What each tool does
Age Calculator
To calculate exact age, subtract the birth date from today's date in full years, then full months, then remaining days. If the birth day of the month hasn't been reached yet, borrow the number of days in the previous month. Someone born on 15 June 1995 is 31 years, 4 months and 19 days old on 3 November 2026.
Percentage Calculator
X% of Y equals X ÷ 100 × Y, so 15% of 240 is 36. To find what percent A is of B, divide A by B and multiply by 100. Percentage change is (new − old) ÷ old × 100, so going from 80 to 100 is a 25% increase.
Days Between Dates
To count days between two dates, subtract the earlier date from the later one. The result excludes the end date; add one day if both the first and last day should count. Working days exclude Saturdays and Sundays but not public holidays, which differ by country.
GPA Calculator
GPA is the average of your grade points weighted by credit hours: multiply each course's grade points (A = 4.0, B = 3.0, and so on) by its credits, add them up, and divide by total credits. To convert a CBSE CGPA to a percentage, multiply by 9.5.
Grade Calculator
A weighted grade is the sum of each score multiplied by its weight, divided by the total weight. For example, 85% on homework worth 30% and 72% on a midterm worth 30% gives (85×30 + 72×30) ÷ 60 = 78.5%. To find the final exam score you need: (target − current grade × (1 − final weight)) ÷ final weight.
Hours Calculator
To calculate hours worked, subtract the start time from the end time and take off any unpaid break. 9:00 am to 5:30 pm is 8 hours 30 minutes; minus a 30-minute lunch gives 8 hours. Shifts that cross midnight add 24 hours to the end time. In decimal hours, 8 h 15 m is 8.25 hours.
Proportion Calculator
To solve a proportion a/b = c/x, cross multiply: a × x = b × c, so x = (b × c) ÷ a. For example, 3/4 = 9/x gives x = (4 × 9) ÷ 3 = 12. The same method scales recipes, maps and prices: if 3 apples cost $4, 9 apples cost $12.
Area Calculator
Area of a rectangle = length × width; triangle = ½ × base × height; circle = π × radius²; trapezoid = ½ × (a + b) × height. A room 12 ft by 15 ft is 180 sq ft, which is 16.72 m². One square metre is 10.764 square feet.