US Substantial Presence Test Calculator
The IRS decides US tax residency for non-citizens with a weighted three-year day count: this year's days, plus 1/3 of last year's, plus 1/6 of the year before's. Reach 183 (with at least 31 days this year) and you meet the Substantial Presence Test. Enter your days to see exactly where you stand — and how many more days are safe.
1 · Your days in the US
Count every day you were physically present in the United States for any part of the day — arrival and departure days included. Leave out exempt days (see the notes below the calculator).
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2 · The result
- 31-day prong: 0 days this year — not met (30 or fewer, so the test cannot trigger)
- 183-day prong: weighted total of 0 — under 183
You do not meet the test for 2026. Given your two prior years, you can be present up to 182 days this year and still stay under it.
How this calculator counts
- A day is any part of a day physically present in the US — arrival and departure days both count, unless a specific exclusion applies.
- Fractions are not rounded. The exact total of current + prior/3 + second-prior/6 is compared against 183, per 26 U.S.C. §7701(b)(3).
- Both prongs must be met. Fewer than 31 days in the current year means the test cannot trigger, no matter how heavy the prior years were.
- The safe-days figure is the most current-year days that keep the weighted total under 183 (never below 30, since 30 days always fails the first prong).
A worked example
The classic IRS example: 120 days in each of three consecutive years. The weighted total is 120 + 40 + 20 = 180 — under 183, so the test is not met, and the pattern can be repeated indefinitely. Push each year to 122 days, though, and the total becomes 183 — resident. The margin between a sustainable snowbird routine and US worldwide taxation is two days a year, which is why the count is worth doing precisely rather than by feel.
Remember the exceptions: exempt-individual days (students, teachers, diplomats), medical-condition days, and the closer-connection and treaty escapes. The full rule guide covers them.
Frequently asked questions
You are a US tax resident for a year if you were present at least 31 days that year AND your weighted total reaches 183: all of this year's days, plus one-third of last year's, plus one-sixth of the year before's. Meeting both prongs generally makes you resident from your first day of presence that year (up to 10 days of presence can be disregarded in some cases).
No. The Treasury regulations say fractional days from the 1/3 and 1/6 multipliers are not rounded to the nearest whole number (Treas. Reg. §301.7701(b)-1(c)(1)), so this calculator compares the exact total against 183. 120 days in each of three years gives exactly 180 (120 + 40 + 20), which is under 183.
Days as an exempt individual (students on F/J/M/Q visas generally for up to 5 calendar years, teachers/trainees on J/Q generally for 2 calendar years in any 6, diplomats), days you couldn't leave due to a medical condition that arose in the US, days in transit under 24 hours, and regular commuting days from Canada or Mexico. These require Form 8843 in most cases.
Two main routes. The closer connection exception (Form 8840): under 183 actual days in the current year, a tax home in another country, and a closer connection to it. Or a tax treaty tie-breaker if your country has a US treaty. Both must be actively claimed — they don't apply automatically.
The IRS treats you as a US tax resident: you're taxed on worldwide income and file Form 1040, with FBAR and other reporting obligations potentially attaching to your non-US accounts. If that's not what you intended, the safe play is managing your day count before you cross the line.
Your entries are saved only in your own browser (localStorage). We do record usage events that aren't linked to your name, including the day total and the result category the calculator shows, but not the dates of your trips.
This rule is tracked automaticallyin
Bounded
- Automatically tracks your days for this rule
- Shows your weighted day count against the 183-day line
- Records border-crossing days in both countries
- Runs alongside your other visa, tax, and residency rules
Sources
For information only. This calculator is a planning aid based on publicly available rules, not tax, legal, or immigration advice. Border officers and tax authorities make the final call — always confirm with the official sources linked above and a qualified professional before acting.