If you searched for a calculador regla, you probably want one thing: a fast, reliable way to estimate your next period date and better understand your cycle. This calculator helps you do exactly that in seconds.
Calculador Regla (Period Calculator)
Enter your cycle details to estimate your next period, likely ovulation day, and fertile window.
Note: This tool is for estimation only and is not a medical diagnosis.
What is a calculador regla?
A calculador regla is a menstrual cycle calculator. It estimates important dates based on the first day of your last period and your average cycle length. Most people use it to:
- Predict the start date of their next period
- Plan for travel, events, or athletic activity
- Identify likely ovulation and fertile days
- Track cycle changes over time
How this calculator works
The logic is straightforward:
- Next period date = recent cycle start + cycle length
- Estimated period end = next period start + period length - 1 day
- Estimated ovulation = about 14 days before the next period
- Estimated fertile window = roughly 5 days before ovulation through 1 day after
These values are averages. Real cycles can vary from month to month because of stress, sleep, travel, illness, exercise changes, medications, and hormonal conditions.
Step-by-step: getting the best estimate
1) Use accurate cycle history
If possible, base your cycle length on the average of your last 3 to 6 cycles, not just one month.
2) Enter the first day of bleeding
Day 1 is the first day of full menstrual flow, not spotting.
3) Recalculate monthly
Update your data after each cycle. This keeps your forecast realistic and useful.
Understanding your results
After you calculate, you will see:
- Next period start: your estimated upcoming day 1
- Estimated period end: when bleeding may finish
- Estimated ovulation day: likely release of an egg
- Fertile window: days with highest chance of conception
- Cycle forecast: predictions for the next several cycles
When predictions may be less accurate
Any calculator is less precise when cycles are irregular. Consider adding a few days of margin if any of these apply:
- Cycles shorter than 21 days or longer than 35 days
- Recent pregnancy, breastfeeding, or stopping hormonal birth control
- Perimenopause or endocrine conditions (e.g., thyroid issues, PCOS)
- Major lifestyle changes (night shifts, intense training, jet lag)
Healthy tracking habits
Track symptoms too
Record cramps, mood changes, sleep, cervical mucus, and basal body temperature if you want deeper insight into your cycle patterns.
Keep records private and simple
This page calculates in your browser and does not require account creation. You can copy results into your preferred journal or calendar.
Frequently asked questions
Is this calculator a pregnancy test?
No. If your period is late and pregnancy is possible, use a pregnancy test and follow up with a healthcare professional.
Can I use this as birth control?
Cycle prediction alone should not be considered a reliable contraceptive method. Talk with your clinician about evidence-based options.
What if my cycle changes often?
Use longer-term averages, keep symptom notes, and speak with a professional if irregularity is frequent or concerning.
Final thoughts
A good calculador regla gives you practical guidance for planning and self-awareness. Use it as a helpful forecast, not a guarantee, and combine it with monthly tracking for better accuracy over time.