As every parent knows, going out -- like on a real grownup date -- gets a lot more expensive when you have little kids in the house. On top of the exorbitant price of movie tickets, or the cost of a meal, moms and dads fork over serious cash for childcare -- unless there's a doting grandparent (or other family member) they can impose on.

But once you've done the hard work of finding someone you trust to watch your little angel(s), how do you know how much to pay? Online babysitter-booking service UrbanSitter -- which helps parents in 13 cities across the country find potential sitters through social media and online reviews -- has published an infographic illustrating average hourly rates across the country, based on recent on-site user transactions.

Babysitters in all nine cities included in the infographic earn more than the federal minimum wage of $7.25 for babysitting a single child (the lowest average hourly rates are in St. Louis; the highest are in Manhattan and suburbs of San Francisco, where sitters make more than $15). Some New York babysitters caring for three children at a time might even make more than $20 per hour. The overall average hourly cost for babysitters in all cities is $12.75.

Other sites, like Sittercity.com and Care.com, offer alternative (and seemingly more modest) rate calculators. Care.com recommends $12.50 per hour for a single-child sitter in New York City; Sittercity.com recommends $14.50.

See UrbanSitter's infographic here (just don't show it to grandma -- she'll demand a raise):

urbansitter infographic