Why is tipping based on a percentage of the meal rather than a fixed charge for different levels of service?  Say the wage is $12 per hour and a living wage is $25 per hour, then there is another $13 per hour to cover.  If the person is busy 50% of the time, that is $26 to make up.  That works out to 43 cents per minutes round up to 50 cents per minutes.  Figure out how much actual time the server spent on you in minutes and divide by two to get the tip.  If the salary is higher the tip should be lower.