For each day of stay, look back 179 days. Together with the day being checked, this forms the rolling 180-day window in which no more than 90 chargeable Schengen days may generally occur.
One shared Schengen total
The 90/180-day rule gives the 26 Schengen states a single shared allowance. Days in Spain, France and Poland all draw on the same 90, and leaving one country for another changes nothing.
The 90/180-day rule counts both boundary days
Arrival day and departure day are each full days. A trip from the 1st to the 5th is five days, not four. That single habit accounts for most miscounts.
The 90/180-day rule moves with the date
The 180-day window is rolling, not fixed. On any given day you look back 180 days and add up. Days drop out of the window as they age, which is why the same trip can be fine in March and a problem in January.
Important limitations
National long-stay visas and residence permits sit outside this count. Some nationalities have bilateral agreements that change the picture. If you hold a permit from a Schengen state, ask before assuming the 90 days apply to you.
Check against the official calculator
The European Commission publishes a calculator that applies the rule as the border authorities do. Use it for the trip you are about to book, not for the one you have already taken.
What to check
- Record all previous Schengen entries and exits.
- Check the number of days and entries printed on your visa.
- Consider residence permits and long-stay visas separately.
- Verify the current Schengen membership list.