Counting to five years sounds like arithmetic until absences, gaps between permits, and time spent on a study permit enter the picture. Long-term residents planning an application need to know what interrupts the count, because a miscount usually only surfaces once the file is already in.
IND's standard is a valid Dutch residence permit for at least five consecutive years with the Netherlands as your main residence throughout — in practice the clock runs from your first valid permit's start date, though IND doesn't spell out an exact "day one" rule, so treat that as the best available reading rather than gospel. What breaks continuity is more concrete: under IND's main-residency test, a single absence longer than six continuous months within one calendar year, or more than four continuous months in each of three consecutive years, lets IND treat you as having moved abroad — those thresholds aren't summed across years, they're assessed within each one. A genuine gap between permits can also interrupt continuity, though renewing within four weeks of expiry isn't treated as a gap. Whether time on a study or temporary permit counts fully toward the five years is genuinely disputed among immigration lawyers — some say it counts the same as any other permit, others say it's discounted — so don't assume either way. You'll also need to pass the civic integration exam at A2 level (or hold an exemption) as a standalone requirement for this permit, separate from naturalisation. Given how fact-specific this gets, ask IND or a lawyer to check your actual file.