How many cats and dogs are killed each day due to not enough space in kennels?

hundreds over thousands over millions over trillions over billions

Not quite, an estimated number from the Humane Society of the United States (HSUS) of cats and dogs euthanized each year by shelters is 3-4 million, and it is widely accepted that altogether, 9.6 million dogs and cats are euthanized each year. It is difficult to pinpoint an exact amount because there are so many cases.