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Next period date calculator

Estimate the dates of your next three periods from your last period and cycle length.

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Due date calculatorEstimate your baby's due date (Naegele's rule).Conception date calculatorEstimate the likely conception date from a due date.IVF Due Date CalculatorDate an IVF pregnancy from the transfer date and the embryo's age, with gestational age today, the trimester and term milestones, and the equivalent LMP date.Ovulation calculatorFind your fertile window from your last period.Pregnancy week calculatorFind your current pregnancy week and trimester from your last period.Baby Growth Percentile CalculatorWeight, length and head circumference percentiles from the WHO Child Growth Standards, 0-24 months.Baby Milk Intake CalculatorBottle volumes per feed and per day by your baby's weight and age, with the feeding interval.Gestational Age CalculatorGestational age in weeks and days from your LMP, due date or conception date, with trimester and EDD.

Need Next period, Following period, Third period? The Next period date calculator derives it from First day of last period, Average cycle length (days) in one step. For instance, with First day of last period = 1985-03-20 and Average cycle length (days) = 28 it returns Next period = 17/04/1985, Following period = 15/05/1985 and Third period = 12/06/1985.

How to use it

  1. Enter your values: First day of last period, Average cycle length (days).
  2. Read the result instantly: Next period, Following period, Third period.

Frequently asked questions

How does the Next period date calculator work?

It takes First day of last period and Average cycle length (days) and derives Next period, Following period and Third period from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: First day of last period and Average cycle length (days). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With First day of last period = 1985-03-20 and Average cycle length (days) = 28, the calculator returns Next period = 17/04/1985, Following period = 15/05/1985 and Third period = 12/06/1985. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

When would I actually use this?

Placing a pregnancy on the calendar: the estimated due date, the current week, and when the usual appointments and screenings fall.

What is the most common mistake?

Reading the due date as a deadline. It is a median: fewer than one birth in twenty happens on it, and a normal term spans several weeks around it.

What is the difference between the Next period date calculator and the Due date calculator?

This one returns Next period and Following period; the Due date calculator returns Estimated due date and Estimated conception. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Conception date calculator is the closest one after this: Estimate the likely conception date from a due date.

What else is worth having open alongside it?

IVF Due Date Calculator and Ovulation calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from, and how current are they?

Dating follows Naegele's rule (280 days from the last period) or the transfer date for assisted conception. An early ultrasound is more accurate than any calculation and takes precedence over it.

Further reading

All guides →
How-toHow to Predict Your Next Period (And How Far Off the Estimate Can Be)Add your average cycle length to the first day of your last period. Here is how to measure that length properly, why the estimate has a range rather than a date, and when irregularity is worth a consultation.ExplainerWhat Is a Normal Menstrual Cycle Length? The Numbers, by Life StageFIGO puts a normal cycle at 24 to 38 days; ACOG's older range is 21 to 35. Here is why two respected bodies give different numbers, how much variation is normal, and how cycles change after menarche and before menopause.ExplainerIVF Dating Is the One Case Where the Date Is Actually KnownEvery other pregnancy is dated from an estimate. After IVF, fertilisation is timed to the hour, so gestational age is arithmetic: 266 days from fertilisation, minus the embryo's age at transfer. Here is the derivation for day-3, day-5 and day-6 embryos, why frozen and fresh transfers use the same rule, why an early scan rarely moves an IVF date, and what the two-week offset on a scan report means.How-toHow to Calculate Your Due DateNaegele's rule adds 280 days to your last period — or subtract three months and add seven days. Here's how it works and why it's only an estimate.ExplainerHow Much Milk Does a Baby Need? The Rule of Thumb and Its LimitsA formula-fed baby takes roughly 2.3 fl oz per pound of body weight per day in the first months, split across the day's feeds. Here is the table by age and weight, why breastfed babies are not measured this way, and the signs that outrank any number.GuidePregnancy Week by Week: The Calendar and What Each Stage MeansPregnancy is counted in 40 weeks from your last period, not from conception — so you are already two weeks pregnant at conception. Here is the full calendar, the trimester boundaries and what term actually means.