Comparisons
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30 vs 36 inch dog crate: which one?
30" covers 26–40 lb, 36" covers 41–70 lb on both MidWest's and PetMD's charts.
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36 vs 42 inch dog crate: which one?
The 36" is for 41–70 lb dogs, the 42" for 71–90 lb. Length and height decide close calls.
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Crate size by weight vs by measurement: which to trust
Every chart starts with weight. PetMD's own chart adds length and height limits, and says the measurement wins.
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Dog crate size chart by weight and breed
Seven standard crate lengths, the weight each one fits, and the breeds that usually land there. Then measure, because PetMD says measurements win.