Three outer dimensions in cm—compare sum to a carrier limit (default 158 cm; change to match your airline).
The tool adds the three edge lengths in centimeters and compares the sum to your stated airline limit (cm). It shows whether the sum is within the limit or by how many centimeters it exceeds it; carrier rules (wheels/handles) are not modeled.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.