# Menstrual Cycle Calculator
 
## Tool Introduction
 
Online menstrual cycle calculator for women's safe period and ovulation period. Based on user input of menstrual cycle information, it quickly calculates safe periods, ovulation periods, and menstrual periods, helping women manage their health reasonably and providing scientific reference for pregnancy planning or contraception.
 
This tool supports customizable cycle parameters, and calculation results are presented in calendar format for easy viewing and planning. The calendar view updates in real-time when configuration parameters are modified.
 
## Features
 
- **Smart Calculation**: Based on scientific menstrual cycle calculation principles
- **Visual Calendar**: Intuitive calendar display with different colors for different periods
- **Customizable Parameters**: Support for personalized cycle length and menstrual duration settings
- **Multi-month Display**: Option to display 1-6 months of predicted results
- **Real-time Updates**: Immediate update of calculation results after parameter modification
- **Mobile Friendly**: Responsive design supporting phones and tablets
 
## Calculation Principles
 
### Basic Concepts
 
- **Menstrual Period**: Generally lasts 5-7 days, the time of menstrual bleeding
- **Ovulation Day**: Usually 14 days before the next menstrual period
- **Ovulation Period**: 5 days before and 4 days after ovulation day, totaling 10 days with higher conception probability
- **Safe Period**: Time outside the ovulation period with lower conception probability, but not absolutely safe
 
### Calculation Method
 
Normal menstrual cycles are generally 25-35 days. After menstruation begins, it usually lasts 5-7 days as the menstrual period. The ovulation day is 14 days before the next menstruation. The 5 days before and 4 days after ovulation day, together with the ovulation day, constitute a 10-day ovulation period. The remaining dates are safe periods.
 
In the calendar, the dark color represents the ovulation day, which is 14 days before the next menstruation. The 5 days before and 4 days after are also considered ovulation period, during which the possibility of conception is relatively high.
 
## How to Use
 
### Step 1: Enter the Last Menstrual Period Start Date
Select the date when your last menstrual period started, which is the basic data for calculation.
 
### Step 2: Set Average Menstrual Cycle Days
Enter your average menstrual cycle length, usually 25-35 days, default is 28 days.
 
### Step 3: Set Menstrual Duration Days
Enter how many days your menstruation usually lasts, generally 3-10 days, default is 5 days.
 
### Step 4: Select Display Months
Choose how many months you want to view, options are 1, 2, 3, or 6 months. The tool will automatically update the calculation results in real-time.
 
## Calendar Legend
 
- 🔴 **Red**: Menstrual period (menstruation)
- 🟠 **Orange**: Ovulation day (highest conception probability)
- 🟡 **Yellow**: Ovulation period (higher conception probability)
- 🟢 **Green**: Safe period (lower conception probability)
 
## Frequently Asked Questions (FAQ)
 
### Is the calculation result of this tool accurate?
The calculation is based on common menstrual cycle patterns, but individual differences are significant, so it's for reference only. For precise measurement, it's recommended to combine with basal body temperature or ovulation test strips.
 
### How does the ovulation period affect conception?
The ovulation period is the time with the highest conception probability. Women who want to conceive or avoid pregnancy can refer to this timing for life planning.
 
### Does the calculator support irregular menstrual cycles?
It supports customizable menstrual cycle days, but if the cycle is irregular, it's recommended to combine with other monitoring methods such as basal body temperature measurement and ovulation test strips.
 
### Is it suitable for all women?
It's suitable for most women with regular menstruation. If there are menstrual abnormalities or reproductive health issues, it's recommended to consult a professional doctor.
 
### Is safe period contraception reliable?
The effectiveness of safe period contraception is relatively low because ovulation timing may change due to various factors. For reliable contraception, other contraceptive methods are recommended.
 
## Important Reminders
 
⚠️ **Precautions**:
- Due to various influencing factors, menstrual cycles may not be stable, calculation results are for reference only
- This tool cannot replace professional medical advice
- If you have irregular menstruation or other gynecological problems, please seek medical attention promptly
- Safe period contraception is not 100% reliable, please choose more reliable methods if contraception is needed
- During pregnancy planning, it's recommended to combine with other monitoring methods to improve accuracy
 
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