Fetal Size by Week Reference
Median length and weight at each gestational week — the fruit-comparison chart with actual numbers.
These are medians — healthy babies at any week span a wide percentile range, and your scan's percentile (not the absolute grams) is what your provider tracks. The growth story is exponential: weight triples between 28 and 40 weeks, which is why the last trimester eats the energy budget.
Formula
For general information only. Pregnancy and infant care decisions must be guided by your treating clinician or midwife — always defer to their assessment.
Median length and weight at each gestational week — the fruit-comparison chart with actual numbers. The Fetal Size by Week Reference is a free, private fetal size by week tool — every result computes instantly in your browser with no sign-up and no data upload.
About Fetal Size by Week Reference
These are medians — healthy babies at any week span a wide percentile range, and your scan's percentile (not the absolute grams) is what your provider tracks. It applies medians from INTERGROWTH-21st / WHO fetal growth charts. Use the Fetal Size by Week Reference to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Fetal Size by Week Reference
- 1Enter your details in the Fetal Size by Week Reference input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Fetal Size by Week Reference?
- ✓Instant fetal size by week result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Papageorghiou AT et al., Lancet 2014 — INTERGROWTH-21st standards)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Fetal Size by Week Reference work?+
These are medians — healthy babies at any week span a wide percentile range, and your scan's percentile (not the absolute grams) is what your provider tracks. The calculation uses the formula: medians from INTERGROWTH-21st / WHO fetal growth charts. Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Fetal Size by Week Reference accurate, and what is it based on?+
The method is traceable to authoritative sources: Papageorghiou AT et al., Lancet 2014 — INTERGROWTH-21st standards. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Fetal Size by Week Reference free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is informational only. Always defer to your treating clinician or midwife for pregnancy and infant care decisions.
What can I use the Fetal Size by Week Reference for?+
It's commonly used for fetal size by week, baby size week, fetus weight chart. Median length and weight at each gestational week — the fruit-comparison chart with actual numbers.
Related Health tools
Adult BMI Calculator (WHO)
Body-mass index for adults with the WHO reference bands shown neutrally, plus the substituted formula step by step.
● LiveBMI Calculator (lb & inches)
US-style BMI from pounds and inches using the ×703 conversion, with CDC adult reference ranges.
● LiveBMI Calculator for Women
BMI with reference context written for women — what the index can and cannot say about female body composition.
● Live