How the N-400 eligibility rules work
This calculator applies two USCIS requirements — continuous residence and physical presence — plus a 90-day early filing window. Every number below comes from the USCIS Policy Manual or the Code of Federal Regulations, linked at each step.
How does USCIS count days you spend outside the United States?
USCIS counts the day you leave and the day you return as days present in the United States, not as days absent. Only the days in between count against you.
"USCIS will count the day that an applicant departs from the United States and the day he or she returns as days of physical presence within the United States for naturalization purposes."
So for a trip that departs on d and returns on r, the days absent are (r − d) − 1, not the raw calendar difference. USCIS's own worked example proves it: an applicant who departs on January 1, 2010 and returns on January 2, 2011 has been outside the United States for exactly 365 days, even though the raw gap between those two dates is 366 days. A calculator that just subtracts dates overcounts every trip by two days — enough, across a travel history with many trips, to move your filing date.
Read the day-counting rule on uscis.gov (Policy Manual, Vol. 12, Part D, Chapter 4)
How many days must you be physically present before filing?
Under the general naturalization path (INA 316(a)), USCIS requires at least 913 days of physical presence in the United States before you file.
"Applicants for naturalization under INA 316(a) are required to demonstrate physical presence in the United States for at least 30 months (at least 913 days) before filing the application."
913 is not a round number and USCIS did not round it for you — it is exactly 30 months stated in days, and the calculator on this site counts toward that exact figure.
If you are applying as the spouse of a US citizen (INA 319(a)), the requirement is 3 years of continuous residence and 18 months of physical presence, plus 3 years married to and living in marital union with your spouse before filing. USCIS states this requirement in months, not days. Our calculator shows 548 days for this path, and we label it clearly as our own arithmetic (1,095 days ÷ 2, rounded up) — not a number USCIS has published.
Read the physical presence rule on uscis.gov (Policy Manual, Vol. 12, Part D, Chapter 4)
What counts as a break in continuous residence?
A single trip abroad can break continuous residence on its own, independent of your physical presence total. USCIS sets three thresholds for a single trip:
| Length of a single trip | What happens |
|---|---|
| 180 days or less | No presumption of a break. Continuous residence stands. |
| More than 180 days, less than 365 days | A rebuttable presumption that continuous residence broke. You can overcome it with evidence — kept US employment, immediate family who stayed in the US, or a US home you kept or leased. |
| 365 days or more | An automatic break. There is no evidence that rebuts this one, unless you hold an approved N-470. |
This calculator flags each trip against these three thresholds. A trip over 180 days shows as a caution, not a pass, even if your total physical presence days still add up — the two requirements are separate and a single long trip can fail continuous residence while physical presence still looks fine on paper.
Read the continuous residence rule on uscis.gov (Policy Manual, Vol. 12, Part D, Chapter 3) — see also our page on continuous residence.
Can you file Form N-400 before your anniversary date?
Yes. Federal regulation lets you file up to 90 days before you complete your required period of continuous residence.
"An application for naturalization may be filed up to 90 days prior to the completion of the required period of residence."
USCIS counts the 90 days back from the day before your continuous residence anniversary. In USCIS's own example, an applicant whose 5-year continuous residence period is first satisfied on June 10, 2010 can file as early as March 12, 2010 — 90 calendar days before that anniversary.
8 CFR 334.2(b) on Cornell Law and USCIS Policy Manual, Vol. 12, Part D, Chapter 6
Is filing early the same as being eligible early?
No. Filing early and being eligible are two different dates, and USCIS says so directly.
"Although an alien may file early according to the 90 day early filing provision, the alien is not eligible for naturalization until he or she has reached the required five-year period of continuous residence."
This calculator always shows both dates: the earliest date you can submit Form N-400, and the anniversary date on which you actually become eligible. The 90-day window only moves the filing date earlier — it does not move up the day you meet the continuous residence requirement, and it has no effect on the physical presence requirement at all. Physical presence must be fully met, 913 days, as of the day you file.
What does this calculator not cover?
This calculator only handles the general naturalization path (INA 316(a)) and the spouse-of-a-US-citizen path (INA 319(a)). It does not cover N-470 preserved residence, military service paths (INA 328 and 329), INA 319(b) spouses employed abroad, VAWA or battered-spouse provisions, applicants under 18, anyone with a removal order or time out of status, or good moral character determinations. If your situation touches any of these, this tool will tell you so instead of guessing, and point you to uscis.gov.
Every rule and its USCIS source
This is the complete list of rules this calculator implements. Nothing else. Each row links to the government source it comes from.
| Rule | Threshold | Source |
|---|---|---|
| Continuous residence required (general path) | 5 years as a lawful permanent resident | P1 |
| Physical presence required (general path) | At least 30 months (at least 913 days) | P2 |
| Continuous residence required (spouse of a US citizen) | 3 years as a lawful permanent resident | P3 |
| Physical presence required (spouse of a US citizen) | 18 months (548 days is our derived figure, not a USCIS-published number) | P3 |
| Marital union required (spouse of a US citizen) | Married to, and living in marital union with, the US citizen for 3 years before filing | P3 |
| Day counting on a trip abroad | Both the departure day and the return day count as days present in the US | P2 |
| No presumption of a broken continuous residence | A single trip of 180 days or less | P1 |
| Rebuttable presumption of a break | A single trip of more than 180 days but less than 365 days | P1 |
| Automatic break in continuous residence | A single trip of 365 days or more | P1 |
| Early filing window | Up to 90 days before the continuous residence anniversary | P4, P7 |
| Where an absence is measured | Against the statutory period being tested, not the whole trip. Only the part of a trip that falls inside that period counts toward the 180 and 365 day thresholds | P1 |
| When the clock restarts after a break | A new statutory period begins on the date you returned to the United States | P1 |
| Earliest filing after an unrebutted break | Counting from the return date: 4 years and 6 months on the general path, 2 years and 6 months on the spouse path | P1 |
| Approved Form N-470 (preserved residence)Not checked by this calculator | Changes the analysis entirely. This calculator stops and refers you to USCIS instead of guessing | P1 |
| State or USCIS district residenceNot checked by this calculator | 3 months immediately before filing — you must check this one yourself | P1 |
P1–P4 and P7 refer to the USCIS Policy Manual and 8 CFR 334.2(b). This tool does not display or estimate filing fees — check the current amount on uscis.gov/g-1055 before you file, since it changes and a rejected application does not get its fee back.