NHS Pregnancy Calculator 2026 UK edition
Estimate your due date, current pregnancy week, conception window & BMI weight gain – based on NHS guidelines and NICE recommendations for 2026. Trusted by thousands of UK parents-to-be.
Pregnancy due date & week calculator (NHS method)
Use the NHS‑recommended Naegele’s rule: 280 days (40 weeks) from the first day of your Last Menstrual Period (LMP). You can also calculate from your estimated due date. For 2026, updated for cycle length adjustments.
NHS Pregnancy weight gain & BMI guidelines 2026
Your pre-pregnancy BMI influences healthy weight gain. Use the table below for UK recommendations:
| BMI category | BMI range (kg/m²) | Recommended total weight gain (kg) | NHS advice |
|---|---|---|---|
| Underweight | < 18.5 | 12.5 – 18 kg | Regular growth scans, balanced diet |
| Normal weight | 18.5 – 24.9 | 11.5 – 16 kg | Steady gain, active lifestyle |
| Overweight | 25 – 29.9 | 7 – 11.5 kg | Focus on nutrient-dense foods |
| Obese | ≥ 30 | 5 – 9 kg | Consult midwife, specialist support |
💡 Exclusive 2026 insight: New NICE quality statement encourages early BMI assessment at booking appointment. Use our BMI pregnancy calculator to check your category.
Pregnancy week by week – NHS timeline
| Trimester | Weeks | Key milestones / NHS care |
|---|---|---|
| First | Weeks 1–12 | Booking appointment, dating scan (8–14w), morning sickness peak, nuchal translucency scan |
| Second | Weeks 13–27 | Anomaly scan (18–20w), feeling baby movements, midwife check-ups, glucose screening if risk |
| Third | Weeks 28–40+ | Growth scans, birthing plan, antenatal classes, cervical screening, post-term assessment |
Exclusive: How to calculate pregnancy weeks accurately (NHS & 2026 updates)
- LMP method: For regular cycles (21–35 days), add 280 days to LMP to get due date.
- Cycle length correction: If cycle >28 days, add (cycle_length - 28) days to EDD. Our calculator automatically applies NHS adjustment.
- Early ultrasound (dating scan): The most reliable method – crown-rump length measurement between 10–14 weeks.
- Conception date: Ovulation usually occurs around day 14, but for IVF or tracked ovulation, add 266 days from conception.
🔍 Quick tip for 2026: NHS digital tools now integrate with maternity notes; this calculator mirrors the same gestational algorithm used by midwives.
Frequently asked questions – NHS pregnancy tools
It provides an estimate based on LMP or EDD. Dating scan (NHS) remains the gold standard for adjusting due dates. Accuracy is high for regular cycles.
Yes, but we recommend entering your average cycle length and confirming with an early ultrasound. Our tool includes cycle adjustment for more personalised results.
Depends on pre-pregnancy BMI (see table above). For normal BMI, 11.5–16 kg is advised. Speak to your midwife for individual support.
Count the number of days since LMP and divide by 7. The NHS uses completed weeks. Our calculator shows weeks + days and due date automatically.
For accuracy, wait 14 days after ovulation or missed period. NHS recommends testing from the first day of a missed period. Our ovulation/conception insights help.
IVF due date is calculated from embryo transfer date minus 2–5 days (depending on embryo age). For IVF, we suggest using the NHS dating scan. You can approximate with conception date.
No, but it follows NICE and NHS digital guidelines. Always confirm with your midwife. TotalCalcHub provides estimation tools, not medical advice.
Important medical disclaimer – UK edition
TotalCalcHub NHS pregnancy calculator is for informational purposes only. Not a substitute for professional midwifery or obstetric care. Always attend NHS antenatal appointments and rely on your dating scan for exact gestation. Results may vary due to individual health factors. Updated for 2026 guidelines.