Pregnancy Calculator.

How the Pregnancy Calculator works.

Pregnancy Calculator example using the starting values.

This Pregnancy Calculator example uses the starting inputs: First day of last menstrual period: 2025-01-01.

Result: 92 weeks

Estimated gestational age from LMP; clinical dating may differ.

What the result means

Estimate gestational age from LMP. The Pregnancy Calculator result describes only the measurements and method shown; it is not a diagnosis or an individualized target.

Enter a consistent scenario

Use Pregnancy Calculator with values from one clearly defined scenario. The visible inputs are first day of last menstrual period. Gestational age is counted from the first day of the last menstrual period, which usually predates conception. It is not confirmation of pregnancy, viability, fetal development, or an individual care plan. Check the unit, period, and meaning of each value before calculating; combining records from different dates can produce a precise-looking but unhelpful answer.

Follow the method

This page applies today − LMP. Gestational age is counted from the first day of the last menstrual period, which usually predates conception. It is not confirmation of pregnancy, viability, fetal development, or an individual care plan. First identify what each entered value represents, convert a percentage to the form required by the displayed formula, and retain intermediate precision. Then make a rough mental check of direction and size. Estimate gestational age from LMP. The worked result is transparent arithmetic rather than an unshown lookup.

Use the result carefully

Read the output as an answer to the narrow question described by the fields, not as a prediction of every real-world outcome. Gestational age is counted from the first day of the last menstrual period, which usually predates conception. It is not confirmation of pregnancy, viability, fetal development, or an individual care plan. For Pregnancy Calculator, compare results only when the measurement basis, time period, currency denomination, or grading convention is the same. This is general information, not a diagnosis, treatment target, or substitute for individual clinical care. Discuss symptoms, pregnancy dating, nutrition, exercise, or a concerning result with a qualified clinician.

Assumptions and boundaries

Before relying on Pregnancy Calculator, identify what its formula—today − LMP—holds constant and what it does not observe. Gestational age is counted from the first day of the last menstrual period, which usually predates conception. It is not confirmation of pregnancy, viability, fetal development, or an individual care plan. Its entries (first day of last menstrual period) define the full scope of this particular result. Do not turn a rounded display into more certainty than the entered data supports; use the official record or provider documentation where it controls.

Common mistakes and next steps

For Pregnancy Calculator, begin a review by comparing the displayed first day of last menstrual period against the source record. Gestational age is counted from the first day of the last menstrual period, which usually predates conception. It is not confirmation of pregnancy, viability, fetal development, or an individual care plan. Typical mistakes are entering a percent as a decimal or vice versa, using an amount from the wrong time period, rounding before the final step, and treating an estimate as an official determination. Record the inputs and result if you need to compare scenarios later.

What the Pregnancy Calculator does not include.

This Pregnancy Calculator result is an estimate, not a diagnosis or treatment plan. Seek urgent care for concerning symptoms and discuss pregnancy, diet, sleep, or activity decisions with a qualified clinician.

Official context and guidance.

• CDC — Pregnancy (opens in a new tab)