Days to Months Calculator

Months are the most human-scaled time unit for medium-length durations — lease terms, loan tenors, subscription lengths, and project phases are almost always expressed in months. But many date calculations return results in days, making it necessary to convert. Because calendar months vary in length (28 to 31 days), a precise conversion requires an average. This calculator uses 30.4375 days per month — derived from the astronomically accurate year of 365.25 days divided by 12 months — to produce a consistent and repeatable result. The output is ideal for financial modelling, age estimations, and anywhere you need months expressed as a decimal rather than calendar counting.

Months = Days ÷ 30.4375. The divisor 30.4375 is calculated as 365.25 ÷ 12, where 365.25 is the mean tropical year length accounting for the leap year cycle. This makes the conversion astronomically consistent rather than arbitrarily rounding to 30 or 31. For example, 90 days ÷ 30.4375 = 2.9569 months; 365 days ÷ 30.4375 = 11.9918 months (close to but not exactly 12 because a calendar year of 365 days is 0.25 days shorter than the average year). Results are displayed to four decimal places.