Fifteen days is two weeks and one day, so the end date lands one weekday past today. Fifteen days from a Monday is a Tuesday, and from a Friday it is a Saturday.
Most 15-day deadlines exist because someone wanted half a month without having to specify which month. That approximation is close but never exact, and the difference is what makes 15-day windows worth checking rather than estimating.
Net 15 and other 15-day windows
Fifteen days is the shortest payment term in routine commercial use:
- Invoicing: net 15 means payment is due 15 calendar days from the invoice date, and it is the standard term for freelancers and small suppliers who cannot carry a 30-day float
- Trials: 15-day free trials sit between the 7-day trial that is too short to form a habit and the 30-day trial that costs the vendor a month of hosting
- Grace periods: insurance premium grace periods commonly run 10 to 31 days depending on the policy type and state, with 15 a frequent middle setting
- Contracts: 15-day cure notices, requiring a breach to be remedied before termination, are common in service agreements
- Returns: 15-day return windows are typical for opened electronics and made-to-order goods
Because 15 days is not a whole number of weeks, a 15-day term set on a Friday falls due on a Saturday, and in practice moves to the following Monday. If the exact day matters, confirm whether the agreement rolls forward to the next business day or stays on the calendar date.
15 days is not quite half a month
Half a calendar month is 14 days in February, 15 in a 30-day month, and 15.5 in a 31-day month. So 15 days is exactly half a month only in April, June, September and November.
The gap shows up most clearly in payroll. Semi-monthly pay, usually the 15th and the last day of the month, produces 24 pay periods averaging 15.2 days each. Biweekly pay produces 26 periods of exactly 14 days. Those two are frequently treated as interchangeable and are not: biweekly gives employees two extra paychecks a year and shifts weekday, while semi-monthly holds the calendar date and varies the interval.
The 15th of the month also carries the heaviest date load in the US tax calendar, with estimated payments due 15 April, 15 June, 15 September and 15 January. Those are day-of-month deadlines, not 15-day counts, but they are why "the 15th" reads as a deadline to most people.
Business days in 15 days
Fifteen calendar days contain 10 or 11 weekdays: 11 from a Sunday, Monday, Tuesday, Wednesday or Thursday start, and 10 from a Friday or Saturday start, assuming a Monday-to-Friday week.
Across a 15-day window you can expect a public holiday less than half the time, so 10 or 11 is usually the real working figure rather than an upper bound.
If a document specifies 15 business days instead, that is 19 to 21 calendar days, roughly three weeks. The two readings differ by nearly a week, which is more than enough to miss a cure period.
Frequently Asked Questions
How many weeks is 15 days?
Two weeks and one day. Because 15 is not a multiple of seven, the end date falls one weekday past your starting weekday, so 15 days from a Monday is a Tuesday.
Is 15 days half a month?
Only in April, June, September and November. Half a calendar month is 14 days in February, 15 in a 30-day month, and 15.5 in a 31-day month, so 15 days is an approximation everywhere else.
What does net 15 mean?
Payment is due 15 calendar days from the invoice date, weekends included. If day 15 falls on a weekend, most agreements expect payment on the next business day, but that depends on the wording rather than the count.
How many business days are in 15 calendar days?
10 or 11, before subtracting public holidays. It is 11 from a Sunday through Thursday start and 10 from a Friday or Saturday start. If a document says 15 business days instead, that is 19 to 21 calendar days.