We use cookies.This website uses essential cookies to operate core features. With your consent, we also use analytics cookies to understand traffic and improve the service. For more details, see our .
We use cookies.This website uses essential cookies to operate core features. With your consent, we also use analytics cookies to understand traffic and improve the service. For more details, see our .
Was this tool helpful to use?
Your feedback helps us make it better
A fetal development reference tool based on authoritative consensus, providing standard ranges for key parameters like BPD and head circumference by gestational week.
Replaced with INTERGROWTH-21st 2014 international tables: exact weeks 14–40, mm, P3/P50/P97. Not universal normal ranges or diagnosis. Reference
INTERGROWTH-21st 2014 international reference: exact weeks 14–40, mm, P3/P50/P97. Not a normal range or China expert consensus.
| Gestational Week | Biparietal Diameter (BPD) | Head Circumference (HC) | Abdominal Circumference (AC) | Femur Length (FL) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P3 | P50 | P97 | P3 | P50 | P97 | P3 | P50 | P97 | P3 | P50 | P97 | |
| 14 | 26.3 | 29.6 | 32.9 | 87.4 | 97.9 | 108.4 | 72.9 | 80.6 | 88.4 | 10.3 | 13.1 | 16 |
| 15 | 29.1 | 32.6 | 36 | 99.2 | 110.4 | 121.5 | 82.9 | 91.9 | 100.9 | 13.4 | 16.3 | 19.3 |
| 16 | 32 | 35.7 | 39.3 | 111.1 | 122.9 | 134.7 | 93 | 103.2 | 113.4 | 16.4 | 19.5 | 22.5 |
| 17 | 35 | 38.8 | 42.6 | 123 | 135.4 | 147.8 | 103.1 | 114.4 | 125.7 | 19.4 | 22.5 | 25.7 |
| 18 | 38 | 42 | 45.9 | 134.9 | 147.9 | 160.9 | 113.2 | 125.6 | 138 | 22.3 | 25.5 | 28.7 |
| 19 | 41.1 | 45.2 | 49.3 | 146.8 | 160.3 | 173.8 | 123.3 | 136.7 | 150.1 | 25.2 | 28.5 | 31.7 |
| 20 | 44.1 | 48.4 | 52.8 | 158.5 | 172.5 | 186.5 | 133.4 | 147.7 | 162.1 | 28 | 31.3 | 34.6 |
| 21 | 47.2 | 51.7 | 56.2 | 170.1 | 184.5 | 199 | 143.4 | 158.7 | 174 | 30.6 | 34.1 | 37.5 |
| 22 | 50.3 | 55 | 59.6 | 181.4 | 196.3 | 211.2 | 153.5 | 169.6 | 185.7 | 33.3 | 36.7 | 40.2 |
| 23 | 53.4 | 58.2 | 63 | 192.6 | 207.8 | 223.1 | 163.4 | 180.4 | 197.4 | 35.8 | 39.4 | 42.9 |
| 24 | 56.4 | 61.4 | 66.4 | 203.5 | 219.1 | 234.7 | 173.3 | 191.2 | 209 | 38.3 | 41.9 | 45.5 |
| 25 | 59.4 | 64.5 | 69.7 | 214.1 | 230 | 245.9 | 183.2 | 201.8 | 220.5 | 40.6 | 44.4 | 48.1 |
| 26 | 62.3 | 67.6 | 72.9 | 224.3 | 240.5 | 256.7 | 192.9 | 212.4 | 231.9 | 42.9 | 46.7 | 50.5 |
| 27 | 65.2 | 70.6 | 76 | 234.1 | 250.7 | 267.2 | 202.6 | 222.9 | 243.2 | 45.1 | 49 | 52.9 |
| 28 | 67.9 | 73.5 | 79 | 243.6 | 260.4 | 277.2 | 212.1 | 233.3 | 254.5 | 47.3 | 51.3 | 55.3 |
| 29 | 70.6 | 76.3 | 81.9 | 252.5 | 269.6 | 286.7 | 221.4 | 243.6 | 265.8 | 49.3 | 53.4 | 57.5 |
| 30 | 73.1 | 78.9 | 84.7 | 261 | 278.4 | 295.8 | 230.6 | 253.8 | 277 | 51.3 | 55.5 | 59.7 |
| 31 | 75.5 | 81.4 | 87.3 | 268.9 | 286.6 | 304.4 | 239.6 | 263.9 | 288.3 | 53.2 | 57.5 | 61.9 |
| 32 | 77.8 | 83.8 | 89.8 | 276.3 | 294.4 | 312.5 | 248.4 | 273.9 | 299.5 | 55 | 59.4 | 63.9 |
| 33 | 79.8 | 85.9 | 92 | 283 | 301.5 | 320 | 256.9 | 283.8 | 310.7 | 56.7 | 61.3 | 65.9 |
| 34 | 81.7 | 87.9 | 94.1 | 289.1 | 308.1 | 327.1 | 265.2 | 293.6 | 322 | 58.3 | 63.1 | 67.8 |
| 35 | 83.3 | 89.7 | 96 | 294.5 | 314.1 | 333.6 | 273.2 | 303.3 | 333.4 | 59.8 | 64.8 | 69.7 |
| 36 | 84.7 | 91.2 | 97.7 | 299.2 | 319.4 | 339.6 | 280.8 | 312.8 | 344.9 | 61.3 | 66.4 | 71.5 |
| 37 | 85.9 | 92.5 | 99.2 | 303.1 | 324.1 | 345.1 | 288.1 | 322.3 | 356.4 | 62.6 | 67.9 | 73.3 |
| 38 | 86.7 | 93.6 | 100.5 | 306.1 | 328.1 | 350 | 295.1 | 331.6 | 368.1 | 63.9 | 69.4 | 75 |
| 39 | 87.3 | 94.4 | 101.5 | 308.3 | 331.4 | 354.4 | 301.6 | 340.8 | 379.9 | 65 | 70.8 | 76.6 |
| 40 | 87.5 | 94.9 | 102.3 | 309.6 | 333.9 | 358.3 | 307.7 | 349.8 | 392 | 66.1 | 72.1 | 78.2 |
Indicator Notes
Usage Tips
INTERGROWTH-21st 2014 international reference: exact weeks 14–40, mm, P3/P50/P97. Not a normal range or China expert consensus.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
This reference displays four ultrasound measurements—biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL)—for exact completed gestational weeks from 14+0 through 40+0. Values are in millimeters (mm). Each measurement has three reference points: P3, P50 and P97. The table is a lookup; it does not take a measured value, calculate a percentile, interpolate by pregnancy day or label a result as normal or abnormal.
For example, the row marked week 20 represents 20 weeks + 0 days. Find the measurement named on the ultrasound report, then compare only that same measure and week. A value between P3 and P97 is between those two reference points in this table; that observation alone is not a clinical assessment.
P50 is the middle reference point (the median). P3 and P97 mark the lower and upper reference points shown here. They describe positions in a reference distribution, not a guaranteed healthy interval. BPD means biparietal diameter, HC head circumference, AC abdominal circumference, and FL femur length. The displayed international reference is based on INTERGROWTH-21st standards, developed through a multi-ethnic, population-based project conducted in eight urban areas. It is not a US-specific chart, a Chinese national standard, or a universal diagnostic threshold.
The source project provides separate charts and standards for fetal measurements. This page presents only the four listed measures and three percentile points at exact weeks; it does not show every measure or statistical output in the source materials.
Reference materials: INTERGROWTH-21st fetal growth standards and tools (supports the source standard and fetal growth resources; checked 2026-10-02). INTERGROWTH-21st standards and tools (supports the project's population-based, multi-ethnic, eight-area scope; checked 2026-10-02).
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Use the gestational age recorded for the scan and choose its completed-week row. The table has weekly rows only, ending at 40+0.
Match the report abbreviation to the column group: BPD, HC, AC or FL. Keep the report's measurement name and unit in view.
Read across that measurement's P3, P50 and P97 values. The entries are millimeters. If the report uses centimeters, convert units before comparing: 1 cm equals 10 mm.
Keep the report and the reference values together for a discussion with the clinician who interprets the scan. The table does not calculate an individual percentile or provide a diagnosis.
Use cases
See how the tool fits into real work and everyday tasks.
If a report lists HC and FL at a completed gestational week, locate those two measures in the matching row and note the P3/P50/P97 values. This helps you identify what the reference table displays before asking how the clinical team interprets the full scan.
Bring the scan date, dating method or recorded gestational age, and the original report. You can point to the specific measure and percentile row you are asking about; your clinician can explain whether this reference is appropriate for your circumstances.
Q&A
Find concise answers to common questions and confusing cases.
No. Those are reference percentiles, not a stand-alone health screen. A clinician interprets measurements alongside gestational dating, scan quality, other findings and, when relevant, change over time.
The table lists exact completed weeks only. It has no day-level input or interpolation, so it does not calculate a separate value for 20+4.
Check that you matched the same measurement, gestational age and unit. Reports may use a different reference chart or measurement approach; ask the reporting clinician which chart applies rather than treating this table as a replacement.
Notes
Review scope, result limitations, and important precautions before use.
This table is an educational reference display, not medical advice, a diagnosis, or an individualized assessment of fetal growth. A single measurement or percentile cannot establish whether a fetus is healthy or whether growth is restricted. Interpretation depends on accurate gestational dating, measurement technique, the reference selected by the care team, the pregnancy context and other findings. Professional guidance describes fetal growth assessment as broader than a single size measurement, and serial scans may be relevant to assessing growth over time.
Use the chart only as a discussion aid. If your ultrasound report raises a concern, contact your obstetric care team for an explanation based on your report and clinical history. Do not delay care to compare values here.
Clinical guidance: ISUOG Practice Guidelines: ultrasound assessment of fetal biometry and growth (supports the distinction between a measurement at one time and growth assessment, and the role of clinical context; checked 2026-10-02).
Related
Discover related tools, collections, and available API capabilities.