Weeks Between Dates Calculator

The weeks between dates calculator finds the exact number of complete weeks — and any remaining days — between any two calendar dates. Enter your start and end dates using separate year, month, and day fields to get whole weeks, leftover days, total days, and an approximate month count. This is useful for pregnancy tracking (gestational weeks from LMP), training plan scheduling, project timelines, event countdowns, subscription billing periods, lease durations, and any situation where measuring time in weeks gives more useful precision than months or years. Unlike a month-based counter, a week count is unambiguous — weeks are always exactly 7 days, so 12 weeks always means 84 days. This makes the calculator especially reliable for medical and fitness contexts where precise duration matters and calendar month variation could cause confusion. The result also includes a total day count and an approximate month figure, giving you multiple ways to communicate the same elapsed time depending on whether your audience or application prefers days, weeks, or months.

The calculator converts both dates to JavaScript Date objects and subtracts them to get total milliseconds, which is divided by 86,400,000 (milliseconds per day) and rounded to get total days. Weeks are found by dividing total days by 7. The whole number of weeks is the floor of that result; the remainder (total days modulo 7) gives the leftover days beyond the last complete week. For example, 85 total days ÷ 7 = 12 whole weeks with 1 remaining day. Approximate months divide total days by 30.4375, the average calendar month length (365.25 ÷ 12), which accounts for leap years over time. Because this calculator uses raw day counts rather than calendar month arithmetic, it avoids the ambiguity caused by months of unequal length and produces consistent, reproducible results regardless of which months fall within the span.