Almost three-quarters of Americans plan to work past retirement age, according to a recent Gallup poll. And while most of those people expect to work only part-time when they are over 65, a bit more than 10% of us think we'll be working full-time well into our golden years.  

These numbers reflect a major shift that has taken place over the past two decades: Non-retirees in 1995 were significantly more likely to believe they'd be out of the workforce before their 65th birthday. Today's workers often plan to work longer because they want to, but there's a sizable fraction of Americans who think they'll have no choice because of their financial situations. 

If you want the flexibility of being able to decide when you'll retire, here are a few key rules to follow.

Calendar with time to retire written in red

Image source: Getty Images.

1. Set your target date ASAP 

If you decide at 55 that you want to retire at 56, chances are, unless you've being making plans all along, you won't be in a financial position to do so. But, if you decide when you're 25 that you want to retire early, and you act in accordance with that goal over the decades, you could very well achieve that dream

Once you decide on a retirement target date, you can structure your savings to meet that goal. While there may be bumps in the road, the younger you are when you start putting your retirement plan in place, the more time you'll have to recover from setbacks.

If you've already missed your chance to start saving at 25, well, you'll never be younger again than you are now. If you set a target retirement date today, you can consider what sacrifices you might choose to make to get you there -- for example, moving to a cheaper house so you can afford to channel more funds into maxing out your retirement account contributions. 

Attempting to set that target date could also reveal that you're being unrealistic. If you want to retire in 10 years and have $0 saved, doing the calculations on how much you'd need to put aside every month could serve as a wake-up call to adjust your expectations -- and as an impetus to start looking for ways to stay in the workforce longer.

Bottom line: No matter how old you are, if you haven't done so yet, now is the time to decide your ideal date for retirement and then to evaluate it against your financial resources.

2. Understand how retirement age will affect income

Whatever the number you target, your retirement age will have a big impact on your income for many reasons. 

  • The younger you are when you retire, the longer your savings will need to last, and the more conservative you'll need to be about how much you withdraw annually. You'll also have fewer years to work and invest, which means you'll need to invest much more aggressively.
  • The age you are when you apply for Social Security benefits directly affects how large your monthly checks will be. Also, retiring before you've worked for at least 35 years will significantly cut into those checks, because the formula the Social Security Administration uses is based on an inflation-adjusted average of your highest 35 years of wages. You don't want zeros going into that calculation. Applying before full retirement age also reduces your monthly check, while waiting boosts its size (though that maxes out at age 70). The chart in this article details precisely how retiring early or late could affect your Social Security benefits
  • If you retire before 65, which is when you become eligible for Medicare, you will need a plan for where you'll get healthcare coverage in the interim, and how you'll pay for it. 

You can't pick your perfect retirement age without taking all of these factors into account. There are benefits associated with waiting to retire, including the chance to boost your Social Security income, but you'll lose out on some happy, healthy years in retirement if you wait. Once you understand exactly how early or late retirement affects your income, you can do a more accurate assessment of the pros and cons of different retirement ages.

3. Don't retire without a plan for worst-case scenarios

Whatever your target retirement age is, you probably based it in part on your vision of a dream retirement. That picture looks different for everyone, but it's not much of a stretch to assume yours involves you (and your spouse or partner, if you have one) staying healthy, your kids (if any) being out of the house, and you having the time to travel or otherwise indulge your hobbies. 

While it's good to have a dream to pursue, its also important to ensure you have plans for what you'll do if things go wrong. If you're counting on both your own Social Security and your spouse's benefits in your budget plan, would you have enough money if your spouse passed away before retiring? If you're expecting to downsize, would you still be OK financially if your kids had to move back home and you couldn't? If you and your spouse both needed costly medical care, could you afford it?

You can't plan for every possible calamity -- but before you decide you're ready to retire, think through some of the problems that could arise and have a contingency plan in place. This could include investing in a health savings account before you retire to help cover expenses later, paying off your mortgage, working a little longer than anticipated, or making adjustments to your desired retirement age so you don't leave the workforce until you're really sure you're ready. 

What's your perfect retirement age?

There are lots of other factors you can consider when picking the perfect retirement age, including what exactly you want to do with your time during retirement.

Ultimately, though, financial security remains a top concern for retirees, and it should be the major point you consider. That's why you can't pick your perfect retirement age until you know when you'll have enough money for your needs, plus some to cushion you against the unexpected bumps in the road.

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