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Pregnancy Due Date Calculator

Estimates the due date from your last period, conception date or IVF transfer, with a full week-by-week timeline.

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Enter your figures and press Calculate.
In short Pregnancy Due Date Calculator is a free online tool on inputtesthub.com that estimates the due date from your last period, conception date or IVF transfer, with a full week-by-week timeline. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Pregnancy Due Date Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Pregnancy Due Date Calculator

The Pregnancy Due Date Calculator estimates the due date from your last period, conception date or IVF transfer, with a full week-by-week timeline. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Getting an estimated due date between appointments.
  • Working out which week and trimester you are in today.
  • Planning leave dates around an expected delivery.

The maths behind it

This tool uses Naegele's rule: due date = first day of the last period + 280 days, adjusted for cycle length when it differs from 28 days. Every intermediate value is shown on screen, so the result can be checked by hand.

An estimated due date is a midpoint, not a deadline. Only about 4% of babies arrive on it, and most births happen within two weeks either side. A dating ultrasound is more accurate than any date-based formula.

Frequently asked questions

Are there any usage caps on the Pregnancy Due Date Calculator?
There is no cost and no cap. The Pregnancy Due Date Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Is the Pregnancy Due Date Calculator safe to use with private information?
No. The Pregnancy Due Date Calculator runs entirely in your browser using JavaScript. Because the work happens locally, the tool also keeps working if your connection drops, and closing the tab is all it takes to discard everything.
What formula does the Pregnancy Due Date Calculator use?
It uses Naegele's rule: due date = first day of the last period + 280 days, adjusted for cycle length when it differs from 28 days. The full working is printed under the result, so you can follow every step rather than trusting a black box.
Who is the Pregnancy Due Date Calculator for?
Typical uses: getting an estimated due date between appointments. Working out which week and trimester you are in today. Planning leave dates around an expected delivery. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Any caveats I should know about?
An estimated due date is a midpoint, not a deadline. Only about 4% of babies arrive on it, and most births happen within two weeks either side. A dating ultrasound is more accurate than any date-based formula.
How precise is the result?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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