Pregnancy calculator
Estimate weeks pregnant and trimester from LMP or conception date.
What this calculator covers
Use this calculator to estimate gestational age from either the last menstrual period or a known conception date. It keeps the current week, trimester, and due-date context on the same screen so the timeline is easier to audit.
Pregnancy timing calculators are useful for rough planning, but they do not replace clinical dating. If the exact week matters for treatment or care decisions, use the result as a starting point for a clinician conversation rather than the final word.
Frequently asked questions
- What is the difference between LMP and conception as a starting point?
- LMP (last menstrual period) is the standard obstetric reference because it is an easily recalled date. When conception date is used instead, the calculator adjusts the obstetric timeline internally — conception is typically assumed to occur about 14 days after LMP, so gestational age from conception appears roughly two weeks less than the equivalent LMP-based figure.
- How are trimesters defined here?
- The calculator maps weeks 1–12 to the first trimester, weeks 13–27 to the second trimester, and week 28 onward to the third trimester. These are common clinical boundaries, though some sources use slightly different cutoffs.
- Why might my clinician's estimate differ from this result?
- Clinical dating often relies on an early ultrasound, which can measure the embryo directly and refine the due date more accurately than calendar math alone. LMP-based estimates assume a textbook cycle length and ovulation timing that may not match your actual cycle.
- Can I use a past date for the as-of field?
- Yes. You can enter any past or current date in the as-of field to see what the gestational age was at a specific point in time, which is useful for reviewing a timeline or comparing notes from a previous appointment.
Tool
Run the calculation
Result
RESULT · PREGNANCY AGE
â„–144
Primary result
13 weeks, 0 days (Trimester 2)
As of Apr 19, 2026, the conception date timeline shows 13 weeks, 0 days, placing the pregnancy in Week 14 and trimester 2.
- Gestational age
- 13 weeks, 0 days
- Current week
- Week 14
- Trimester
- Trimester 2
- Estimated due date
- Oct 25, 2026
Step-by-step solution
- 1.Start from the selected conception date of Feb 1, 2026.
- 2.Measure the gestational timeline forward to the as-of date of Apr 19, 2026.
- 3.Translate that span into 13 weeks, 0 days, then map the result to Week 14 and trimester 2.
Walkthrough
Visual walkthrough
Pregnancy age is just calendar distance on the obstetric timeline, then trimmed into weeks, days, and trimester bands.
01
Lock the reference date
Feb 1, 2026
The timeline begins from either LMP or conception, depending on the method selected in the form.
02
Measure the gestational span
13 weeks, 0 days
The as-of date determines how many completed weeks and leftover days have elapsed on the obstetric timeline.
03
Assign the current band
The current week and trimester are labels layered on top of that measured gestational age.
Week 14 · Trimester 2