The 'One That Got Away' singer - who married the British funnyman last October - says the couple are keen to start a family and knows Russell will step up to the responsibilities of parenthood.
She said: "I would love to have children. I think that's one of the reasons you get married. Especially to the person that you marry. You think, that person is going to be a good partner, a good parent.
"But I'm not sure it's yet. We'll see, ya know."
Katy also says the number of children she has will depend on how much pain she experiences when she gives birth to her first child.
She told TV talk show host Ellen Degeneres: "If it doesn't hurt the first time. I'll keep popping them out."
Katy has made no secret of her desire to become a mother and has said her children would always come before her career.
She said: "I want to have kids! I'm totally fine with saying that. I think some people are worried it's going to ruin their career, but I want to live a full life."