Weeks Calculator - Calculate weeks between dates

  1. Subtract weeks: Use this calculator to find a date in the past by subtracting weeks from a start date.
  2. Weeks between dates: Find the number of weeks between two dates.
  3. Add weeks: Use this to find a date in the future by adding weeks to a start date.

Using our week calculators

We built the week calculator to help quickly solve counting weeks forward, before, and between two timeframes. These are three separate calculations and here's how you'd use each:

  1. Choose the type of calculation you need: There are a thousand ways to calculate dates by weeks.
    • Subtract Weeks is used for finding a date before the date you choose. For example: 7 weeks before June 3. This calculation will return April 15.
    • Weeks Between Dates will give you a specific number of weeks (rounded to the nearest week) when choosing two dates. For example: Weeks between April 14 and June 3. This calculation will return 7 weeks (see how it rounds to the weeks?).
    • Add Weeks counts forward from a specific date you choose. For example: 7 Weeks from April 14 will give you June 2 (again, see how the dates are similar, but we round for dates between?).
  2. Input your date & timeline: We've made it so it won't fully calculate until you fill both dates. Please contact us if you find a bug.
  3. Evaluate your answer: Again, we round all the time between two dates rounds to the nearest week. Make sure it makes sense. Additionally, you can find other week calculators we build for finding weeks before today, weeks from today, weeks until a specific date, and weeks from a specific date. These will bring you directly to specific date calculators.

How to calculate the number of weeks between two dates

We can start a week calculation manually by marking the date, year, and day of week. The fastest way to do this would be to use a calculator or use a formula if you're using excel or gsheets; alas, you'll still follow similar steps.

  1. Mark the start and end dates: This sounds simple, but always write it down because it will really help step two.
  2. Identify days of the week: Okay, this is far more important than you might think. If your two dates fall on the same day, you'll have a whole number as your weeks between. However, if your dates don't align, you'll have a remainder in days which sends us to step three.
  3. Convert to days: I do think for every calculation. I know it's tedious, but this gives us a total number of days we can then divide and calculate.
  4. Divide by 7: This coverts our number of days into weeks again. Remember we talked about days of the week? Now look at the day of the week for your first date and count by the remainder of days you have.
  5. Round (if you choose) to get your solution in weeks: Rounding is great for large numbers. Round to the nearest week if you're calculating weeks that span over months or years. If it's a coversion within a month or you need to be a bit more specific, consider using a remainder or even a day calculation could be a better choice.

Tips when calculating week values

  1. If your two dates are not the same day of the week, you'll get a remainder of days.
  2. Week calculations include the weekend. You'll need a new formula for workweek calculations.
  3. Round your final solution for larger week calculations and consider day calculations for shorter ones.

How to subtract weeks from a date

Subtracting weeks from a date can get tricky. Anytime we subtract time from a date, we have to be aware of the length of each month, where we're at in the year, whether it's a leap year, and even how many weeks would take us back multiple years. Counting backwards might seem simple, but we do need to pay attention to the details of recounting a past date. Other than using a calculator or formula, here's how I teach subtracting weeks:

  1. Convert to days: First thing I do is bring the calculation to a smaller unit. This will set us up nicely for steps two and three, but it gives us a look at the full calculation.
  2. Subtract: Subtract the days from your new number (in days). Yes, I know we started in weeks, and converted into days, but now we can get into the little details of step three.
  3. Identify blockers: Maybe I shouldn't call them blockers, but these are all the little details I mentioned above that can throw off our equation. Length of the month, years, leap years, etc. Once we've converted the days and subtracted, now account for all the days we'll need to remove from our final calculation.
  4. Identify the date: Once we converted weeks to days, subtracted days, and accounted for calendar changes, now we can clearly find our new date.

Tips when subtracting weeks

  • Know the number of days for the previous months.
  • Account for calendar changes like leap years.
  • Convert to days to calculate little details we might miss in weeks.

How to add weeks to a date

When we add weeks to a date, we're taking a similar process as subtracting, except we need to account for future calendar changes rather than recalling them. Let me explain:

  1. Convert to days: Similar to subtracting, we need to see the entire equation. Converting to days allows us to account for calendar changes and makes addition a bit easier. Do this by multiplying your number by 7.
  2. Identify challenges: You'll need to know how many days are in the month, future month's lengths, plus leap years, holidays, or any type of annual changes. This becomes even more important on larger calculations that span over months or years.
  3. Add your days: Once you have the changes in the calendar, we can do our addition and count forward to the desired date.

Tips when adding weeks