The most common maximum size bag allowed is 62 linear (total) inches. A common size bag for checking through is: 27" x 21" x 14". Airline carriers will allow overweight, oversize or additional baggage for additional fees.
How do they measure luggage size?
The calculation is easy; just add the total of the length plus the width plus the height of the case to calculate its size in linear inches. You must include wheels and handles in your measurements. If you want to convert to centimeters, multiply the number in inches by 2.54.