How this calculator works
Measure the standing dog without including the tail length, and use the tallest head or upright-ear point. Add the selected clearance to length and height separately. The 2 to 4 inch rule is a household shopping guide. Interior space can differ substantially from the advertised exterior dimensions. Width and door opening still need a physical fit check.
Formula
Interior length = measured dog length + clearance. Interior height = measured dog height + clearance. Reverse mode subtracts the same clearance. One inch = 2.54 cm exactly.
Worked example
For a 60 cm long and 40 cm tall dog, adding 3 inches gives starting interior dimensions of 67.62 cm long and 47.62 cm high.
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Frequently asked questions
Is this an airline-approved size?
No. Airlines apply carrier construction and animal measurement requirements. Confirm directly with your airline.
Should I include the tail?
Use nose to tail base with this clearance rule. Follow the manufacturer's instructions if they specify a different measurement.
What about a growing puppy?
Consider adult dimensions and an appropriate divider. Check comfort frequently as the puppy grows.