Question about 1 drink and driving...What's the real limit?

If I go to dinner and have one beer/wine, then eat my food, hang out a bit and drive home, would I realistically get nailed if stopped? I know it's supposed to be zero tolerance but what's the actual limit according to cops? I mean, some desserts even have alcolohol. I understand the intention of the law but has it really removed the freedom to have just one drink to kick back?