DayWindow
How do you count 180 days in Schengen?
Backwards, from the day you are being checked. Never forwards from your first trip. That one direction is where most wrong answers come from.
The rule itself is one sentence: you may spend 90 days inside the Schengen area in any 180‑day period. The trouble is that almost nobody reads "any 180‑day period" the way a border officer does, and the difference is usually weeks.
The 180 days end today, not start today
Pick the day you want to know about: today, or the day you plan to fly. Count backwards from that day, 180 days. Everything inside that stretch counts. Everything before it does not.
So the window is not a period you are given at the start and use up. It is a ruler held against your recent past, and it slides forward with you. Tomorrow it covers a slightly different 180 days than it does today.
What counts as a day inside
The day you arrive counts as a full day, and so does the day you leave, no matter what time your flight is. An afternoon landing and a breakfast‑time departure are each a whole day. Days in transit through a Schengen airport count too if you pass through passport control.
This alone catches people out on short trips: four weekend breaks of three nights each are not 12 days, they are 16.
Count it by hand, once
The method
1. Write down the date you are checking, call it the check day.
2. Count back 180 days from it and write that date down too. That is the start of your window.
3. List every trip you took that touched that window, arrival and departure dates included.
4. Add up only the days that fall on or after the window's start date. A trip that began before it counts only from that date onwards.
5. If the total is 90 or under, you were inside the rule on that day.
Do it for the day you land and it tells you whether you may enter. Do it for the day you plan to fly home and it tells you whether that plan is legal. Those are two different sums, and both have to pass.
The three mistakes
Counting forwards. Taking your first entry date and adding 180 days gives a fixed window that resets, and no such window exists. It produces an answer that looks certain and is wrong.
Assuming the allowance refills in a lump. It does not. Each day you spent falls out of the window exactly 180 days later, one at a time, in the order you used them. That is worked through in detail in when your days come back.
Checking only today. Being inside the rule this morning says nothing about the day you fly home. Every extra day you stay changes the sum for the next one, so a plan has to be walked forward day by day, not checked once.
What the official calculator says about itself
The European Commission publishes its own short‑stay calculator. It is the same arithmetic, and it carries a line worth reading before you rely on any tool, ours included. In its own words:
“The calculator is a helping tool only; it does not constitute a right to stay for a period resulting from its calculation.”
Read on the Commission's calculator page, 11 August 2026.
Its newer sibling, the EES tool, carries two further warnings of its own, quoted in full in the official calculator, and what it does not count. That is true of every counter on the internet. A calculator tells you what the arithmetic says; the officer at the border decides what happens next. What a good one saves you is the by‑hand walk above, done correctly, every time you change a date.
Or let it count for you
The calculator on this site does exactly the five steps above, then keeps walking forward to find the last day you could stay. Put your trips in once and it shows the date you must be out by, when each day comes back, and how many. It is free, there is no sign‑up, and nothing you type leaves your own browser.