In a financial emergency, you don’t want to rely on shaking coins out of your piggy bank, but if you don’t have a financial safety net in place, that’s exactly what you could end up doing. A financial safety net – or emergency fund – is a cash reserve that you can readily access to cover expenses in the event you’re sick or injured, out of work or have a large, unexpected expense.

Financial professionals typically recommend that you have three to six months’ worth of your must-pay living expenses stashed away in your emergency fund – enough to cover rent/mortgage, food, medications, transportation, insurance and recurring bills. In general, the less steady your income – and the more people are depending on that income – the bigger your fund should be.

Building an emergency fund can be a challenge, especially if you live paycheck-to-paycheck or have a tendency to spend more on unnecessary items than you can afford. (See Saving vs. Paying Off Debt for tips on how to balance these two goals.) Fortunately, technology can make the whole process easier.

5 Emergency-Fund Apps

Here are five mobile and web-based apps that can help you build a financial safety net.

1. Acorns

  • Platform: Web, iOS, Android
  • Cost: Free

Acorns connects to a credit card or debit card and checking account and “rounds up” the virtual change on purchases to the next dollar to help you save and invest. Once round-ups reach $5, Acorns withdraws the money and invests it in a personalized portfolio. You can also set recurring investment amounts if you want to invest more or add a lump sum into your account. Acorns constructs five portfolios, each made up of six exchange-traded funds (ETFs); your portfolio is optimized based on your age, time horizon, goals, income and risk tolerance. Fees apply: $1/month for accounts under $5,000; 0.25% per year for accounts over $5,000. Students and anyone under age 24 invest for free, regardless of account size. See also Acorns: The Perfect Investing Tool for Millennials.

2. Digit

  • Platform: SMS-based (you interact via text)
  • Cost: Free

Digit analyzes your spending habits and moves a few dollars (usually $5 to $50) from your checking account to your FDIC-insured Digit savings account – if you can afford it. To use Digit, you have to link your checking account so it can analyze your income and spending and find small sums of money you can safely set aside. The company claims it won’t ever transfer more than you can afford and offers a no-overdraft guarantee: If it overdrafts your account, Digit will cover the fee. You can withdraw money from your Digit account any time – as often as you wish and without paying a fee – by texting “withdraw” to Digit.

3. Level Money

  • Platform: iOS, Android
  • Cost: Free

Level Money is an award-winning app that lets you track your cash flow by acting as a mobile money meter. At the beginning of each month, Level Money "fills up" with your estimated income and automatically subtracts your recurring bills, plus a savings rate, such as 5%. The remaining money is what you have to spend that month. The app connects to your credit card and banking accounts, and every transaction adjusts the money meter so you can see, in real-time, if you are on track – or overspending. See also Is Level Money the Perfect Budgeting Tool?

4. PlentyFi

  • Platform: iOS, Android
  • Cost: Free

PlentyFi is an automatic savings program. You tell PlentyFi what you’re saving for – whether it’s a new car, a vacation or something else – and decide how much to transfer to your destination account and how often. PlentyFi uses ACH processing to automatically transfer the funds. PlentyFi claims that its users put aside an average of $300 a month using the app. While the current version of the app is free, the company indicates it plans to release a new version with enhanced functionality and fee-based features in the future.

5. SmartDeposit

  • Platform: Web
  • Cost: Annual fees of 0.35% for $0-$10,000; 0.25% for $10,000-$100,000; 0.15% for $100,000 plus

Betterment’s SmartDeposit makes automatic transfers from your checking account to an investment account when you have extra cash sitting around (note: the app only works with Betterment brokerage accounts). SmartDeposit uses algorithms to determine how much to transfer each month based on your account balance, income and spending habits. Before making a transfer, Betterment sends an email giving you the option to skip it. You set specific limits, including the maximum amount you want to keep in your checking account at any given time, and the maximum amount you’ll allow Betterment to transfer to the investment account at any time. It takes four to five business days to transfer money back to your checking account, so this app requires you to plan ahead.

The Bottom Line

The most effective ways to build an emergency fund are to budget your savings as part of your regular household expenses and cut back on discretionary spending. These apps can help you get there. It can be surprising to see how much money you have left over at the end of the month if you make a habit of asking yourself before every purchase: Is this something I really need to buy today? If it’s your mortgage payment, the answer is, of course, yes. But if it’s an impulse buy at the shopping mall, or that expensive morning coffee, maybe you could do without.

For more on this topic, see Why An Emergency Fund Is Important and Building an Emergency Fund.

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