How these everyday calculators work
Age calculator computes your exact age by comparing your date of birth to today. It accounts for leap years and different month lengths, returning your age in years, months, and days as well as the total number of days you have been alive.
Date difference calculator finds the number of days, weeks, months, and years between any two dates. This is useful for project planning, calculating contract durations, and determining deadlines.
Days until calculator tells you how many days remain until any future date or how many days have passed since a past date. Use it for countdowns to birthdays, holidays, travel dates, or deadlines.
Sleep calculator is based on sleep cycle science. The average sleep cycle lasts 90 minutes, and waking up at the end of a cycle rather than in the middle leaves you feeling more rested. The calculator shows six possible wake times or bedtimes based on 90-minute intervals starting from your input time.
GPA calculator converts numerical grades to the 4.0 GPA scale and weights each course by credit hours. An A (90 to 100) earns 4.0 points, a B (80 to 89) earns 3.0, a C (70 to 79) earns 2.0, a D (60 to 69) earns 1.0, and below 60 earns 0.0. Add as many courses as needed.
Frequently asked questions
- Why do I feel groggy when I wake up from an alarm?
- Grogginess on waking is called sleep inertia and is most severe when you are woken in the middle of a deep sleep stage. Timing your wake-up to the end of a 90-minute sleep cycle reduces the chance of this happening. The sleep calculator helps you choose a bedtime so your alarm catches you at the right point.
- How do I calculate GPA for graduate school applications?
- Enter each course grade and its credit hours, then click Calculate GPA. Most graduate programs look at your overall GPA and your GPA in courses relevant to your field. If you have more than the default rows, click Add Course to add as many rows as you need.
- Does the date calculator handle leap years?
- Yes. The calculation uses the actual number of days in each month and year, including February 29 in leap years, so results are always accurate regardless of the dates you enter.