Last verified: August 2026 · Methodology
Gestational Age Calculator
Last verified: September 2026
This free gestational age calculator is also ChronoCalc’s PMA calculator: enter gestational age at birth, date of birth, and a target date to get post menstrual age (PMA), weeks of prematurity, and related clocks. Educational aid only—not medical advice.
NICU Age Details
NICU Age Results
Post-Menstrual Age (PMA)
Corrected Gestational Age
Chronological Age
Weeks of Prematurity
Corrected Age (for follow-up)
Enter gestational age and dates to calculate PMA
NICU Standard
PMA-style addition
PMA + Corrected Age
Dual output format
Runs locally
No data transmission
Print Reports
For study notes
Educational note — not medical advice
This tool computes PMA-style addition (gestational age plus chronological age) for learning and note practice. For post-discharge developmental follow-up in months, switch to our corrected age calculator. Label which clock you mean in any chart. Confirm protocols with the care team and published guidance from sources such as the CDC and AAP Publications.
What this gestational age calculator is
This gestational age calculator is ChronoCalc’s live tool for NICU-style age clocks. It is free, runs in your browser, and does not send dates to a server.
People searching for a pma calculator land here on purpose. There is no third tool URL for PMA. Post menstrual age is an output of this gestational age calculator.
Use it to practice labeling PMA, chronological age, weeks early, and a follow-up corrected-age estimate. It does not diagnose, prescribe, or replace a neonatal chart.
Families, nursing students, and new NICU staff often need one quiet place to see how the weeks add up. This gestational age calculator is that practice surface.
How to use this gestational age calculator
Open the form above. Enter gestational age at birth in weeks (decimals allowed for leftover days). Then enter date of birth and an optional target date.
Press Calculate. The gestational age calculator returns PMA in weeks, a weeks-and-days detail line, chronological age, weeks of prematurity, and a corrected-age style follow-up line.
Copy or print only after you confirm the gestational age matches the medical record. Wrong GA in means wrong PMA out—even when the calendar math is perfect.
Method notes live on our methodology page. Everyday birthday age without prematurity lives on the chronological age calculator.
If you are comparing notes with a classmate, agree on the same target date before you blame the gestational age calculator for a one-day mismatch.
What is post menstrual age (PMA)?
Post menstrual age (PMA) is gestational age at birth plus chronological time since birth. NICUs speak this clock in weeks and days.
Example: born at 32 weeks, now 4 weeks old chronologically → PMA about 36 weeks. At 8 weeks old, PMA is about 40 weeks—term equivalence on that clock.
A pma calculator is not a separate product here. This gestational age calculator is the pma calculator Google Search Console should associate with PMA queries.
Read the short primer PMA meaning in the NICU if you only need definitions before you run numbers.
When a note says “corrected gestational age” in weeks during the NICU stay, it often means the same sum your gestational age calculator just printed as PMA.
The PMA formula this gestational age calculator uses
The core formula is simple addition:
Chronological weeks come from exact calendar days between birth and the target date, divided by seven. The gestational age calculator then formats leftover fractional weeks as days.
Gestational age usually comes from first-trimester ultrasound when available. Without ultrasound, teams may use last menstrual period dating. Enter whatever GA the chart uses so your practice note matches the unit’s language.
For a hand-worked walkthrough, see how to calculate PMA, then check the same dates on this gestational age calculator.
Leap days matter when the interval crosses February 29. Let the gestational age calculator handle the calendar instead of napkin math that forgets a day.
Corrected gestational age vs PMA
In many NICU notes, corrected gestational age and PMA describe the same sum. Teams use both labels for gestational age plus days of life.
After discharge, “corrected age” often means chronological age minus weeks of prematurity, written in months for milestones. That outpatient clock is why we keep a separate adjusted / corrected age calculator.
This gestational age calculator shows both styles so you can see why labels matter. Always write the unit (weeks vs months) next to the number.
Longer naming pitfalls are covered in the CGA naming case study and the corrected age guide.
If a referral form asks for “adjusted age,” do not paste PMA weeks from the gestational age calculator without converting clocks.
How NICUs use numbers from a gestational age calculator
Accurate PMA labeling supports shared language across nursing notes, neonatology rounds, and research screens. A gestational age calculator helps keep that language consistent during training.
Feeding advancement discussions often reference PMA bands rather than birthday age alone. Respiratory support weans are likewise discussed against post menstrual age milestones in many units.
Screening calendars—such as for retinopathy of prematurity—are typically scheduled by PMA windows defined in clinical protocols, not by a public web tool. Use this gestational age calculator only to understand the arithmetic behind those calendars.
Vaccine timing, developmental exams, and discharge conversations also mix chronological age and PMA. Label every number so the next clinician does not assume the wrong clock.
None of those workflows should treat ChronoCalc as the order set. The gestational age calculator is a learning mirror for the arithmetic only.
Prematurity categories by gestational age
Categories below are common educational groupings. They are not a diagnosis from ChronoCalc or any consumer tool.
| Category | Gestational Age | Notes |
|---|---|---|
| Extremely preterm | < 28 weeks | Highest support needs typical |
| Very preterm | 28 to < 32 weeks | Often prolonged NICU course |
| Moderate preterm | 32 to < 34 weeks | Variable course |
| Late preterm | 34 to < 37 weeks | Still may need monitoring |
| Term | 37 to 42 weeks | Baseline comparison band |
Public overviews of preterm birth risk and infant health appear on the CDC site. Professional statements and journal material appear through AAP Publications.
Worked example with this gestational age calculator
Suppose birth is 15 March 2025 at 30.0 weeks gestation. The target date is 3 June 2025. Chronological age is about 11 weeks 5 days.
PMA ≈ 30 + 11.7 ≈ 41.7 weeks. The infant has passed term equivalence on the post menstrual age clock. That is the number many NICU discussions would emphasize at that moment.
Run the same inputs in the gestational age calculator above and compare your hand math. If they disagree, check leap days, time zones on date inputs, and whether GA was entered as weeks+days correctly.
Birthday age alone is a different question. Use the chronological age calculator when a form wants years, months, and days without prematurity adjustment.
PMA calculator vs chronological age
Chronological age starts at birth. PMA starts from the pregnancy dating clock and keeps ticking after birth. A pma calculator answers the second clock.
School forms, passports, and most vaccines use chronological age. NICU feeding and ROP calendars often use post menstrual age. Mixing them without labels causes chart confusion.
This gestational age calculator prints both clocks so trainees can see the gap. It still will not tell you which protocol applies—that comes from the care team.
When GSC shows impressions for “pma calculator,” this gestational age calculator page is the intended ranking URL. Do not invent a duplicate /pma slug.
Input quality tips for the gestational age calculator
Prefer the gestational age documented on admission or discharge summaries. Do not average conflicting notes without asking the team which dating method the unit uses.
Enter fractional weeks carefully. Three days past 32 weeks is often written 32+3, which is about 32.4 in decimal weeks (3÷7).
Target date should match the note you are writing—today for a current note, or the exam date for a historical summary. The gestational age calculator defaults the target to today for convenience.
If birth date is after the target date, the tool blocks the run. Fix the dates rather than forcing a negative age.
What each gestational age calculator output means
PMA weeks is the primary NICU-style total. The detail line shows completed weeks and leftover days.
Corrected gestational age on the result card restates the same addition in a sentence so the formula is visible. It is not a second secret algorithm.
Chronological age is birthday age in years, months, and days plus weeks. Use it when comparing to non-NICU clocks.
Weeks of prematurity uses 40 minus gestational age at birth (floored at zero for term or later). It feeds the follow-up corrected-age estimate.
Corrected age (for follow-up) subtracts those early weeks from chronological time. For dedicated outpatient workflows, prefer the corrected age calculator.
Documenting PMA and related clocks
Write the clock name next to every number: “PMA 36w 2d,” not just “36 weeks.” Ambiguous weeks invite the wrong protocol.
Include gestational age at birth and the dates used. A future reader should rebuild your run without guessing which day you meant.
Print or copy features are for study notes and drafts. Final clinical documentation belongs in the official record under institutional policy.
If your unit uses CGA as a synonym for PMA, say so once in the note. Naming drift is a common handoff error between NICU and clinic.
Common mistakes with a gestational age calculator
Entering estimated due date instead of gestational age at birth breaks the formula. This gestational age calculator expects GA weeks, not EDD.
Using months for chronological age inside a weeks formula also breaks results. Convert calendar days to weeks, or let the tool do it from dates.
Stopping PMA language the day after discharge without switching to corrected age months can confuse early intervention teams. Know which clock the referral form wants.
Treating any consumer web tool as a screening order is unsafe. Screening windows come from clinicians and published guidelines, not from ChronoCalc.
Parents, students, and PMA language
Parents often search PMA after a NICU tour. This page can explain why nurses talk in weeks that look “older” than birthday age.
It cannot interpret growth charts, feeding plans, or prognosis. Ask the care team those questions. Public reading lists from the CDC are a better starting point for general prematurity education.
Nursing and medical students can use the pma calculator mode here to check homework arithmetic. Always cross-check against the course’s required rounding rules.
Speech-language pathologists working with former preemies usually need corrected age in months for early intervention—not PMA weeks. Link out to the adjusted tool when that is the form’s language.
Related ChronoCalc reading
PMA definition: PMA meaning in the NICU. Hand arithmetic: how to calculate PMA.
Clock naming: CGA naming case study. Outpatient correction: corrected age guide.
Cluster overview: chronological, corrected, and adjusted age. Method changelog: methodology.
Every path above should still point readers who need a live run back to this gestational age calculator for PMA and to the adjusted page for month-based correction.
Privacy on this page
Dates stay in the browser session. ChronoCalc does not require an account to run the form.
Do not paste identifiable patient names into copied text you share outside secure systems. Treat printouts like any other draft with dates of birth.
HIPAA compliance is about your organization’s workflows, not a marketing badge on a calculator. Use institutional tools for official charting.
Limitations of the tool
The tool accepts GA between 20 and 44 weeks. Extreme outliers need manual clinical systems, not this educational helper.
It does not adjust for IVF dating quirks beyond whatever GA you type. Enter the GA your unit already decided to use.
Fractional week display rounds leftover days for readability. For legal or research datasets, follow the study’s specified rounding—not a blog helper.
Last verified September 2026. If a publisher or unit changes a labeling convention, update your notes; this page tracks ChronoCalc’s educational math only.
Educational disclaimer
ChronoCalc’s gestational age calculator is an educational aid for understanding PMA, post menstrual age labeling, and related clocks. It is not medical advice.
Do not use it alone to schedule screens, change feeds, or make discharge decisions. Those choices belong to licensed clinicians following institutional protocols.
External links to the CDC and AAP Publications are for general reference. They do not imply endorsement of ChronoCalc by those organizations.
Related age calculation tools
Need PMA weeks? Stay on this gestational age calculator. Need outpatient corrected months? Use the adjusted tool. Need birthday Y;M;D? Use home.