Retiring doesn't mean you will spend less money.
In fact, people often underestimate how much their ideal retirement will cost, according to author Dan Ariely, a professor of behavioral economics at Duke University.
Being tied to an office all day can make it harder to spend money, Ariely said. In retirement, the new hobbies and activities you pick up to fill your leisure time often come with a price.
"If you're in retirement, every day is like the weekend. Every day is expensive. You want to do things. Very few people just want to go fishing and walking in the woods," Ariely told CNBC.
The best-selling author conducted a study that found most people expected they would need to replace about 75% of their salary to fund their retirement.
Researchers then calculated how much the respondents would need based on their planned lifestyle. Ariely said the numbers were way off.
Watch this video to learn what percentage the same people actually would need and how to start saving more for retirement.
More from Invest in You:
This entrepreneur started a successful start-up by putting employees first
Want to give your finances a spring cleaning? First, get organized
Here's how you can save $500,000 for retirement on $35,000
SIGN UP: Money 101 is an 8-week learning course to financial freedom, delivered weekly to your inbox. For the Spanish version, Dinero 101, click here.
CHECK OUT: 27-year-old who turned $500 into $60,000: How to invest if 'you’re scared of losing money' with Acorns+CNBC
Disclosure: NBCUniversal and Comcast Ventures are investors in Acorns.