If your luggage is 1 kg overweight on an international flight, then the airlines can charge you with an excess baggage fee at the airport check-in counter. This additional fee that you will have to pay depends on the airline and the specific location route.
Several airlines do offer discounts when you buy excess baggage online in advance. This can be quite cheaper than paying for it at the airport. This can also save you time as you don’t have to wait for the baggage at the airport.
Several factors determine how much you will have to pay for overweight luggage. These include the airlines, the route distance, and how overweight the bag is. On an average, the range can turn into $50 to $100 per bag for some extra kgs.