Ovulation Calculator
Estimates ovulation and the fertile window.
Result
- Estimated ovulation day
- 15 Mar 2026
- Fertile window starts
- 10 Mar 2026
- Next period expected
- 29 Mar 2026
How to use the ovulation calculator
- Enter the first day of last period.
- Enter the cycle length (days).
- The results update as you type, or press Calculate.
- Read the estimated ovulation day first, then the supporting figures below it.
Formula
Ovulation ≈ cycle length − 14 days after the period starts.
Worked example
For example, with these inputs:
- First day of last period: 1 Mar 2026
- Cycle length (days): 28
the calculator returns:
- Estimated ovulation day: 15 Mar 2026
- Fertile window starts: 10 Mar 2026
- Next period expected: 29 Mar 2026
Background
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.
Research has shown that Asians tend to develop conditions such as type 2 diabetes and heart disease at lower body weights than Europeans. That is why the Health Promotion Board recommends lower BMI cut-offs for Singaporeans, with 23 marking the start of moderate risk.
Frequently asked questions
How does the ovulation calculator work?
It applies this formula: Ovulation ≈ cycle length − 14 days after the period starts.
Is this a medical assessment?
No. These are general estimates. Speak to a doctor or polyclinic for advice about your health.