Pregnancy Due Date Calculator
Due date and trimester milestones from your last period.
Enter your values
Enter the days since your last period started in days.
Enter the usual cycle length in days.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Days until due date
- 210 days
- Gestational age
- 10 weeks 0 days
- Current trimester
- First trimester
- Progress
- 25%
Quick answer
Naegele's rule sets the due date 280 days after the first day of the last menstrual period, adjusted for cycle length.
Due date = LMP + 280 days
At a glance
| What it does | Due date and trimester milestones from your last period. |
|---|---|
| Category | Health |
| Inputs needed | Days since your last period started, Usual cycle length |
| Main output | Days until due date |
| Formula | Due date = LMP + 280 days |
| Cost | Free — no sign-up, no download |
How to use the Pregnancy Due Date Calculator
- 1Count the days since your last period began.
- 2Enter your usual cycle length.
- 3Read the due date countdown and trimester.
Inputs explained
- Days since your last period started(days)
- Enter the days since your last period started in days.
- Usual cycle length(days)
- Enter the usual cycle length in days.
Worked example
Using the values the calculator loads with:
Inputs
- Days since your last period started70 days
- Usual cycle length28 days
Results
- Days until due date210 days
- Gestational age10 weeks 0 days
- Current trimesterFirst trimester
- Progress25%
Frequently asked questions
How accurate is the due date?
Only about 4% of babies arrive on the exact date; 80% arrive within two weeks either side.
What if my cycle is not 28 days?
The tool shifts the due date by the difference, since ovulation timing moves with cycle length.
What do I need to enter into the Pregnancy Due Date Calculator?
Just 2 values: days since your last period started, usual cycle length. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Pregnancy Due Date Calculator work out the answer?
Naegele's rule sets the due date 280 days after the first day of the last menstrual period, adjusted for cycle length. It applies the formula Due date = LMP + 280 days and shows the working so you can check each step by hand.
Is the Pregnancy Due Date Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.