Obviously the exact amount varies by where you live, etc...but I know with my son I spent $150 a month on formula alone (I wasn't able to breast feed) and then you add in any solid foods, diapers, a larger house to accommodate the extra person, any child care expenses, etc. it's definitely a good chunk of money. I think every state differs, and I'm sure every country does, but I know in Wyoming child support is figured on 25% of the non-custodial parent's gross income and this seems to be fairly standard throughout the US. If you're in the US and haven't done so, you can go to child support enforcement through DFS to get a standard amount set. Even if he's not employed right now or not a W-2 employee, once that's set by the state then it doesn't go away until he pays it...he'll get no tax returns, ineligibility for a lot of benefits, etc. until he's paid to current on support obligations.