6 Month Calculator

How it works

The calculator uses standard calendar month arithmetic, the same convention as contracts, spreadsheets and calendar apps. It keeps the day of the month fixed and shifts the month number by the amount you enter, rolling the year over when it passes December. So the 23rd of one month always maps to the 23rd of the target month. The one exception is when that day does not exist: add six months to 31 August and you land in February, which has only 28 days, or 29 in a leap year, so the result clamps to the last day of February. The days between figure is the exact count of calendar days from the start date to the result, and the weeks figure is that count divided by seven, rounded to one decimal place. Because month lengths vary, six months works out to between 181 and 184 days depending on your start point, which is why a months-based deadline and a days-based deadline can differ by several days.

Worked example

Using today as the start date, the calculator begins at 2 August 2026. Adding 6 months keeps the day of the month the same and moves forward 6 calendar months, giving 2 February 2027, which falls on a Tuesday. Counting the individual days between the two dates gives 184 days, which is 26.3 weeks. Going backwards instead, 6 months before 2 August 2026 is 2 February 2026. If you need a different span, change the number of months: the same method applies whether you are adding 3 months for a quarterly review or 18 months for a long fixed term.

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