Pregnancy Due Date Calculator
Work out your estimated due date and how many weeks pregnant you are.
Your result
Updates as you type. Based on 2025/26 UK figures where relevant.
How this is worked out
The due date is 280 days (40 weeks) after the first day of your last period. Your dating scan may adjust this.
Tips
- The NHS uses BMI as a screening tool, but waist measurement also matters.
- Estimates like BMR and body fat can vary by 5–10% from lab measurements.
- Track trends over weeks rather than day-to-day changes.
Guides for this calculator
- How to Calculate Your Pregnancy Due Date in the UK: Step-by-Step Guide
- Your Pregnancy Due Date: Common Mistakes, Tips and FAQs
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Frequently asked questions
How does the pregnancy Due Date Calculator work?
The due date is 280 days (40 weeks) after the first day of your last period. Your dating scan may adjust this.
Is this medical advice?
No. These tools give general estimates. For medical advice, speak to your GP, pharmacist or NHS 111.
Can I use these for children?
No. Children's BMI and health measures use age- and sex-specific charts. Use the NHS healthy weight calculator for children.
Why use stone and pounds?
Many people in the UK still think in stone and pounds, so we accept those units and show metric too.
This calculator gives an estimate for general information. It isn't financial, tax, legal or medical advice. Check official figures on GOV.UK or NHS.uk, or speak to a qualified adviser.