Your All-in-One Calculator Solution

About BMI

Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women.

BMI Categories:

• Underweight: BMI less than 18.5
• Normal weight: BMI 18.5–24.9
• Overweight: BMI 25–29.9
• Obesity: BMI 30 or greater

About Loan Calculations

This calculator uses the standard formula for fixed-rate loans to determine your monthly payment:

M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]

Where:

• M = Monthly payment
• P = Loan amount
• i = Monthly interest rate (annual rate divided by 12)
• n = Number of payments (loan term in years multiplied by 12)

About Investment Growth

This calculator uses compound interest formula to project the growth of your investments:

FV = PV (1 + r)^n + PMT [((1 + r)^n - 1) / r]

Where:

• FV = Future Value
• PV = Present Value (initial investment)
• PMT = Periodic payment (monthly contribution)
• r = Periodic interest rate (annual rate divided by 12)
• n = Number of periods (years multiplied by 12)

About Unit Conversion

This calculator converts between different units of measurement for length, weight, volume, and temperature.

All conversions are based on standard conversion factors:

• 1 inch = 2.54 centimeters
• 1 pound = 0.453592 kilograms
• 1 gallon (US) = 3.78541 liters
• °F = (°C × 9/5) + 32
• K = °C + 273.15

About Age Calculation

This calculator determines your exact age in years, months, and days based on your date of birth.

If no "Age at This Date" is provided, it will calculate your current age.

The calculation accounts for leap years and varying month lengths to provide an accurate result.

About Mortgage Calculations

This calculator helps you estimate your monthly mortgage payment including principal, interest, taxes, and insurance (PITI).

The principal and interest payment is calculated using the same formula as the loan calculator, while taxes and insurance are added as monthly amounts.

About Calorie Calculations

This calculator estimates your daily calorie needs based on the Mifflin-St Jeor Equation, which is considered one of the most accurate formulas.

The formula differs for men and women:

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) + 5

Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) - 161

Your BMR is then multiplied by your activity factor to estimate your maintenance calories.

About Currency Conversion

This calculator converts between major world currencies using current exchange rates.

For demonstration purposes, we're using fixed exchange rates. In a real application, you would fetch live rates from a currency API.

Common currency conversion APIs include:

• ExchangeRate-API
• Open Exchange Rates
• CurrencyLayer
• Fixer.io

About Date Calculations

This calculator determines the exact number of days between two dates.

The calculation accounts for leap years and correctly handles month lengths.

You can use this to calculate:

• Days until an event
• Days since an event
• Duration between two dates

About Body Fat Percentage

This calculator estimates body fat percentage using the U.S. Navy method, which requires only a few measurements.

The formulas differ for men and women:

Men: %Fat = 495 / (1.0324 - 0.19077 * log10(waist - neck) + 0.15456 * log10(height)) - 450

Women: %Fat = 495 / (1.29579 - 0.35004 * log10(waist + hip - neck) + 0.22100 * log10(height)) - 450

Note: For this simplified version, we're using fixed height values. A complete version would include height input.

About Pregnancy Calculations

This calculator estimates your due date based on the first day of your last menstrual period (LMP).

The most common method is Naegele's rule:

Due Date = LMP + 1 year - 3 months + 7 days

This assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, the calculation adjusts accordingly.

Note: Only about 5% of women deliver on their exact due date. Most deliver within 2 weeks before or after.

About Time Calculations

This calculator adds or subtracts time durations in hours, minutes, and seconds.

Time should be entered in HH:MM:SS format (24-hour clock). Examples:

• 08:30:00 (8 hours, 30 minutes)
• 13:45:15 (1:45:15 PM)
• 24:00:00 (24 hours)

The calculator handles overflow between units (e.g., 60 minutes becomes 1 hour).

About Retirement Planning

This calculator projects your retirement savings and estimates whether your savings can support your desired retirement income.

Assumptions:

• Retirement lasts until age 95
• During retirement, savings grow at 4% annually
• Inflation is not accounted for in this simplified version

A more complete version would include:

• Social Security/pension income
• Inflation adjustments
• Tax considerations
• Variable spending in retirement

About the Scientific Calculator

This calculator supports basic and advanced mathematical operations including:

• Basic arithmetic (+, -, ×, ÷)
• Exponents and roots (^, √)
• Trigonometric functions (sin, cos, tan)
• Logarithms (log, ln)
• Constants (π, e)
• Parentheses for order of operations

Note: This is a simplified version. A complete implementation would use a math parser library for more robust evaluation.

About Geometry Calculations

This calculator computes area and perimeter/circumference for common geometric shapes.

Formulas used:

• Square: Area = side², Perimeter = 4 × side
• Rectangle: Area = length × width, Perimeter = 2 × (length + width)
• Circle: Area = π × radius², Circumference = 2 × π × radius
• Triangle: Area = ½ × base × height, Perimeter = sum of all sides

About Percentage Calculations

This calculator helps with common percentage calculations:

• What is X% of Y? Calculates the percentage of a number.
• X is what % of Y? Finds what percentage one number is of another.
• X increased/decreased by Y%: Calculates the result of increasing or decreasing a number by a percentage.

Formulas used:

• X% of Y = (X / 100) × Y
• X is what % of Y = (X / Y) × 100
• X increased by Y% = X × (1 + Y/100)
• X decreased by Y% = X × (1 - Y/100)