Months to Days Calculator

Converting months to days is a common need in loan amortization, lease agreements, project planning, medical dosing schedules, and anywhere a duration specified in months needs to be expressed as a day count. Because individual calendar months vary in length — ranging from 28 to 31 days — an average is required for general-purpose conversion. This calculator uses 30.4375 days per month, the astronomically correct average derived from the Gregorian calendar's 365.25-day year divided by 12 months. This is more precise than the common rough approximation of 30 days, which introduces a 1.46% error per year that compounds meaningfully over multi-year timelines. For example, using 30 days per month over 12 months gives 360 days instead of 365.25, a difference of over five days. Whether you are planning a 3-month project sprint, checking how many days are in a 6-month trial period, or estimating a loan's day count for interest accrual, this calculator provides a precise and defensible result.

Calendar months are not equal in length — they range from 28 to 31 days depending on the month and whether the year is a leap year. To produce a consistent and accurate conversion, this calculator multiplies the number of months by 30.4375, which is the mean number of days per month derived from dividing 365.25 days per year by 12. The 365.25 figure accounts for the leap year cycle: three years of 365 days followed by one year of 366 days averages to 365.25 days per year. This method is the standard used in financial, scientific, and legal contexts when an exact calendar is not specified. For example, 6 months × 30.4375 = 182.625 days, and 12 months × 30.4375 = 365.25 days.