To naturalize, a lawful permanent resident must satisfy two separate residence tests measured over a statutory period: physical presence (a day-count) and continuous residence (an unbroken-residence requirement). They sound similar but are counted differently, and applicants who pass one can still fail the other. This calculator counts both from your list of trips abroad and flags the absences that put continuous residence at risk.
The 30-month and 18-month physical-presence rules
On the general 5-year basis you must have been physically present in the United States for at least 30 months — 913 days — of the 5 years immediately before filing Form N-400. If you qualify under the 3-year basis (you have been a permanent resident for 3 years, are married to and living with the same U.S. citizen for those 3 years, and your spouse has been a citizen the whole time), the requirement drops to 18 months — 548 days of the 3-year period.
Day-counting follows a specific USCIS convention: the day you leave the United States and the day you return both count as days you were present. So a trip's days abroad equal the calendar gap minus one. This calculator applies that rule and clips any trip to the statutory window so partial trips at the edges count correctly.
Continuous residence and the 6-month and 1-year trip rules
Continuous residence is about whether you kept the U.S. as your home without a disrupting break, not about counting days. A single absence of more than 6 months but less than 1 year (roughly 180–364 days) creates a rebuttable presumption that you broke continuous residence — you can overcome it with evidence that you kept a job, home, family, and tax residence in the U.S. A single absence of 1 year or more (365+ days) generally breaks continuous residence outright unless you obtained an approved Application to Preserve Residence (Form N-470), and it usually resets the clock on eligibility. Because you can clear the 913-day presence test and still have a continuity problem, this calculator flags long trips separately from the day-count.
The 90-day early-filing window and what this tool does not do
You may file your N-400 up to 90 days before you complete the required 5 or 3 years of continuous residence. The calculator shows that earliest filing date based on your statutory-period anniversary. Keep in mind this tool is an educational planning aid: it does not account for the 3-month state/district residence requirement, exceptions for military service or certain overseas employment, reentry permits, time as a conditional resident, or the discretion USCIS exercises on the facts of your case. Use it to understand where you stand, then confirm with the USCIS Policy Manual or a licensed immigration attorney before relying on any number.