Article — Linear Inches Calculator
Linear inches calculator: airline luggage size limits, demystified
Linear inches is the sum of a bag's length, width, and height in inches. It is the single number airlines use to classify baggage. The carry-on standard at most US carriers is 45 linear inches (22 x 14 x 9 in). The checked-baggage standard worldwide is 62 linear inches (158 cm), set by IATA Resolution 743 and adopted by virtually every major airline since the 1990s. Bags between 62 and 80 linear inches usually trigger an oversize fee of $100 to $200 per leg in 2026, and bags above 115 linear inches are refused outright by most carriers.
The calculator above adds your three dimensions and immediately shows whether your bag clears the carry-on limit, the checked limit, or neither. It also converts between inches and centimeters in real time, so you can match either the US imperial standard or the IATA metric standard without doing the math twice.
What are linear inches?
Linear inches is a one-dimensional summary of a three-dimensional object. Take the length, width, and height of a suitcase, add them together, and the resulting number is the linear inches. A 22-by-14-by-9 inch carry-on equals exactly 45 linear inches; a 30-by-20-by-12 inch checked bag equals 62 linear inches. The metric equivalent is sometimes called linear centimeters and uses the same arithmetic with the metric figures.
Airlines adopted linear inches because cargo holds and overhead bins are bounded boxes. A bag that exceeds the longest dimension cannot fit no matter how well-packed it is. The single linear-inches number captures that constraint elegantly: a bag with one very long side and two short ones will fail the linear-inches check even if the volume is modest.
The 158 cm (62 linear inches) standard for checked baggage was formalised by IATA Resolution 743 and has been the de facto worldwide rule since the 1990s. Before standardisation, each airline published its own measurements, and passengers routinely arrived at the gate with bags that fit one carrier and not another. The standard reduced gate disputes by an order of magnitude.
The linear inches formula
The formula is pure addition. Linear inches = Length + Width + Height. There is no rounding, no weighting, no exclusion. Every external dimension counts, including wheels, handles, exterior pockets, and any bulges from rigid frames or expansion zippers.
Linear inches = L + W + H (inches)Linear cm = L + W + H (cm)62 LI = 158 cm (IATA checked standard)Carry-on linear inches limits
Most US carriers cap carry-on bags at 45 linear inches, equivalent to the 22 x 14 x 9 inch dimensions stamped on essentially every "standard" suitcase. Southwest, Spirit, and Frontier are generous: they allow up to 50 linear inches (24 x 16 x 10 inches). International carriers tend to be tighter: British Airways uses 56 x 45 x 25 cm (51 LI), Lufthansa 55 x 40 x 23 cm (46 LI), Emirates 55 x 38 x 20 cm (44 LI).
Gate agents enforce carry-on limits at boarding using a metal sizer template. If the bag does not slide into the template, it gets gate-checked — usually free on most US carriers, but the inconvenience of waiting at baggage claim erases the time savings.
Checked baggage linear inches
Checked baggage uses the IATA standard of 62 linear inches (158 cm). Below that, your bag flies free or at the standard checked fee. Between 62 and 80 linear inches (roughly 158 to 203 cm), it counts as oversize and triggers a fee. Above 80 linear inches it counts as cargo on most airlines and requires special handling. Above 115 linear inches (292 cm) most carriers refuse the bag entirely.
American, Delta, and United charge $200 each way for bags between 62 and 80 linear inches. A round trip with one oversize bag adds $400 to the ticket. Repacking into two normal bags costs $70 to $100 on most fares, less than half the oversize hit.
Linear inches limits by airline
The 62-linear-inch checked-baggage standard is nearly universal, but carry-on dimensions and oversize policies vary. The reference table above lists current figures for the largest US and European carriers. A few patterns hold across the industry:
- 62 LI = the universal checked-baggage standard
- 45 LI = the dominant US domestic carry-on size (22 x 14 x 9 in)
- 50 LI = Southwest and budget carrier carry-on allowance
- 80 LI = oversize cap on Spirit and Frontier with paid upgrade
- 115 LI = absolute refusal threshold on most US carriers
- 23 kg / 50 lb = weight limit that runs parallel to size limit
How to measure your bag correctly
Lay the bag on a flat surface with the handle retracted and wheels facing out. Measure length from front to back at the widest point, width from side to side, and height from the floor (or wheel bottom) to the top edge. Use a soft tape measure rather than a ruler, since suitcases bulge slightly when packed.
Measure a packed bag, not an empty one. Soft-sided luggage expands by 1 to 2 inches in each dimension when loaded, which can push a 45-LI carry-on past the gate sizer. If you plan to fill the bag, add a couple of inches to each dimension before running the calculator.
Converting linear inches to centimeters
Multiply linear inches by 2.54 to get linear centimeters. The two main reference points: 62 linear inches equals 157.5 cm (airlines round up to 158 cm), and 45 linear inches equals 114.3 cm (115 cm in airline policy). Going the other way, divide centimeters by 2.54 to convert to inches.
European and Asian airlines almost always quote in centimeters; US and Caribbean carriers in inches. The calculator above accepts either unit and shows the conversion alongside the answer, so the unit difference between booking sites does not become a sizing mistake at the airport.
Common linear-inches mistakes
The five most common errors: measuring inside the bag instead of outside (the manufacturer's "interior capacity" number is always smaller than the airline-relevant external dimension), excluding the wheels (wheels add 1 to 2 inches), forgetting to extend or retract the handle as the airline specifies, ignoring exterior pockets and bulges (they count), and confusing weight limits with size limits (a 62 LI bag at 65 lb still incurs an overweight fee). Measure with the bag packed, the wheels included, the handle retracted, the tape soft. Round up rather than down.