When it comes to saving and planning for retirement, you might be tempted to use different tools to see if you’re on the right track. In fact, all you have to do is search for the words “online retirement calculator” and you’ll get a whole host of free options to determine how far you are on track – or not.

At first glance, these online retirement calculators may seem very useful. But here’s why I’m really not a fan.

1. They make assumptions about your investment mix

Almost every online retirement calculator I’ve used so far asks me what my retirement plan balance looks like and how much I regularly contribute to my account each month. But many calculators don’t inquire about my investment composition. And those who To do ask me how invested tend to narrow down these choices to conservative, moderate, and aggressive, when in reality there are many in-betweens.

If you have an IRA or 401(k) plan heavily invested in stocks, it can generate significantly more growth than a bond-laden retirement plan. Any online retirement calculator that doesn’t make at least this basic distinction isn’t worth using.

2. They make assumptions about your spending

Online retirement calculators usually ask you what your annual income looks like. Based on that and your savings rate, they can make predictions about your future income and tell you if it will be enough or not. But I have a big problem with that, especially because the amount of money you make each year is not necessarily the amount you spend.

Let’s say you make $300,000 a year but manage to live comfortably on half that amount. In retirement, you may be able to maintain a good lifestyle on a third of that amount. But because online retirement calculators don’t typically take into account actual expenses, they can mislead you into thinking you won’t have enough income down the line.

3. They often fail to consider external sources of income

Many online retirement calculators I’ve played with have asked me how much money I’ve accumulated in my retirement account, and some have asked me to estimate my social security benefits or have for me. But most of these calculators don’t ask about income beyond that point.

Many seniors choose to work part-time in retirement, and if you go this route, it could give your income a serious boost. Likewise, you may decide to start a small business in retirement or own a second home that generates rental income for you when you’re not using it. While some online retirement calculators take these factors into account, many don’t, meaning the information they spit out isn’t accurate.

Use online retirement calculators with caution

While online retirement calculators can be a useful starting point for planning your retirement years, it may be best to sit down with a financial advisor and have that person run different scenarios based on your situation. particular, including your spending habits, retirement goals and a unique combination of investments. Taking this approach could save you a world of stress, while giving you a more accurate picture of where you really are.