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The "tooth fairy" gave $3 per tooth on average to children this year, up 15 percent from last year, according to a survey by credit card company Visa.

Visa also released a free app and online tool, the Tooth Fairy Calculator, that determines how much children in comparable households are receiving from the Tooth Fairy, based on demographics like age, gender, home state, income, and education levels.

The calculator was released as part of Visa's free financial education program, Practical Money Skills for Life.

It's unclear how exactly Visa is coming up with its guidance and if kids who live in more expensive areas should get more money from the tooth fairy, especially if she has to pay expensive rent or other cost of living considerations.

Plugging in a male parent's age of 33 living in Illinois with a college education and making $75,000 yields a $2 gift from the tooth fairy.

Change the parent's gender to female and the kid gets lucky with a $3 gift from the tooth fairy.

Then change the state of residence to New York and you get a less-valuable tooth for a gift of $1.

The Visa survey was conducted from July 13 to 17 through 2,000 telephone interviews with a random sample in cooperation with GfK Roper's Omnibus Service "OmnitTel." The margin of error was +/- 4 percentage points

Here's how much the tooth fairy gave all the other kids, including those lucky ones who found Abraham Lincoln under their pillows:

Less than a dollar: 3 percent of those surveyed, down from 7 percent last year

Exact $1: 30 percent, up from 29 percent last year

Between $2 to $4: 13 percent, down from 18 percent last year

Exactly $5: 18 percent, same as last year

More than $5: 8 percent, up from 3 percent last year