Pregnancy Due Date: 5 Mistakes to Avoid
Estimates your due date using Naegele's rule. The maths is not complicated, but a handful of errors come up again and again in this and related health & fitness calculations. Here is what to watch for.
Singapore's tropical climate means you lose more fluid through sweat, even when you are not exercising. Thirst, urine colour and how you feel are good guides, and needs rise during outdoor activity or heat waves.
Programmes such as the National Steps Challenge and the Healthy 365 app have made tracking activity common. Turning those numbers into distance, pace or calories helps set realistic goals for events like IPPT or a 10 km run.
1. Using international BMI cut-offs for Asians
HPB recommends lower cut-offs because risks rise at lower BMIs in Asian populations.
2. Treating estimates as exact
Formulas such as BMR or body fat are population estimates with real margins of error.
3. Relying on a single measurement
Weight and heart rate fluctuate daily; trends tell you more.
4. Cutting calories too aggressively
Very large deficits are hard to sustain and can lead to muscle loss.
5. Measuring inconsistently
Tape measurements change with posture and breathing; measure the same way each time.
The correct method
Due date = first day of last period + 280 days.
For example, with these inputs:
- First day of last period: 1 Mar 2026
the calculator returns:
- Estimated due date: 6 Dec 2026
- End of first trimester: 6 Jun 2026
Related calculations
- Ideal Weight Calculator: Gives an ideal-weight estimate and the healthy weight range for your height.
- Daily Water Intake Calculator: A rough guide to daily fluid needs in Singapore's hot, humid climate.
- Calorie Deficit Calculator: Sets a daily calorie target for steady weight loss.
- Ovulation Calculator: Estimates ovulation and the fertile window.
The Pregnancy Due Date Calculator applies the formula consistently, so it is a quick way to double-check your own working.
Run your own numbers: Pregnancy Due Date Calculator