Most dogs whelp between 58 and 68 days after mating.
Pregnancy Milestones
How to Use the Dog Pregnancy Calculator
A dog's average gestation period is 63 days (approximately 9 weeks), though it can vary between 58 and 68 days. To use this tool, simply input the date of the first mating. Our calculator adds 63 days to provide an estimated whelping date and provides a window of safety for when you should prepare the whelping box.
Example Calculation
If your dog was successfully bred on January 1st, her estimated timeline would be:
Estimated Due Date: March 5th
Earliest Possible (Day 58): February 28th
Latest Likely (Day 68): March 10th
Stages of Canine Gestation
Trimester 1 (Days 1-21): The embryos move into the uterine horns. By the end of this stage, a veterinarian may be able to detect heartbeats via ultrasound.
Trimester 2 (Days 22-42): This is when the development of organs, claws, and whiskers begins. The mother's weight will begin to increase noticeably.
Trimester 3 (Days 43-63): The fetuses develop into recognizable puppies. You will notice significant mammary gland development and may even feel the puppies moving in the final week.
Signs of Impending Labor (Whelping)
As the calculated due date approaches, watch for these specific signs:
Temperature Drop: A dog's rectal temperature usually drops below 99°F (37.2°C) about 12-24 hours before labor begins.
Nesting Behavior: Shredding blankets or seeking out a quiet, secluded area.
Loss of Appetite: Many dogs stop eating 12 to 24 hours before whelping.
Restlessness: Shivering, panting, or pacing.
function calculateDogPregnancy() {
var inputDate = document.getElementById('matingDate').value;
var resultArea = document.getElementById('result-area');
if (!inputDate) {
alert('Please select a valid mating date.');
return;
}
var matingDate = new Date(inputDate);
// Calculation Logic
// Avg: 63 days, Min: 58 days, Max: 68 days
var estDue = new Date(matingDate);
estDue.setDate(matingDate.getDate() + 63);
var minDue = new Date(matingDate);
minDue.setDate(matingDate.getDate() + 58);
var maxDue = new Date(matingDate);
maxDue.setDate(matingDate.getDate() + 68);
// Milestones
var tri1End = new Date(matingDate);
tri1End.setDate(matingDate.getDate() + 21);
var tri2End = new Date(matingDate);
tri2End.setDate(matingDate.getDate() + 42);
// Calculate days remaining
var today = new Date();
today.setHours(0,0,0,0);
var timeDiff = estDue.getTime() – today.getTime();
var daysLeft = Math.ceil(timeDiff / (1000 * 3600 * 24));
// Format dates
var options = { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' };
document.getElementById('estDueDate').innerText = estDue.toLocaleDateString(undefined, options);
document.getElementById('dateRange').innerText = minDue.toLocaleDateString(undefined, { month: 'short', day: 'numeric' }) + " to " + maxDue.toLocaleDateString(undefined, { month: 'short', day: 'numeric', year: 'numeric' });
var countdownText = "";
if (daysLeft > 0) {
countdownText = "Approximately " + daysLeft + " days remaining until whelping.";
} else if (daysLeft === 0) {
countdownText = "The estimated due date is today!";
} else {
countdownText = "The estimated due date has passed.";
}
document.getElementById('daysRemaining').innerText = countdownText;
// Timeline text
document.getElementById('trimester1').innerHTML = "End of First Trimester: " + tri1End.toLocaleDateString() + " (Embryos established)";
document.getElementById('trimester2').innerHTML = "End of Second Trimester: " + tri2End.toLocaleDateString() + " (Growth phase begins)";
document.getElementById('trimester3').innerHTML = "Final Stage: Watch for nesting behavior after " + minDue.toLocaleDateString();
resultArea.style.display = 'block';
resultArea.scrollIntoView({ behavior: 'smooth' });
}