Maternity Leave Calculator: Work Out Your Start and End Dates

Quick answer

Statutory Maternity Leave is 52 weeks: you can take it all, and only the first 2 weeks after birth are compulsory. Statutory Maternity Pay covers 39 of those weeks: 90% of your average pay for 6 weeks, then the flat statutory weekly rate (or 90% if lower) for 33 weeks, and the final 13 weeks are unpaid.

Use the maternity leave calculator

Enter your baby's expected due date in the tool above. It works backwards and forwards from that date to show your notification deadline, the earliest start, your default start, and your return-to-work dates for both a six-month and a full twelve-month break. Adjust the start date if you plan to begin earlier and the end dates update with it.

What maternity leave actually covers

Statutory Maternity Leave gives most employees the right to take up to 52 weeks off around the birth of their child. It splits into two halves: the first 26 weeks are Ordinary Maternity Leave and the next 26 weeks are Additional Maternity Leave. You don't have to take the full year, but you're entitled to it from day one of a job, regardless of how long you've worked there or how many hours you do.

Two weeks are compulsory. By law you must take at least two weeks off immediately after the birth (four weeks if you work in a factory). Everything beyond that is your choice, as long as you give the right notice.

One thing this calculator deliberately keeps separate is money. Leave and pay are two different things with two different sets of rules. You can be entitled to 52 weeks of leave but only 39 weeks of Statutory Maternity Pay, and some weeks at the end may be unpaid. To work out the cash side, use our maternity pay calculator alongside this one. Here we focus purely on the dates.

How the maternity leave calculator works

The whole thing pivots on one fixed point: the Expected Week of Childbirth, or EWC. That's the week (running Sunday to Saturday) in which your baby is due. Almost every maternity deadline is measured from the start of that week.

In plain words, the formula is:

• Qualifying week = the 15th week before the week your baby is due. This is the week by which you normally need to be employed and to have notified your employer.
• Notification deadline = the end of that qualifying week. By then you must tell your employer the due date and the date you want your leave to start.
• Earliest start = the start of the 11th week before the week your baby is due. You can't begin Statutory Maternity Leave before this point.
• Latest natural start = the day the baby is born (if it arrives early or you keep working right up to the birth).
• End date = your start date plus up to 52 weeks.

There's also an automatic trigger to watch for. If you're off work for a pregnancy-related reason in the four weeks before your due week, your employer can start your maternity leave from that day, even if you'd planned to work longer. The calculator flags this window so you're not caught out.

The maternity leave calculator does the counting for you, but the logic is simple once you see it: find the due week, step back 15 weeks for the deadline and 11 weeks for the earliest start, then add your leave length to your chosen start date for the return date.

The notice you have to give

You tell your employer by the end of the qualifying week (15 weeks before the due week): your due date and when you want leave to start. Your employer then has 28 days to write back confirming your return date. If you later want to change your start date, you usually need to give 28 days' notice of the new date. To come back early from leave, you must give your employer at least eight weeks' notice of the date you intend to return.

Worked example: Priya, due 12 March 2027

Priya is a primary school teacher whose baby is due on Friday 12 March 2027. She wants to know three things: when she has to tell her head teacher, the earliest she could start, and when she'd be back if she takes the full year.

First, find the Expected Week of Childbirth. The 12th falls in the week running Sunday 7 March to Saturday 13 March 2027. That Sunday is the anchor for everything else.

• Qualifying week (15 weeks before): counting back 15 weeks from the start of the due week lands on the week beginning Sunday 22 November 2026. Priya needs to give notice by the Saturday of that week, 28 November 2026.
• Earliest start (11 weeks before): counting back 11 weeks reaches the week beginning Sunday 20 December 2026. Priya could start her leave as early as Sunday 20 December 2026 if she wanted to.
• Planned start: Priya decides to work on and start her leave on Monday 1 March 2027, the week before her due date.
• Return date (52 weeks later): one year from 1 March 2027 brings her back to work on Monday 1 March 2028.

If Priya instead took only 39 weeks (so she stops once her statutory pay runs out rather than taking unpaid weeks), 39 weeks from 1 March 2027 would bring her back at the end of November 2027. The calculator shows both so she can weigh up a shorter paid break against a longer mostly-unpaid one.

A second scenario: an early arrival

Say the baby comes three weeks early, on 19 February 2027, while Priya is still working. Her maternity leave starts automatically the day after the birth, and her 52 weeks are counted from then, not from her original 1 March plan. Early births are the single biggest reason real return dates differ from the ones people pencil in months ahead, which is why it's worth recalculating once the baby actually arrives.

Keeping in Touch (KIT) days

You're allowed up to 10 Keeping in Touch days during your leave without it ending or losing a week's Statutory Maternity Pay. They're optional on both sides, you can use them for training, a team day or a phased catch-up, and they don't extend or shorten your leave. Use them to make the return smoother rather than to shave time off your year.

Shared Parental Leave: a way to split the time

If you want to share the year with your partner, you can end your maternity leave early and convert the remaining weeks into Shared Parental Leave. Up to 50 weeks of leave and 37 weeks of pay can be split between you, taken in blocks or at the same time. The dates get more involved here, so once you've used this calculator to fix your maternity leave window, treat any Shared Parental Leave plan as a separate exercise with its own notice rules.

Common mistakes and what to watch

• Confusing leave with pay. Leave can run to 52 weeks; Statutory Maternity Pay runs to 39 weeks at most, and the final weeks of leave are often unpaid. Don't assume your return date and your last payday are the same.
• Counting from the due date instead of the due week. The deadlines key off the Sunday-to-Saturday week your baby is due in, not the exact due date. Getting this wrong can shift your notification deadline by several days.
• Missing the 15-week notice deadline. Give notice late and your employer may delay your leave or your pay. Diary the qualifying week as soon as you have a due date.
• Forgetting the automatic early trigger. Pregnancy-related absence in the four weeks before the due week can start your leave for you. If you want to work right up to your due date, factor that risk in.
• Assuming you need a minimum length of service. Statutory Maternity Leave is a day-one right. The qualifying conditions you might be thinking of relate to pay, not leave.
• Overlooking the eight-week early-return notice. If you decide to come back before your planned end date, your employer is entitled to eight weeks' notice. Spring it on them and they can hold you to the original date.

It's also worth checking whether your employer offers an enhanced (contractual) maternity scheme. Many do, with better pay for the first few months, and the eligibility or notice terms can differ from the statutory minimum. Your contract or staff handbook is the place to look.

What to do next

Once you've got your dates, the practical follow-ups are: confirm them in writing with your employer, sort out the money side, and think about your day-to-day budget on a reduced income. Our maternity pay calculator estimates what you'll actually receive each week, and if you're planning around a partner's wage or a phased return, the salary calculator and take-home pay calculator help you see the household figures clearly. If illness rather than pregnancy is keeping you off in the run-up, our statutory sick pay calculator covers that separately.

For the official rules on notice, eligibility and the difference between leave and pay, the government's guide is the authoritative source: gov.uk maternity pay and leave.

This maternity leave calculator gives estimates for guidance only and is not personal employment, tax or financial advice. Check your specific dates and entitlements with your employer or gov.uk before making firm plans.

The 52 weeks, mapped

Official rules and current rates: GOV.UK maternity pay and leave and Maternity Allowance. Returning parents: check Tax-Free Childcare and the benefits checker.