Health calculator

Pregnancy Week Calculator

Estimate pregnancy week from last menstrual period date. Enter your values below to calculate in the browser and review the formula, example, and cautions on the same page.

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Pregnancy Week Calculator

Enter the values you know. The result updates in your browser and stays separate from the notes and examples.

Use realistic values. Invalid, missing, or impossible inputs will show a friendly warning instead of a broken result.

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ResultEnter values, then calculate.Your output appears here after calculation.
Health estimate: Estimate only. This result is not medical advice and does not replace a clinician, dietitian, trainer, or qualified health professional. Health formulas can miss individual context.

Reviewed estimate context

Health estimate limits

What this result is

Pregnancy Week Calculator gives a browser-calculated estimate from the inputs you enter and the formula displayed on this page.

What can change it

Use the result as a general estimate only. Ask a qualified health professional before changing medication, diagnosis, diet, training, or treatment decisions.

Formula transparency

Formula source type: standard public screening or fitness formula shown on this page. Last review marker: 2026-06-28. Report unclear formulas through the contact page.

Recent results on this device

Calculate once to save a local result on this device.

What is the Pregnancy Week Calculator and Why Does It Matter?

The Pregnancy Week Calculator estimates weeks and days since the last period date. It turns a calendar date into a simple pregnancy timeline.

Picture a long school countdown made of weekly boxes. Each box shows one week passed.

A pregnancy week calculator helps read that timeline without counting every day by hand.

How the Math Works

pregnancy week = days since LMP ÷ 7

SymbolMeaningSimple way to think about it
LMPLast menstrual period dateThe starting calendar day
days since LMPDays passed since that dateThe counted timeline
÷ 7Divide by one weekTurns days into weeks
weekEstimated pregnancy weekThe weekly box number

Example: 70 days since LMP.

  1. Start with 70 days.
  2. Divide 70 by 7.
  3. 70 ÷ 7 = 10.
  4. The estimate is 10 weeks.

Real-Life Examples

Example 1: Kid-friendly use

A class counts weeks until a big school play. The week number shows progress.

Example 2: Everyday adult use

A parent tracks a pregnancy timeline before a doctor visit.

Mistakes to Avoid

Mistake 1: Using today as the start date. The start is the last period date.

Mistake 2: Choosing a future LMP date. That creates a negative timeline.

Zero days means week 0. Huge day counts may be outside normal pregnancy timing.

Frequently Asked Questions

What happens if I enter zero?

Zero days means no full week has passed. The calculator shows the beginning of the timeline.

Why is this easier than doing it by hand?

Counting calendar days is easy to mess up. The tool handles the date math fast.

Can I use this with Pregnancy Due Date Calculator or Due Date Countdown Calculator?

Yes. Pregnancy Due Date Calculator estimates the date. Due Date Countdown Calculator counts remaining days.

FAQ

Is this health result a diagnosis?

No. Health calculators provide general educational estimates and cannot replace a clinician or qualified health professional.

Why can health calculator results vary?

Results depend on entered values, formula assumptions, age, activity, body composition, health context, and individual differences.

What should I check before using this result?

Check the input units, the formula shown on the page, and any assumption that does not match your situation.

What if the result looks off?

Recheck the values and units first. If the formula or label looks wrong, send the page URL and example values through the contact page.

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