LMP method

Chinese Gender Calendar by LMP

The first day of your last period is usually the one date you know exactly. Enter it below and we estimate your conception date, convert it to the lunar calendar, and read the chart.

Dates from 1900-01-31 to 2101-01-28 are supported. Nothing you type leaves your browser The whole calculation runs on this page.

LMP is a starting point, not the input

The Chinese gender chart is indexed by the lunar month of conception. Your period date is not that, but it is the most reliable date most people have, so it is where pregnancy dating usually begins.

The standard conversion is simple: conception ≈ LMP + 14 days. The calculator above applies it and then does the lunar conversion.

Worked example

A mother born on 15 June 1995, last period starting 24 February 2026:

Add 14 days → estimated conception on 10 March 2026.
Convert to the lunar calendar → lunar month 1.
Her lunar age at that date → 32.
Chart row 32, column 1 → Boy.

See row 32 on the chart, or enter those dates above to reproduce it.

The part most sites skip: your cycle length

The 14-day rule assumes a textbook 28-day cycle. Real cycles vary, and ovulation actually tracks the next period rather than the last one; it tends to fall about 14 days before your next period starts. So on a longer cycle, ovulation is later.

Here is what that does to the same LMP of 24 February 2026:

How cycle length changes the estimated conception date from the same last period
Cycle length	Ovulation on day	Conception	Lunar month
24 days	10	6 Mar	1
26 days	12	8 Mar	1
28 days (assumed)	14	10 Mar	1
30 days	16	12 Mar	1
32 days	18	14 Mar	1
35 days	21	17 Mar	1

In this particular case every cycle length lands in the same lunar month, so the result is stable. That is luck rather than precision; with a different LMP the same spread can straddle a month boundary.

If you know roughly when you ovulated, or you tracked it, enter that date directly with the conception date method instead. It removes the guesswork entirely.

Period dates through 2026, converted

Last period dates in 2026 converted to estimated conception dates and lunar months
First day of last period	Conception date	Lunar month
10 Jan 2026	24 Jan 2026	12
10 Mar 2026	24 Mar 2026	2
10 May 2026	24 May 2026	4
10 Jul 2026	24 Jul 2026	6
10 Sept 2026	24 Sept 2026	8
10 Nov 2026	24 Nov 2026	10

LMP questions

What does LMP mean?

LMP stands for last menstrual period, specifically the first day of it, not the last. It is the date most pregnancy dating starts from, because it is the one date most people can name precisely.

How do you get a conception date from LMP?

The standard assumption is that ovulation happens about 14 days after the first day of your period, so conception is estimated at LMP plus 14 days. That is an assumption based on a 28-day cycle, not a measurement.

What if my cycle is not 28 days?

Then the 14-day rule is wrong for you, and predictably so. Ovulation tends to happen about 14 days before your next period rather than 14 days after the last one. On a 35-day cycle that puts ovulation around day 21, a full week later than the standard assumption, which can move you into a different lunar month.

Is LMP better or worse than using my due date?

They usually agree, because a due date calculated from LMP is just the same assumption carried further. If your due date was revised by an early ultrasound, that revised date is the better input, so use the due date method instead.