Estimated Fetal Weight Calculator (Hadlock)
EFW from the scan's AC and FL measurements via the Hadlock equation your sonographer's machine uses.
Every ultrasound weight estimate carries ±10–15% error — at term that's ±500 g, which is why 'they said 3.8 kg' babies arrive at 3.3 all the time. Hadlock's 1985 equations remain the global default; your report's EFW (using AC+FL±BPD±HC variants) is the authoritative one. Big- or small-sounding estimates change plans only via your obstetrician.
Formula
Reference aid for healthcare professionals only. Every result must be independently verified before clinical use. Never use this tool for self-medication or to replace clinical judgement.
EFW from the scan's AC and FL measurements via the Hadlock equation your sonographer's machine uses. The Estimated Fetal Weight Calculator (Hadlock) is a free, private fetal weight calculator tool — every result computes instantly in your browser with no sign-up and no data upload.
About Estimated Fetal Weight Calculator (Hadlock)
Every ultrasound weight estimate carries ±10–15% error — at term that's ±500 g, which is why 'they said 3.8 kg' babies arrive at 3.3 all the time. It applies log₁₀(EFW) = 1.304 + 0.05281·AC + 0.1938·FL − 0.004·AC·FL (cm). Use the Estimated Fetal Weight Calculator (Hadlock) 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 Estimated Fetal Weight Calculator (Hadlock)
- 1Enter your details in the Estimated Fetal Weight Calculator (Hadlock) 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 Estimated Fetal Weight Calculator (Hadlock)?
- ✓Instant fetal weight calculator 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 (Hadlock FP et al., Am J Obstet Gynecol 1985 — fetal weight estimation)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Estimated Fetal Weight Calculator (Hadlock) work?+
Every ultrasound weight estimate carries ±10–15% error — at term that's ±500 g, which is why 'they said 3.8 kg' babies arrive at 3.3 all the time. The calculation uses the formula: log₁₀(EFW) = 1.304 + 0.05281·AC + 0.1938·FL − 0.004·AC·FL (cm). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Estimated Fetal Weight Calculator (Hadlock) accurate, and what is it based on?+
The method is traceable to authoritative sources: Hadlock FP et al., Am J Obstet Gynecol 1985 — fetal weight estimation. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Estimated Fetal Weight Calculator (Hadlock) 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 is a reference aid for healthcare professionals and must be independently verified. It is not for self-diagnosis or self-medication.
What can I use the Estimated Fetal Weight Calculator (Hadlock) for?+
It's commonly used for fetal weight calculator, hadlock formula, efw calculator. EFW from the scan's AC and FL measurements via the Hadlock equation your sonographer's machine uses.
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