Bag Calculator

What Is the Bag Calculator?

The Bag Calculator computes the volume of a bag from its three external dimensions and checks the result against published carry-on size limits for major airlines. Travellers, packing optimisers, and frequent flyers use it to figure out whether a specific bag qualifies as a carry-on before they arrive at the airport, and to compare the usable space across different luggage options. According to the International Air Transport Association cabin baggage guidelines, carry-on dimensions and allowances vary significantly across carriers, and non-compliance at the gate often results in fees that exceed the cost of checking the bag at booking.

Volume and linear dimension are the two measurements that determine carry-on compliance. Volume (length times width times height) expresses the total packing space in litres or cubic inches, which manufacturers use to describe luggage capacity. Linear dimension (the sum of all three measurements) is used by airlines as an alternative compliance check because it captures overall bag size in a single figure without requiring separate checks of each dimension. A bag can have a slightly larger height if it compensates with a smaller width, as long as the total linear dimension stays within the airline's limit. Given this, the calculator provides both measurements so you can verify compliance under either rule that your airline applies.

How Airline Carry-On Size Limits Work

Airlines specify carry-on limits as three separate maximum dimensions (length, width, and height) or as a maximum linear dimension, or both. The most widely cited US standard is 22 by 14 by 9 inches (56 by 36 by 23 cm), which is used by American Airlines, Delta, United, and many other major carriers. This limit includes all protrusions: wheels, telescoping handles, exterior pockets, and compression straps. A bag whose body measures 21 by 14 by 9 inches but whose wheels add 1 inch to the height still measures 22 inches in height and must fit within the 22-inch limit total.

Soft-sided bags present a particular compliance challenge because their dimensions change based on how full they are. A soft bag that is compressed when empty may expand to 2 or 3 inches beyond its nominal size when packed to capacity. That said, gate agents assess the bag in the condition you present it, which means a fully packed soft bag that exceeds the sizer template will be checked regardless of its labelled size. As a result, measuring your bag fully packed to the level you intend to travel is the only reliable compliance check, and the calculator should be used with your actual travel dimensions rather than the manufacturer's stated capacity dimensions. The US Department of Transportation Fly-Rights guide confirms that airlines are entitled to enforce their published size limits at any point during boarding.

Carry-On Size Limits by Major Airline

Carry-on allowances vary by airline, route, and fare class. The table below shows the standard carry-on limits for major US carriers and selected international airlines. All measurements include wheels and handles.

Packing Efficiency and Volume Comparison

Understanding bag volume in litres helps when comparing luggage options with different shapes. A bag labelled 40 litres and a bag labelled 40 litres from a different manufacturer may have very different proportions: one might be tall and narrow, the other short and wide. The packing utility of each depends on the items you carry. Tall, narrow bags suit rolled clothing and bottles; wider, flatter bags suit laptops, documents, and flat items. The volume calculation in the bag calculator allows you to verify that a bag's stated capacity matches its actual dimensions, which can differ from manufacturer claims for bags measured using internal rather than external dimensions.

Linear dimension is particularly relevant for checked baggage. Most airlines allow checked bags with a linear dimension of up to 62 inches (158 cm) before charging oversize fees. A standard large checked suitcase measuring 28 by 18 by 14 inches has a linear dimension of 60 inches, leaving 2 inches of margin. A bag measuring 30 by 19 by 14 inches has a linear dimension of 63 inches and would incur oversize fees on most carriers. What is more, oversize fees charged at the airport are often significantly higher than those disclosed at booking, making pre-trip dimension verification a straightforward way to avoid unexpected costs at check-in.

Accuracy and Limitations

The bag calculator is mathematically exact for the dimensions entered. Its practical accuracy depends on how carefully the bag dimensions are measured. Soft-sided bags must be measured when fully packed to get a meaningful compliance estimate; empty measurements may be 10 to 20 percent smaller than the packed size. The airline size limits shown in the calculator reflect published policies as of the most recent update, but airlines change their carry-on policies periodically. Always verify the current policy directly on your airline's website before travelling, particularly for international routes and budget carriers where carry-on policies change more frequently.

The calculator does not account for overhead bin availability, which varies by aircraft type and how full the flight is. Even a bag that meets the size limit may need to be gate-checked on a small regional aircraft with limited overhead bin space. The calculator also does not include weight limits, which are enforced separately from size limits by most airlines and can be a binding constraint on international carriers that enforce 7 to 10 kg carry-on weight maximums. For comprehensive travel compliance, both the size check from this calculator and a physical luggage scale check are needed before departure.

The Most Common Carry-On Bag Measurement Mistake

The mistake I see most often is measuring the bag body without accounting for wheels, handles, and exterior pockets, and then being surprised at the gate when the bag fails the sizer template. A hard-sided 20-inch spinner, where 20 inches refers to the bag body height, typically measures 22 to 23 inches total once wheels and the top handle are included. With that in mind, always measure your bag in travel configuration with wheels extended downward and the handle retracted, placing the tape measure from the bottom of the wheels to the top of the bag, and from side to side across the widest point including any external pockets. This mistake turns up most consistently when travellers buy bags based on the manufacturer's stated size (which often refers to internal or body-only dimensions) without confirming the full external travel dimensions against their airline's specific sizer limits.