I was told a cat carrier should be large enough the cat can stand fully upright, and wide enough they can turn around without too much difficulty! I usually put a towel in the bottom for grip, but bath mat and towel sounds even better!

[–] aramis87@fedia.io 2 points 11 hours ago

Ours is an old carrier. The interior dimensions are 16 inches tall, 14 inches wide, and 24 inches long. Our cat was maybe 14 inches tall, but of course she wouldn't want to stand fully upright and either bang her head on the roof, or constantly brushing her ears against it. Plus the bath mat and towel 'raised' the floor a bit. And sometimes when you scream, you just want to throw your head back and let go!

I like the bath mat because I can suction it to the bottom of the carrier, so neither she nor the towel slide around like they would on plain plastic or metal.