What "linear inches" means
Linear inches is the simple sum of a bag's three outer dimensions: Linear inches = Length + Width + Height. Airlines use this single number as a quick way to size checked and carry-on baggage without having to check three separate measurements against three separate limits. Measure each dimension at its longest point — including wheels, handles, and any external pockets — since that is how most airlines measure at the gate or check-in counter.
The formula
There is nothing to weight or scale: you just add the three numbers together.
- Length — the longest side of the bag, in inches.
- Width — the second dimension, in inches.
- Height — the depth or thickness, in inches.
- Total linear inches = Length + Width + Height.
For example, a bag measuring 24 × 16 × 10 inches has 24 + 16 + 10 = 50 linear inches. That total is what gets compared against an airline's posted limit — not any single dimension on its own.
Typical airline limits (check your carrier)
Baggage rules vary by airline, fare class, and route, but a few figures are common across most U.S. domestic carriers:
- ~45 linear inches — a common carry-on sizing guideline (frequently expressed as 22 × 14 × 9 inches, which sums to 45).
- 62 linear inches — the standard checked-bag limit for many airlines before extra fees apply.
- ~80 linear inches — where "oversized" surcharges commonly start.
- ~115 linear inches — a typical ceiling beyond which many airlines will not accept the bag at all.
Always confirm the exact number with your airline before you travel, since limits and fees change and can differ for international flights.
Why the metric-side number matters too
Outside the U.S., baggage policies are frequently stated in centimeters rather than linear inches (a metric equivalent to 158 cm, roughly matching 62 linear inches, is common). Converting your total by multiplying by 2.54 lets you compare against either style of limit.