You'll have a hard time retiring without this, and it's not money

When most people talk about preparing for retirement, the focus is on money – how much they need, how much they can afford to save, where to put it, and so on. This is understandable. Retirement saving is the biggest financial goal most people will ever have, and it'll cost a lot of money.

But just throwing cash in a retirement account isn't going to cut it. If you truly want to retire comfortably, you'll need something else.

Don't guess at your retirement costs

If you're just saving a random amount of money each month, there's a chance you'll wind up with far less than you actually need. To avoid this, you need an accurate estimate of your retirement costs and then a clear plan for how to save that amount.

You can begin to estimate how much you need to save for retirement by asking yourself the following questions:

• When do I plan to retire?
• How long do I expect to live?
• Where do I want to live in retirement?
• How do I plan to spend my time in retirement?
• How much money do I expect to get from Social Security and other sources?

Once you know the answers to these questions, you can begin to figure out your retirement savings target. You might assume that you'll need less than your annual pre-retirement income in retirement, and this is the case for some people, but not all. If you plan to travel or make some expensive purchases, you might need as much or more than you're used to earning now.

Building your retirement roadmap

Once you've settled on a retirement savings target, you need to build a plan for how you'll save the money you need. Ideally, this plan involves monthly retirement contributions to a 401(k), an IRA, or some other account.

You'll need to invest your personal contributions, and that means you'll have investment earnings to help you cover your costs as well. But it's important not to overestimate your returns. It'd be great if we could all earn 20% on our investments year after year, but a return of about 6% is a safer assumption. This may be a little conservative; your investments could grow faster. But if not, you at least won't fall behind on your savings goals due to poor investment growth.

You can use a retirement calculator to estimate how much you need to save per month to achieve your goal. If you qualify for a 401(k) match, you may subtract a portion of this from your savings goal. For example, if your goal is to save $500 per month for retirement and you qualify for a $2,400 401(k) match, you could subtract 1/12 of this – $200 – from your monthly savings target, leaving you with $300 to save on your own each month.

As you go through this process, you might find that your initial retirement plan isn't feasible. This often happens if you cannot afford to save the required amount in the time you have left until your chosen retirement date. If you run into this issue, you'll have to make some tweaks. You might have to delay your retirement date or consider working part-time in retirement to reduce how much you need to save.

Play around with a few alternatives until you find a plan that's right for you. Then, do your best to stick to it. Check in with yourself at least once per year or whenever you experience a major life or financial change, and adapt your plan as needed to keep yourself on track.

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