A multiple-entry Schengen visa may allow more than one border crossing during its validity period, but it does not automatically allow an unlimited stay. Travellers must distinguish the visa validity dates, the authorised duration shown on the visa and the general 90/180-day calculation where it applies.
Multiple entry does not mean unlimited days
The word MULT concerns the number of permitted entries. It does not remove the stay-duration limit. Several short trips may still be counted together inside the same rolling 180-day window.
Visa validity and duration of stay are different
The dates showing when a visa may be used are not necessarily the number of days a traveller may remain. Always check the visa sticker, including its duration-of-stay field, and verify personal conditions with the issuing authority.
Example with three separate trips
If a traveller completes stays of 20, 25 and 30 days and all of those days fall inside the relevant rolling 180-day window, the planning total is 75 days. Leaving between the trips does not erase the earlier days.
How to test multiple trips
Enter every completed stay separately in the Schengen 90/180 Calculator, then add the proposed trip as a planned stay. The result is an educational date-planning estimate and cannot interpret the legal effect of an individual visa sticker.
When the calculator is not enough
Do not rely on a general calculator to interpret a limited-duration visa, territorial restriction, residence status, bilateral arrangement or an individual decision. Check the visa itself and use official or qualified guidance for your circumstances.