On average, the weekly amount that people spend — not including bills like mortgage or rent, utilities, etc. — is $340, or $143 more than the average $197 budgeted. That extra spending equals roughly $7,400 each year.

Even though most consumers (74%) say they have a budget, 79% of them fail to follow to it, according to research from crowdsourced shopping platform Slickdeals.net.

For most households, sticking to a budget is apparently far easier said than done.

Many people struggle with overspending regardless of how much they earn, according to certified financial planner Josh Nelson, founder and CEO of Keystone Financial Services in Loveland, Colorado.

"I've heard 'I don't know where all the money goes' from people who make a gazillion dollars and from poor college students and everyone in between," Nelson said.

The survey asked 2,000 adults about their budgeting habits and weekly spending. Topping the list of categories where respondents overspend is online shopping, followed by grocery shopping and subscription services. (And, yes, overindulging on coffee ranks in the top 10.)

While the survey didn't explore how people are funding those extras, credit cards could be a culprit. As of the third quarter, consumers were carrying nearly $1.1 trillion in such debt, up from $888 billion five years ago, according to the Federal Reserve. Separate data from CompareCards.com shows that just 38% of cardholders are "very confident" they can pay their monthly balance in full.

If going over your budget is causing credit card debt to pile up or is standing in the way of your ability to reach other goals, there are some ways to rein yourself in, financial advisors say.

TOP 10 WEEKLY BUDGET BUSTERS Online shopping: 40%

Grocery shopping: 39%

Subscription services: 37%

Technology products: 36%

Buying lunch everyday: 35%

Household essentials: 32%

Coffee: 32%

Food delivery: 32%

Gym memberships: 30%

Entertainment (movies, concerts, etc.): 29% Source: SlickDeals.net

For starters, make sure your budget is realistic.

"Most people hate budgeting and going through the exercise of figuring out where they're spending their money," Nelson said. "But people end up finding a lot of areas where they can cut back without affecting their quality of life one bit."

For example, he said, you might be paying subscriptions for online publications, games and services that you no longer need.

"Sometimes people don't even know they're still being charged for things they aren't using," Nelson said.