You probably don't know Karl Ebert, but he may have helped you with some of the biggest financial decisions of your life.
Whether it's buying a home, figuring out how much you need to save for your kid's education or when to claim Social Security benefits, Ebert has an online financial calculator for you.
"Each tool needs to answer a specific question or solve a particular problem. To do that well, the calculator should ask for just the right amount of information to create a useful answer without requiring hours of inputs," he said.
His one-man company has created more than 450 online tools that are licensed to more than 10,000 websites and financial institutions, including the AARP, American Funds, Bankrate, Navy Federal Credit Union and Thrivent Financial.
It all started with a Roth IRA in 1998, which had only become available to investors a year before.
Ebert, a business consultant back then, wanted to figure out if it was worth converting his traditional IRA to a Roth. So he made a simple calculator to find the answer.
After he had created the calculator, he put it on his website, Dinkytown.net. Ebert, who lives in the Dinkytown neighborhood of Minneapolis, had originally envisioned his site as a local online portal, a sort of early predecessor of Yelp.
That idea didn't pan out, but people started to notice the financial calculators he added to the site. One fan sent Ebert a $250 check to license his calculator for another website.
Ebert's side hustle was transformed into a full-time business when Minneapolis-based U.S. Bank ordered a suite of tools from him in 1999. "I was in the right place at the right time," he said. (Now U.S. Bank uses online tools made by S&P Capital IQ Financial Communications.)
Ebert, 48, mainly works alone in his home office, though he sometimes hires developers to help with big projects. He is married, but preferred not to discuss his personal life.
"I enjoy solving problems and I've always been financially inclined since I was a kid," said Ebert, who declined to disclose how much he makes from Dinkytown.net. "I like to keep the focus on one thing and do that one thing really well."
Over the past few years, he has reworked his calculators so they function smoothly on mobile devices. He estimates he builds a new financial tool about every other month for clients. All of his calculators are available for free at Dinkytown.net and he personally answers user feedback by email.
His most popular calculator is one that automatically generates an estimated amortization schedule for a mortgage.
"What our members like about the calculator is that it helps them quickly figure out how much house they can afford, which is essential when you take out a mortgage," said Michael Toner, who manages digital channels for Navy Federal. "Online calculators are valuable to our efforts to improve financial literacy among our members and one of the most popular parts of our website and mobile app."
Ebert's favorite tool is the retirement planner because it gives one a solid estimate and only requires users to enter in eight numbers.
Not all of Ebert's creations are hits. His least-used tool determines the gain or loss if you have repossessed personal property from a deferred payment sale. "It is a great calculator, but it isn't popular due to its extremely specialized audience," he said.
Researchers from the Social Security Administration praised Ebert's work when they reviewed online tools that help people decide when to claim retirement benefits.
"Users can view the information in a variety of ways without leaving the calculator's single page. It is easy to use and navigate and offers a custom printable document with all the outputs," researchers found.
Striking the right balance between simplicity and accuracy is what separates good financial tools from the bad, said Stephen Wendel, head of behavioral science at investment research firm Morningstar.
"What is important is not the number itself, but how it is presented and whether it helps people take action," Wendel said. "The presentation is far more important than an extra decimal point of accuracy."
For Ebert, good financial tools answer one of these four fundamental financial questions:
"Everyone's issues may be different, but they all have these common threads," Ebert said. "The interesting part is even when the economy changes, the basic threads remain the same."
In the age of robo-advisors, Ebert said that online tools will not replace the human touch.
"Financial calculators can give users a good ballpark answer," he said. "When they want all the pieces lined up in the puzzle of financial planning, they should bring in a professional."