Morning Sickness Calculator

Where this date falls —

Pregnancy age on that date: —
Weeks pregnant (decimal): —
Usual onset (week 6): —
Usual peak (weeks 8–12): —
Most ease by (weeks 16–20): —
Days until week 20: —

Pregnancy week against the usual nausea timeline

The chart appears with your result

Pregnancy nausea usually starts around week 6, is worst between weeks 8 and 12, and for most people improves by weeks 16 to 20, all counted from the first day of the last period. With a last period on 1 January 2026, onset would be around 12 February and week 20 falls on 21 May.

About this tool

Nausea and vomiting affect most pregnancies in the first trimester, and the question people ask most is how long it will last. This calculator turns the first day of your last period into a pregnancy age on any date you pick, then places that date on the usual timeline: onset around week 6, the peak stretch of weeks 8 to 12, and the weeks 16 to 20 by which most people feel better. It lists the calendar dates for each stage, counts the days left until week 20, and marks your week on a scale chart that you can download as PNG, SVG or CSV. The timeline is a population pattern, not a forecast for one person: some never feel sick, some feel better by week 12, and roughly one in ten still has symptoms after week 20.

How to use it

Enter your last period
Pick the first day of your last menstrual period. If a dating scan moved your due date, use the period date that matches the scan.
Choose the date to check
Usually today, or any future date you want to plan around, such as a trip or a return to work.
Read the stage and dates
The headline names the stage that date falls in; the onset, peak and easing dates and the days left until week 20 are listed below, with the working.
Check the scale
The chart shows your week against the onset, peak and easing bands.

Examples

Last period 1 Jan, checked 12 Mar

First day of last period: 2026-01-01
Date to check: 2026-03-12

Result Where this date falls: Usual peak window
Pregnancy age on that date: 10 weeks 0 days
Weeks pregnant (decimal): 10
Usual onset (week 6): 12 Feb 2026
Usual peak (weeks 8–12): 26 Feb 2026 – 25 Mar 2026
Most ease by (weeks 16–20): 23 Apr 2026 – 21 May 2026
Days until week 20: 70

Days since last period = 70 → 10 weeks 0 days
Usual onset (week 6) = LMP + 42 days = 12 Feb 2026
Usual peak (weeks 8–12) = LMP + 56 to 83 days = 26 Feb 2026 to 25 Mar 2026
Usual easing (weeks 16–20) = LMP + 112 to 140 days = 23 Apr 2026 to 21 May 2026

Seventy days after the last period is exactly 10 weeks, the middle of the stretch when nausea is usually at its worst. Week 20 falls on 21 May.

Last period 1 Jan, checked 29 Jan

First day of last period: 2026-01-01
Date to check: 2026-01-29

Result Where this date falls: Before the usual onset
Pregnancy age on that date: 4 weeks 0 days
Weeks pregnant (decimal): 4
Usual onset (week 6): 12 Feb 2026
Usual peak (weeks 8–12): 26 Feb 2026 – 25 Mar 2026
Most ease by (weeks 16–20): 23 Apr 2026 – 21 May 2026
Days until week 20: 112

Days since last period = 28 → 4 weeks 0 days
Usual onset (week 6) = LMP + 42 days = 12 Feb 2026
Usual peak (weeks 8–12) = LMP + 56 to 83 days = 26 Feb 2026 to 25 Mar 2026
Usual easing (weeks 16–20) = LMP + 112 to 140 days = 23 Apr 2026 to 21 May 2026

At 4 weeks most people have no nausea yet; the usual onset around week 6 would be 12 February.

Last period 1 Jan, checked 1 Jun

First day of last period: 2026-01-01
Date to check: 2026-06-01

Result Where this date falls: Past the usual easing point
Pregnancy age on that date: 21 weeks 4 days
Weeks pregnant (decimal): 21.6
Usual onset (week 6): 12 Feb 2026
Usual peak (weeks 8–12): 26 Feb 2026 – 25 Mar 2026
Most ease by (weeks 16–20): 23 Apr 2026 – 21 May 2026
Days until week 20: 0

Days since last period = 151 → 21 weeks 4 days
Usual onset (week 6) = LMP + 42 days = 12 Feb 2026
Usual peak (weeks 8–12) = LMP + 56 to 83 days = 26 Feb 2026 to 25 Mar 2026
Usual easing (weeks 16–20) = LMP + 112 to 140 days = 23 Apr 2026 to 21 May 2026

At 21 weeks 4 days the usual easing point has passed, so ongoing sickness is flagged as worth discussing with a midwife or doctor.

How it is calculated

Pregnancy age = check date − LMP; stage dates = LMP + 42, 56–83 and 112–140 days

LMP: First day of the last menstrual period
42 days: Week 6, the usual onset of nausea
56–83 days: Weeks 8 to 12, when symptoms usually peak
112–140 days: Weeks 16 to 20, by which most people improve

Obstetric dating counts pregnancy from the first day of the last period, so week 6 is 42 days after it. The tool counts the days between that date and the date you choose, splits them into whole weeks and days, and compares the total with the stage boundaries described by the NHS and ACOG. Each stage date is the LMP plus a fixed number of days, so the dates shift exactly with your period date.

Sources

Vomiting and morning sickness — NHS
Morning Sickness: Nausea and Vomiting of Pregnancy — ACOG
Morning Sickness — Cleveland Clinic

When not to use it

Do not use it to judge whether vomiting is severe enough to need treatment.
It is not a pregnancy test and cannot confirm a pregnancy.
After IVF transfer, date from the clinic's equivalent LMP rather than the transfer day.

Common mistakes

Entering the conception date instead of the first day of the last period, which shifts every stage by about two weeks.
Reading week 20 as a deadline; some people improve earlier and some later.
Using the last day of the period rather than the first day.

Frequently asked questions

When does morning sickness usually start?

Most people notice it around week 6 of pregnancy, counted from the first day of the last period, and ACOG notes it usually begins before week 9. That is roughly two weeks after a missed period for someone with a 28-day cycle.

When is morning sickness at its worst?

Symptoms commonly peak between weeks 8 and 12. This matches the rise of the pregnancy hormone hCG, which reaches its highest level near the end of the first trimester, though the exact cause of the nausea is not fully understood.

When does morning sickness stop?

The NHS says that for most people it improves or stops by around weeks 16 to 20. A minority keep some nausea for longer, and a small number feel unwell for most of the pregnancy.

Why is it called morning sickness if it lasts all day?

The name is historical. Nausea can come at any time of day or night, and many people feel worst in the late afternoon or when their stomach is empty.

What is hyperemesis gravidarum?

It is a severe form of pregnancy sickness with persistent vomiting, dehydration and weight loss, affecting around 1 to 3 in 100 pregnancies. Being unable to keep fluids down for 24 hours, very dark urine or feeling faint are signs to contact a midwife, doctor or maternity unit promptly.

Does having no morning sickness mean something is wrong?

No. A sizeable share of pregnancies have little or no nausea, and its absence on its own is not a sign of a problem. Sudden loss of symptoms alongside pain or bleeding is different and should be checked.

Why does the tool count from my last period rather than conception?

Clinics and scan reports date pregnancy from the first day of the last period, and the published stage weeks use the same count. Conception usually happens about two weeks after that date.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 25). Morning Sickness Calculator. Tools Directory. Retrieved October 28, 2026, from https://tools.milunir.com/health/medical-reference/morning-sickness-calculator/

MLA

Tools Directory Editorial Team. “Morning Sickness Calculator.” Tools Directory, 25 Oct. 2026, https://tools.milunir.com/health/medical-reference/morning-sickness-calculator/. Accessed 28 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Morning Sickness Calculator.” Tools Directory. Last modified October 25, 2026. Accessed October 28, 2026. https://tools.milunir.com/health/medical-reference/morning-sickness-calculator/.

Link

<a href="https://tools.milunir.com/health/medical-reference/morning-sickness-calculator/">Morning Sickness Calculator – Tools Directory</a>