For many, having $1 million saved for retirement sounds like plenty, but when you break down the numbers, what once seemed like a fortune might seem like just passable or maybe even too little to maintain the lifestyle you have or fund the one you want.

Obviously, there’s no single answer for whether $1 million is enough to keep someone afloat during retirement—ostensibly, a frequent first-class jetsetter is going to need much more than that while someone opting for only simple pleasures may be satisfied with less.

If you’re a baby boomer and come out shy of the million dollar mark, know that you’re very much not alone. According to a survey from GoBankingRates, only 22% of individuals ages 55-64 and older have $300,000 or more set aside for the future and about 29% of those over 65 have nothing saved at all.

In fact, most Americans (81%) don’t actually know how much they’ll need to retire. But thanks to some general guidelines and user-friendly retirement calculators, it’s easy enough to estimate your target savings and see whether $1 million will allow you to afford the post-work life of your dreams. But how?

One rule of thumb is to plan on replacing 70-90% of your current income with savings and social security once you leave the workforce. That means if you make the American median annual household income of $55,775, then you should anticipate needing $39,042.50-$50,197.50 per year during retirement. However in an article for AARP, Dan Yu of EisnerAmper Wealth Advisors said that for the first 10 years of retirement, you are more likely to be spending 100% of your current income.

Another way of looking at it is by first calculating the bare minimum of how much you’ll need per year and then working backwards to see how much you need to save. Investopedia recommends using the 4% sustainable withdrawal rate, what they describe as “the amount you can withdraw through thick and thin and still expect your portfolio to last at least 30 years,” as a means of calculation. That means if you have $1 million saved, then your yearly budget will be around $40,000. If your retirement aspirations lean more towards golf resorts than improving your home garden, even with the additional $16,000 or so per year that you’ll receive through social security, $1 million will clearly not sustain you for long.

There’s also the added variable of your expected lifespan. While it may seem bleak to confront your own mortality, you need to calculate your yearly saving and spending with a time frame in mind. According to the CDC, the average life expectancy in the United States back in 2014 was 78.8 years old. But given that more Americans are living past 90, and a 65 year old upper middle class couple has a 43% chance that one or both partners will live a full 30 years more, you may end up stretching your savings for longer than you could have ever imagined.

Where you plan on living also has a massive impact on how far $1 million will get you. While a retiree in Sherman, Texas could lead a nice cushy life for 30 work-free years with a retirement account of just $408,116, a retiree in New York City would need more than 5 times that. SmartAsset calculated that the average retiree in NYC needs $2,250,845 in savings, allocating $47,000 per year for housing alone. Even a nest egg in Brooklyn isn’t much better—that too requires more than $1 million. Perhaps for that reason, New York City isn’t on Forbes list of best places to retire in 2017.

Even with the most careful planning, there are always going to be a few financial surprises along the way that may set you back more than a few pennies worth. Whether they’re negative like medical emergencies and subsequent health expenses or positive, like travel fare to a destination wedding, they’re still taking a bite out of your bank account that may not have been in your original budget. For this reason, it’s important to use the above guidelines and calculation tools as a rough estimate, and be on the safe side by saving more than you think you’ll need.