Life Fertility Clinic Sydney
Find your estimated due date
Whether you're expecting naturally or through IVF, estimate your due date and see how far along you are today.
If your cycle is longer or shorter than 28 days, this helps refine your estimate.
Use this if you know roughly when ovulation or conception occurred.
Estimated due date
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—This calculator gives an estimate only — only around 5% of babies arrive on their exact due date. Your care team will confirm your dates with an early scan. This tool doesn't replace personalised medical advice.
Due Date Calculator
How our due date calculator works
Your due date is an estimate, not a guarantee. Most pregnancy calculators use one of three starting points, and this tool lets you choose whichever applies to you.
If you know the first day of your last period (LMP), we estimate a 280-day pregnancy from that date, adjusted for your average cycle length if it's longer or shorter than 28 days. This is the standard method used for naturally conceived pregnancies and is based on ovulation typically occurring around day 14 of a 28-day cycle.’
If you conceived through IVF, your due date is calculated from your embryo transfer date and the age of the embryo at transfer, since this gives a more precise starting point than LMP alone. Day 3, Day 5 (blastocyst), and Day 6 (blastocyst) embryo transfers each use a different offset, because the embryo's age at transfer tells us how many days of development have already occurred before it was placed.
Calculating your due date from a known conception date
If you know roughly when conception occurred, rather than your last period or an IVF transfer date, you can estimate your due date directly from that date. This is common for people tracking ovulation closely, or for pregnancies conceived with the help of fertility drugs or IUI (intrauterine insemination), where the approximate timing of conception is known.
This method estimates a 266-day pregnancy from the conception date itself, compared with 280 days from the first day of your last period. The difference reflects the roughly two weeks between the start of your last period and ovulation in a typical cycle. If you're not sure of your exact conception date, the last period or IVF transfer methods will usually give a more reliable estimate, since they're based on a firmer reference point.
Why your due date might change
An early dating scan, usually done between 8 and 13 weeks, is the most accurate way to confirm your due date. Ultrasound measurements at this stage can be more precise than calculations based on LMP alone, particularly if your cycle is irregular. Your care team may adjust your estimated due date after this scan.
A note on accuracy
Only a small proportion of babies are born on their exact estimated due date. Most births happen within a window of a couple of weeks on either side. This calculator is a starting point for your pregnancy planning, not a clinical diagnosis or a substitute for advice from your fertility specialist or obstetrician.
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A due date calculator gives an estimate based on standard pregnancy length averages. It's a useful planning tool, but only a small percentage of babies arrive on their exact calculated date. Your care team will refine this estimate using an early dating scan.
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Calculating from your last menstrual period (LMP) assumes ovulation occurred around two weeks later, which is an estimate. Calculating from a known conception date removes that guesswork, so it can be a more direct estimate if you know roughly when conception occurred.
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Your due date is calculated from your embryo transfer date, adjusted for the embryo's age at transfer. Because IVF removes the uncertainty around ovulation timing, this method is generally considered more precise than an LMP-based estimate for naturally conceived pregnancies. -
Yes. Each embryo age at transfer reflects a different stage of development, so the calculation from transfer date differs between them. A Day 5 or Day 6 blastocyst has developed further than a Day 3 embryo before transfer. Select the correct embryo age at transfer for an accurate estimate.
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Most due date calculations work backwards or forwards from a known reference point, whether that's the first day of your last period, a known conception date, or an IVF embryo transfer date. Each method estimates a due date roughly 40 weeks (280 days) from the start of pregnancy, adjusted depending on which reference point you're using and how far along development was at that point.
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You can, but the estimate will be less precise the less certain you are of the actual date. If you track ovulation closely or know roughly when you conceived, this method works well. If you're unsure, using your last period or IVF transfer date (if applicable) will generally give a more reliable estimate, since those are fixed, known dates.
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The standard due date calculation assumes a 28-day cycle with ovulation around day 14. If your average cycle is longer or shorter, adjusting for this helps refine the estimate of when ovulation and conception likely occurred.
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It can. An early dating scan is generally considered more accurate than a calculation based on LMP alone, especially if your cycles are irregular. Your fertility specialist or obstetrician may update your estimated due date based on scan measurements.