What this calculator works out
This calculator multiplies three dimensions to give a bag's volume in litres.
Volume is useful for comparing bags and useless for satisfying an airline. Airlines specify maximum dimensions, not maximum volume, so a compliant volume in the wrong shape still fails.
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Before you measure
- Measure the external dimensions including wheels, handles and any external pockets. Airline sizers measure the whole bag.
- Airline cabin bag limits vary substantially between carriers, and several distinguish a small underseat bag from a larger cabin bag carrying a fee.
- A soft bag can be squeezed into a sizer; a hard case cannot. That difference matters more than the stated capacity.
- Weight limits apply separately and independently. A compliant size can still be overweight.
A 44 litre bag measuring 55 by 40 by 20 cm fits most cabin allowances. The same 44 litres shaped 70 by 40 by 16 cm fits none of them. Airlines enforce with a rigid sizer, so the longest dimension is what fails — which is why bags are sold quoting dimensions first and capacity second.
How this calculator works
Three dimensions multiplied and converted:
Litres = length × width × height ÷ 1,000
All dimensions in centimetresDividing by 1,000 converts cubic centimetres to litres. The result is the volume of a rectangular box — a bag with curved sides or a tapered shape holds less than its external dimensions suggest, which is the opposite of the wheelie bin case where the box overstates capacity for the same reason.
Worked example: a cabin bag
Using the default figures — 55 by 40 by 20 cm:
- Volume: 44 litres
Those dimensions are a common cabin bag standard and 44 litres is a realistic capacity for a week away. But several budget carriers restrict free cabin baggage to a much smaller underseat bag — commonly around 40 by 20 by 25 cm, or 20 litres — with anything larger carrying a fee. Checking the specific carrier's limits before buying a bag saves more than any packing technique.
Common mistakes
- Measuring without wheels and handles. Airline sizers include them.
- Comparing bags on volume alone. Dimensions are what get enforced.
- Assuming allowances are consistent. They vary substantially between carriers.
- Forgetting the weight limit. It applies independently of size.
- Buying a bag before checking the airline. The allowance should determine the bag.
Frequently asked questions
What is a typical cabin bag allowance?
There is no standard, and that is the practical problem. Many full-service carriers allow around 55 by 40 by 20 cm plus a personal item; several budget carriers include only a small underseat bag in the base fare, with a larger cabin bag as a paid extra. The carrier's own page for your specific fare is the only reliable source.
Does the weight limit apply to cabin bags?
Usually, and it varies from around 7 kg to 10 kg or more. Some carriers weigh cabin bags at the gate and some rarely do, which makes it an inconsistent risk rather than an absent one. Where a bag is close to the limit, moving heavy items into a coat or personal item is a common practical response.
How do I fit more in?
Packing cubes and rolling rather than folding both help modestly. The larger gains come from taking less — laying out everything and removing a quarter of it is the technique that consistently works. Wearing the heaviest items on the plane shifts weight out of the bag without reducing what you take.
What if my bag is too big at the gate?
It is usually taken into the hold, with a fee that is substantially higher than pre-booking hold baggage. Gate charges are among the most expensive per kilogram of anything in travel. Where a bag is marginal, paying in advance is almost always cheaper than being charged at the gate.
Is what I enter stored?
No. Measurements are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — air passenger rights, baggage rules and prohibited items
- MoneyHelper — avoiding unexpected travel charges
Sources are checked at publication and can change — how I choose and check references.