How is my due date calculated?
By standard medical convention, a pregnancy due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP).
Tool Categories
Free Pregnancy Due Date Calculator | 1ClickTools
Calculate your estimated pregnancy due date, conception date, and current trimester based on your Last Menstrual Period (LMP). Fast, free, and accurate.
Frequently Asked Questions
Why does cycle length matter?
If your cycle is longer than 28 days, ovulation (and therefore conception) likely happened later in the month. Adjusting your cycle length fixes this discrepancy for a more accurate due date.
Is this calculation 100% accurate?
No due date calculator is 100% accurate. Only about 4% of babies are actually born on their exact estimated due date. It is a helpful baseline, but you should always consult your OB-GYN.
How accurate is this pregnancy calculator tool?
All processing runs entirely in your browser using verified algorithms. Results are computed with full double-precision — no server-side rounding or data transmission occurs.
Is this Pregnancy Due Date Calculator free to use for commercial and personal projects?
Yes, 1ClickTools provides completely free, unlimited access to the Pregnancy Due Date Calculator for both personal and commercial projects. There are no registration forms, hidden fees, software downloads, or monthly subscription limits.