SAS measures your personal item in litres rather than inches. The underseat allowance is 18 litres, which is an unusual way to state it and a useful one once you understand SAS baggage rules.
Volume is what actually determines whether a soft bag fits under a seat. Three dimensions do not capture a bag that squashes.
The cheapest fare has no cabin bag
SAS Go Light does not include a cabin bag at all. You get the 18 litre underseat item and nothing above it.
A cabin bag can be bought separately on that fare. Unlike some carriers, SAS does let you add one.
Economy Standard and Flex include the cabin bag as part of the fare. So do Premium and Business.
The 8 kilogram limit applies to one bag only
The cabin bag is 55 by 40 by 23 centimeters, roughly 21.7 by 15.7 by 9.1 inches, at 8 kilograms. That weight covers the cabin bag alone.
The 18 litre underseat item does not count toward it. SAS publishes no separate weight limit for that bag.
This is more generous than it first appears. Finnair applies its 8 kilograms across both bags combined.
Overweight fees are published, in bands
On North America routes, a bag from 23.1 to 28 kilograms costs $90. From 28.1 to 32 kilograms it is $160.
Bags over 158 centimeters in total are charged at those same rates. Oversize and overweight share one price list.
Published bands are rare among European carriers, most of which quote per itinerary. SAS baggage rules are unusually transparent here.
Checked allowance moves with the ticket
Economy Light includes no checked bag. Economy Standard and Flex include a carry-on plus checked allowance.
Piece weights run from 23 kilograms up to 32 kilograms depending on ticket type. Premium and Business sit at the top of that range.
The 158 centimeter size cap applies throughout, so only weight and piece count change.
How SAS baggage rules compare
The 55 by 40 by 23 cabin size matches Lufthansa, SWISS and Austrian. Most of northern Europe uses this frame.
The stripped Light fare is also standard across the region. What sets SAS apart is the litre based underseat measure and the published fee bands.
Our European carry-on size guide lays the region out together.
Choosing a bag for 18 litres
Eighteen litres is a small daypack, not a full backpack. A 20 litre bag will usually still fit if it is soft and not overstuffed.
Rigid bags are judged on their actual footprint. A hard sided case near 18 litres may not slide under the seat at all.
If you are flying Go Light, this bag is your entire allowance. Choose it before you book rather than after.
The bottom line
SAS baggage rules are conventional on size and clearer than most on fees. The two things to watch are the missing cabin bag on Light and the 18 litre underseat limit.
Confirm the dimensions in the size checker, and see how we verify these pages.