The IATA (International Air Transport Association) states the maximum size to be 56 x 45 x 25 cm. But many airlines deviate from this (for example, Brussels Airlines has a maximum size of 55 x 40 x 23 cm). So before you leave, check the company website of the airline you are flying with to prevent unpleasant surprises at the gate. Nowadays, you can often take an additional accessory along with your trolley or travel bag, such as a handbag or laptop bag. Double handy!
What you can bring depends on the airline with which you are flying. Be sure to check the website before you leave. In principle, you can take everything with you, except:
As far as liquids are concerned, you are usually allowed to take up to a maximum of 100 ml of each item on board. Store them all in a transparent bag to ensure you can get through the security check quickly. Anything you buy in the tax-free zone can also be taken on board in your hand luggage. There are some items that must be taken on board as hand luggage and are not allowed in your checked baggage, these include electronic devices with lithium batteries (laptop, mobile phone, tablet).
The weight of your hand luggage depends on the airline with which you are flying. Be sure to check the website before you leave. For Brussels Airlines, your travel bag or trolley must not exceed 12 kg (which is quite generous compared to other airlines such as Ryanair and Transavia who have a maximum weight of 10 kg). You can often also take an additional item such as a handbag or laptop bag.
Hand luggage is the baggage you are allowed to take with you on the plane i.e., the baggage you don’t have to check in at the counter. You only need do that with checked baggage. Backpacks, travel bags, trolleys, laptop bags or camera bags: as long as they fit within the maximum dimensions and do not contain prohibited items (check the website of your airline), they can be taken on the plane as hand luggage!