How do I know if a luggage or suitcase is too big? I get this question often when selling luggage on our sales floor at Luggage Base. Some times customers come in with a tape measurer and says they are looking for the biggest luggage that can be checked through the airlines. Rule of thumb is 62 linear inches. That is when you add up length + width + depth = linear inches. Now to be honest, the airline employees at the counter rarely measure a bag or luggage unless they think it is extremely large and wont fit on the conveyor belt. At that point they will measure it and usually assess a fee. The reason for this is since it wont fit on the conveyor belt, someone has to hand deliver the bag to the transporter car that takes it to the plane. So if you are looking at large bags don't worry too much if its a couple inches off the airlines checked bag requirements. That being said, always refer to the airlines website for checked bag measurements and restrictions.