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Accurate time conversion tool for months and days
Convert months to days instantly with precise calculations. Includes bidirectional conversion, Gregorian average and leap year modes, and full time breakdowns across weeks, hours, minutes and seconds for 2026.
Professional time conversion for project planning, medicine, finance, and calendar calculations
Convert months to days using the Gregorian calendar average of 30.436875 days per month — derived from the exact 365.2425-day Gregorian year divided by 12. Our Months to Days Converter also supports a simplified 30-day month and leap year mode (30.5 days/month average), giving you the right precision for medical dosing schedules, project timelines, financial periods, and academic research requiring different calendar bases.
Switch instantly between months to days and days to months conversion modes. Results are also displayed across weeks, hours, minutes, and seconds — providing a complete time picture from a single input for project managers, healthcare professionals, financial analysts, and anyone needing to convert time intervals across multiple units in one step.
Essential for medical treatment duration tracking, project milestone planning, financial term calculations, pregnancy and gestational age conversion, loan and mortgage period analysis, and calendar-based scheduling. Whether you are converting a 6-month contract to days, calculating a pregnancy timeline, or determining days in a billing period, the Months to Days Converter gives fast and reliable results for 2026.
Select conversion direction, choose your month type, and enter your value below
The month is a calendar unit of time based on the cycle of the Moon, ranging from 28 to 31 days depending on which calendar month is being referenced. The day is the fundamental unit of calendar time equal to 24 hours, based on one rotation of the Earth. Converting between these two units requires choosing a representative "month length" because months are not all the same length — February has 28 days (29 in a leap year), while January, March, May, July, August, October, and December each have 31 days, and April, June, September, and November each have 30 days.
For most general-purpose conversions, the Gregorian calendar average of 30.436875 days per month is used — derived by dividing the exact Gregorian year length of 365.2425 days by 12 months. This accounts for leap years and gives the most accurate average over long time spans. The simplified 30-day month is a convenient approximation used in banking, finance, and some medical contexts. Our Months to Days Converter supports all three bases so you get the right result for every type of time calculation — whether precise planning or quick estimation.
Example: 6 months × 30.436875 = 182.62 days | 90 days ÷ 30.436875 = 2.957 months
Each calendar month has a fixed number of days in standard years, with February gaining one extra day in leap years. This grid shows the exact day count for every month — essential context for precise month-to-day conversions when you know which specific months are involved rather than using an average.
Use this reference table for quick Months to Days lookups using the Gregorian calendar average (30.436875 days/month). Values cover 1 month through to 36 months (3 years) — spanning the most common time durations needed for project planning, medical treatment periods, financial terms, and personal milestone tracking.
| Months | Days (Gregorian) | Days (30-day avg) | Weeks | Reference |
|---|---|---|---|---|
| 1 month | 30.44 days | 30 days | 4.348 weeks | One calendar month |
| 2 months | 60.87 days | 60 days | 8.696 weeks | Two months |
| 3 months | 91.31 days | 90 days | 13.044 weeks | One quarter |
| 4 months | 121.75 days | 120 days | 17.393 weeks | Third of a year |
| 5 months | 152.18 days | 150 days | 21.741 weeks | Five months |
| 6 months | 182.62 days | 180 days | 26.089 weeks | Half year |
| 7 months | 213.06 days | 210 days | 30.437 weeks | Seven months |
| 8 months | 243.50 days | 240 days | 34.786 weeks | Eight months |
| 9 months | 273.93 days | 270 days | 39.134 weeks | Pregnancy term |
| 10 months | 304.37 days | 300 days | 43.482 weeks | Ten months |
| 11 months | 334.81 days | 330 days | 47.830 weeks | Eleven months |
| 12 months | 365.24 days | 360 days | 52.179 weeks | One full year |
| 18 months | 547.86 days | 540 days | 78.266 weeks | Year and a half |
| 24 months | 730.49 days | 720 days | 104.356 weeks | Two years |
| 36 months | 1,095.73 days | 1,080 days | 156.533 weeks | Three years |
The diagram below shows how months and days relate to other key time units — helping you put Months to Days Converter results into the broader context of the time measurement hierarchy from seconds to years.
One Gregorian year = 365.2425 days = 12 months = 52.1775 weeks — the average accounts for a leap year occurring every 4 years (with century-year exceptions)
The uneven length of calendar months stems from the Julian calendar reform by Julius Caesar in 46 BC, which alternated 30 and 31 day months to fit 365 days per year. February was assigned the remaining 28 days and designated as the intercalary month (getting an extra day in leap years). Augustus Caesar later adjusted the calendar to ensure August had 31 days equal to July, which created the run of three consecutive 31-day months (July, August, September) that breaks the original alternating pattern.
The Gregorian calendar averages 365.2425 days per year — accounting for leap years every 4 years (adding 1 day), minus century years (subtracting 1 day), plus 400-year cycles (adding 1 day back). Dividing 365.2425 by 12 months gives 30.436875 days per month — the most accurate average for calendar calculations spanning multiple years. This is the conversion factor used by scientific and engineering standards for months-to-days conversions.
In obstetrics, pregnancy is measured both in weeks and months. A full-term pregnancy is 40 weeks = approximately 280 days = 9.2 months. The "9 months of pregnancy" figure commonly cited in everyday language uses the simplified 30-day month (9 × 30 = 270 days), which slightly underestimates the actual 40-week (280-day) term. Medical professionals use gestational weeks for precision, while the Months to Days Converter bridges both counting systems for patient communications.
In banking and finance, a 30-day month (and 360-day year) is commonly used for interest calculations — known as the "30/360 day count convention." This simplifies interest accrual: every month is treated as exactly 30 days regardless of actual calendar days. A 6-month term deposit period = exactly 180 days under this convention. Our Months to Days Converter includes a 30-day mode specifically for financial period calculations alongside the more accurate Gregorian average.
Project management timelines often mix months and days — a 6-month project might be described in months for high-level planning but tracked in individual days at the task level. Using the Gregorian average of 30.44 days per month, a 6-month project = 182.6 days, a 3-month sprint = 91.3 days, and a 12-month roadmap = 365.2 days. The Months to Days Converter provides the precise day count alongside the full weekly and hourly breakdown needed for resource scheduling.
A leap year occurs when a year is divisible by 4 — except for century years (divisible by 100), which are only leap years if also divisible by 400. In 2026 (not a leap year), February has 28 days and the year has 365 days. In a leap year, the average month is slightly longer: 366 ÷ 12 = 30.5 days per month. Our converter's "leap year" mode uses this 30.5 factor for calculations tied specifically to a leap year's longer calendar. The next leap year after 2026 is 2028.
For a fast mental estimate, multiply months by 30 to get approximate days — it's only about 1.5% less than the precise Gregorian average. Key references to memorise: 1 month ≈ 30 days, 3 months ≈ 91 days, 6 months ≈ 183 days, 12 months ≈ 365 days. For going the other way, divide days by 30 for a quick month estimate — 90 days ÷ 30 = 3 months, 180 days ÷ 30 = 6 months. For precise results in planning, finance, or medicine, always use our Months to Days Converter with the Gregorian average setting.
Our converter is designed for speed and precision on any device. Follow these four steps to get your result instantly:
This reverse reference table shows common day values converted to months using the Gregorian average — useful when you have a duration in days (from a contract, medical record, or project log) and need to express it in months for reporting, billing, or planning purposes.
| Days | Months (Gregorian) | Months (30-day) | Weeks | Reference |
|---|---|---|---|---|
| 7 days | 0.230 months | 0.233 months | 1 week | One week |
| 14 days | 0.460 months | 0.467 months | 2 weeks | Fortnight |
| 28 days | 0.920 months | 0.933 months | 4 weeks | February (standard) |
| 30 days | 0.986 months | 1.000 months | 4.286 weeks | 30-day month |
| 31 days | 1.018 months | 1.033 months | 4.429 weeks | 31-day month |
| 60 days | 1.971 months | 2.000 months | 8.571 weeks | ~2 months |
| 90 days | 2.957 months | 3.000 months | 12.857 weeks | ~1 quarter |
| 120 days | 3.942 months | 4.000 months | 17.143 weeks | ~4 months |
| 180 days | 5.914 months | 6.000 months | 25.714 weeks | ~6 months |
| 270 days | 8.871 months | 9.000 months | 38.571 weeks | ~9 months (pregnancy) |
| 365 days | 11.993 months | 12.167 months | 52.143 weeks | Standard year |
| 366 days | 12.026 months | 12.200 months | 52.286 weeks | Leap year |
The Months to Days Converter uses an average month length — either Gregorian (30.436875 days), simplified (30 days), or leap year (30.5 days). These averages are appropriate for general planning and estimation. However, if you need to count the exact number of days between two specific calendar dates (e.g., from 1 March to 1 September), you should use a date calculator that counts actual calendar days month by month. For example, March + April + May + June + July + August = 31 + 30 + 31 + 30 + 31 + 31 = 184 days exactly, compared to the 6-month Gregorian average of 182.62 days.
Healthcare is one of the most important real-world applications of the Months to Days Converter. Medical treatment durations — antibiotic courses, chemotherapy cycles, psychiatric medication trials, and rehabilitation programmes — are often described in months for patient communication but must be tracked precisely in days for clinical records and dosing compliance. A 3-month antibiotic prophylaxis course equals 91.3 days (Gregorian) or 90 days (30-day basis), and a 6-month follow-up period equals 182.6 or 180 days respectively. Selecting the correct basis matters in clinical contexts.
Gestational age — the age of a foetus or newborn — is the most widely known medical months-to-days application. A full-term pregnancy spans 40 weeks = 280 days = approximately 9.2 months from the last menstrual period. Premature birth thresholds are defined in weeks (viability begins around 24 weeks = 168 days), while neonatal development milestones are tracked in both weeks and months after birth. Paediatric growth charts, vaccine schedules, and developmental assessments all require accurate months-to-days conversion for correct age-based interpretation across the first years of life.
The International Bureau of Weights and Measures (BIPM) defines the second as the SI base unit of time. The day (86,400 seconds) and the Gregorian calendar year (365.2425 days) are accepted non-SI units used in conjunction with SI. The BIPM maintains global consistency in time measurement standards that underpin all months-to-days and calendar-to-SI conversions used in science, engineering, and international commerce.
Visit BIPM →The US National Institute of Standards and Technology (NIST) maintains official time standards and provides authoritative definitions of calendar time units used in US scientific, legal, and commercial contexts. NIST Special Publication 811 defines the day as exactly 86,400 SI seconds, and NIST time services maintain the US national standard for clock synchronisation and calendar date accuracy.
Visit NIST →Explore our full collection of free conversion tools including area converters (acres to square metres, square yards), volume converters (teaspoons to millilitres), weight converters (tonnes to stones), length converters (yards to chains), power converters (watts to kilowatts), and pressure converters (atmospheres to pascals) — all free, mobile-friendly, and accurate for 2026.
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