed?
The manual names breed, parity and litter size as influences on gestation length but gives no direction or size for the effect. This calculator therefore applies no adjustment for any of them.
Why does the answer never go negative?
Once the edge you asked about has passed, a countdown to it has no further reading, so the answer is 0. Switch to the other end of the window, or use the days-between-dates calculator to measure backwards.
Sources and last check
Information, not professional advice.