What is the Gestation Calculator?
The Gestation Calculator estimates a due date by adding a chosen gestation period (in days) to a conception date. It is flexible enough for human pregnancies (typically about 266 days from conception, or 280 days from the last menstrual period) as well as for animals, each of which has its own gestation length — for example dogs (~63 days), cats (~64 days), cows (~283 days), and horses (~340 days).
How to use it
Pick the conception date, then enter the gestation period in days. The calculator returns the estimated due date along with the equivalent number of gestation weeks. Adjust the gestation days to match the species or your clinician's guidance.
The formula explained
The math is a simple calendar addition: $$\text{Due Date} = \text{Conception Date} + \text{Gestation Period (days)}$$ The calculator handles month lengths and leap years automatically, then divides the gestation days by 7 to express the period in weeks.
Worked example
Suppose conception occurred on 1 January 2024 and you use a human gestation period of 266 days. Adding 266 days to 1 January 2024 lands on 23 September 2024. That equals $$266 \div 7 = 38$$ weeks of gestation.
FAQ
Is this a medical tool? No. It is an estimate. Due dates vary, and only a healthcare professional can confirm pregnancy dating.
Why 266 days for humans? Average human gestation is roughly 266 days from conception (about 280 days, or 40 weeks, when counted from the last menstrual period).
Can I use it for animals? Yes — just enter that species' typical gestation length in days.
