There are too many variables for anyone to answer that for you. What countries are you going to? Big cities or small towns? Do you picnic with food from the grocery store, do you eat at modest restaurants, or do you splurge? Do you have to have beefsteak at every meal or do you try local specialties?
I travel mostly in Germany and surrounding countries, spend 85% of my time outside of big cities, sometimes grab a sandwich and a drink on the go, but usually eat at least one meal a day in sit-down restaurants, eat like a German (schnitzel, not steak), and enjoy the local beer. Not including breakfasts, which are included with my room, I consistently average 20€/person per day for food, drinks, tips (I give it in euro because that has stayed the same, the amount in dollars varies with the exchange rate.
But I agree with the previous poster. Use the number for budgeting purposes only. Use cash from the ATM. Don't bring US dollars; they will be hard to exchange and the rate won't be very good. Get a few hundred dollars in euro (or whatever currency they use where you are going) from the bank before you leave.
Be sure to notify the card company before you leave or you might find the card "frozen". Know what your daily limit is in the local currency. Once a bank lowered my limit from $500 to $300 between trips. When I tried to take out the equivalent of $500, all the ATM "said" was "call your bank".