Snowbird Days Calculator (US Substantial Presence Test)
Enter your days for the last three years. The Substantial Presence Test weighs all of this year's days, plus one-third of last year's and one-sixth of the year before, against the 183-day line the IRS uses to treat you as a US tax resident. The four Form 8840 Closer Connection conditions are screened alongside it.
Where you stand this year
Top: your weighted total against the 183-day line. Bottom: this year's days against the most that keep you under the test, and the Form 8840 limit when all three of its facts are ticked.
Most days you can spend in each of the next five years
Each bar is the most days you could spend in the US that year without meeting the test, if you spend the full allowance in every year before it. Spend fewer days than a bar and the next bar rises by about one day for every three you skip.
How your weighted total is built
Each year's days times its weight. Only the weighted total is compared with the 183-day line.
| Year | Days | Weight | Weighted |
|---|
How this is calculated
The two-part test
You meet the Substantial Presence Test only if both are true: you were present at least 31 days in the current year, and your weighted three-year total is at least 183 days. Both conditions are set by statute. Source: IRS – Substantial Presence Test.
The weighted-day formula
weighted = (this year × 1) + (last year × 1/3) + (year before × 1/6). That is why steady visits of 120 days a year stay under the line (120 + 40 + 20 = 180), while 122 days a year adds up to exactly 183 (122 + 40.7 + 20.3) and meets it. The calculator counts in exact sixths of a day, so a total of exactly 183.0 always meets the test. Source: IRS – Substantial Presence Test.
Most days without meeting the test
For any year, the most days you can spend in the US without meeting the test is the larger of two numbers: 30, because fewer than 31 days can never meet it, and the most whole days that keep the weighted total under 183 once that year's two earlier years count at 1/3 and 1/6: most days = max(30, largest d with d + last year ÷ 3 + year before ÷ 6 < 183). With 150 days in each earlier year that is 107 (107 + 50 + 25 = 182), because 108 reaches 183. After very heavy years the 30-day floor is what applies: 366 days in each of the two earlier years carry in 183 weighted days on their own, yet 30 days still cannot meet the test.
Where you stand this year (chart)
The top bar is your weighted total against the 183-day line. It turns a neutral colour when you were in the US fewer than 31 days this year, because the total does not count then. The bottom bar is this year's actual days against the most that keep you under the test. With all three Form 8840 facts ticked, the band from there to 182 days is where you meet the test but the exception can still apply; from 183 days it cannot. Both bars run from 0 to 366 days, so 183 sits in the middle of each, and a weighted total past 366 fills the top bar. They measure different things: weighted days on top, calendar days below.
The next five years (chart)
Each bar applies the rule above to a future year, assuming you spend exactly the bar's days in every year before it: next year counts this year at 1/3 and last year at 1/6, the year after counts next year's bar at 1/3 and this year at 1/6, and so on. Spend fewer days than a bar and the next bar rises by about one day for every three you skip, because that year counts at 1/3 in the next one. The bars further on are not sure to rise: if you then use the higher allowance, it counts against the years after it. Within a few years the bars settle into a repeating 122, 122, 121 pattern: 122 days works in two years out of three, but not every year, because 122 every year reaches exactly 183 (122 + 40.7 + 20.3) and meets the test. 121 is the most you could spend every single year (121 + 40.3 + 20.2 = 181.5). The dashed Form 8840 line, shown when you tick all three facts, is the most days the exception allows (strictly fewer than 183). It only helps in a year when its facts hold and you file Form 8840 on time for that year.
What counts as a day
Any part of a day physically present in the US counts as a full day, so enter whole days (the calculator rounds a fractional entry up). Some days do not count: commuting from Canada for work, under-24-hour transit between two foreign points, days you could not leave due to a US medical condition, and days as an "exempt individual" (certain visa holders, who file Form 8843). Most Canadian snowbirds have no exempt category and count all days; this tool does not model excluded or exempt days, so subtract them from your entries yourself. Source: IRS – Substantial Presence Test.
Closer Connection Exception (Form 8840)
Even if you meet the test, you may be treated as a nonresident if you were present strictly fewer than 183 days this year, kept a tax home in a foreign country (Canada) all year, had a closer connection to that country than to the US, and took no steps toward a US green card. You must file Form 8840 on time to claim it, and it can cover a closer connection to at most two foreign countries. Sources: IRS – Closer Connection Exception, About Form 8840.
Treaty tie-breaker & Canadian residency
If you are a resident of both countries, the Canada-US treaty (Article IV) tie-breaker decides one treaty residence in sequence: permanent home, centre of vital interests, habitual abode, nationality, then competent-authority agreement. Your Canadian (CRA) residency is a separate, fact-based test resting on significant residential ties: a home in Canada, a spouse or partner, and dependants. This tool decides none of these. Sources: IRS Publication 597 (US-Canada Treaty), CRA Income Tax Folio S5-F1-C1.
What this doesn't do
It does not verify your dates, model excluded/exempt/medical days, assess your closer-connection facts, apply the treaty tie-breaker, handle first-year or dual-status elections, or determine Canadian residency. It also does not check US immigration limits on how long a Canadian visitor may stay, or your province's limits on time away before your health coverage is affected; both are separate rules with their own day counts. It is a day-count screen only. Confirm the rest with a cross-border tax professional.
Common questions
How many days can a Canadian snowbird spend in the US before becoming a US tax resident?
The IRS Substantial Presence Test counts all of your days this year, plus one-third of last year's days, plus one-sixth of the days from the year before. If that weighted total reaches 183 and you were in the US at least 31 days this year, you meet the test. Because of the weighting, spending roughly 120 days a year every year keeps a typical snowbird under the line (120 + 40 + 20 = 180), but 122 days every year adds up to exactly 183 and meets the test.
What is the Substantial Presence Test formula?
Weighted days = (days present this year x 1) + (days last year x 1/3) + (days the year before x 1/6). You meet the test if the weighted total is 183 or more AND you were present at least 31 days in the current year. Any part of a day physically in the US counts as a whole day.
What is the Closer Connection Exception (Form 8840)?
Even if you meet the Substantial Presence Test, you can be treated as a nonresident by filing IRS Form 8840 if you were present strictly fewer than 183 days this year, kept a tax home in Canada all year, had a closer connection to Canada than to the US, and took no steps toward a US green card. The form must be filed on time to claim the exception.
Does meeting the US test change my Canadian tax residency?
No. Canadian (CRA) residency is a separate, fact-based test that turns on significant residential ties: a home in Canada, a spouse or partner, and dependants. If you are a resident of both countries, the Canada-US tax treaty tie-breaker in Article IV decides a single treaty residence. This calculator only screens the US day-count test.