In the last post, we talked about how everyone loves a good rule of thumb. Save 15% of your income. Follow the 50/30/20 rule. Put away 10% and you'll be fine.
Simple. Clean. Universally applicable.
And completely useless for planning your retirement.
The truth is that what you need to save depends entirely on your circumstances—when you start, when you want to stop working, how long you'll live, and critically, how much you earn and what Social Security will actually replace. The difference between starting at 25 versus 45 isn't a small adjustment. It's the difference between saving 11.5% of your income and saving 31.5%. And if you're a high earner? The numbers look even more stark.
Let me show you exactly what I mean with real numbers—and explain why Social Security makes everything more complicated than those generic savings calculators would have you believe.
Understanding Social Security First
Before we dive into the savings numbers, you need to understand something important: Social Security doesn't replace the same percentage of income for everyone. And unless you understand this, you can't build an accurate retirement plan.
If you look at the general population, virtually everybody understands what Social Security retirement income is. A smaller portion of the population maybe understands how it's funded via payroll taxes. And then a very, very small portion of the population understands how your Social Security benefit is calculated.
Here's the thing: knowing how your benefit is calculated can go a long way toward helping you understand how much you need to save. So let me walk you through six real couples and show you exactly how their income levels dictated their Social Security benefits—and therefore how much they had to save.
Six Couples, Six Different Realities
I'm going to show you six sample couples. They all start at 35 with nothing saved. They'll all retire at 65 and need to plan for a 30-year retirement. They all want to live on 75% of their pre-retirement income.
The only differences? Their income levels—and how that income is distributed between spouses.
I'm looking at couples making $40,000, $80,000, and $240,000. And for each income level, I'm comparing two scenarios: one where there's a single breadwinner, and one where both spouses earn equally.
Even though household income is identical in each pair, the way that income is earned between spouses dramatically impacts the Social Security benefit. And I'll explain why.
Couple 1 & 2: $40,000 Household Income
Couple 1 (Single Breadwinner: $40,000 / $0)
- Needs to save: 6.5% of income
- Full retirement age Social Security benefit: ~$30,000/year
- Social Security replacement rate: 76% of pre-retirement income
- Probability of success: Nearly 100%
Couple 2 (Equal Earners: $20,000 / $20,000)
- Needs to save: 6.5% of income
- Full retirement age Social Security benefit: ~$27,700/year
- Social Security replacement rate: 69% of pre-retirement income
- Probability of success: Only 84%
Notice what happened? Same household income. Different distribution between spouses. The single-breadwinner couple gets $2,300 more per year from Social Security and replaces 7% more of their pre-retirement income. That's meaningful.
Couple 3 & 4: $80,000 Household Income
Couple 3 (Single Breadwinner: $80,000 / $0)
- Needs to save: 16% of income
- Full retirement age Social Security benefit: ~$49,000/year
- Social Security replacement rate: 61% of pre-retirement income
- Probability of success: Nearly 100%
Couple 4 (Equal Earners: $40,000 / $40,000)
- Needs to save: 16% of income
- Full retirement age Social Security benefit: ~$40,000/year
- Social Security replacement rate: 50% of pre-retirement income
- Probability of success: Only 90%
Again, same household income. But the single-breadwinner couple gets $9,000 more per year from Social Security—an 11% higher replacement rate. Starting to see the pattern?
Couple 5 & 6: $240,000 Household Income
This is where things get really interesting—and the pattern breaks.
Couple 5 (Single Breadwinner: $240,000 / $0)
- Needs to save: 40% of income
- Full retirement age Social Security benefit: ~$66,000/year
- Social Security replacement rate: Only 28% of pre-retirement income
- Probability of success: Nearly 100%
Couple 6 (Equal Earners: $120,000 / $120,000)
- Needs to save: 35% of income
- Full retirement age Social Security benefit: ~$77,000/year
- Social Security replacement rate: 32% of pre-retirement income
- Probability of success: Nearly 100%
Wait—what? Now the equal-earner couple gets MORE from Social Security and needs to save LESS than the single-breadwinner couple.
What happened?
The Social Security Wage Base: Where Everything Changes
Here's what most people don't understand: Social Security has a maximum taxable wage base. In 2025, it was $176,100. Once you earn more than that, you stop paying Social Security taxes—but you also stop getting credit toward your benefit.
So, in Couple 5, where one spouse earns $240,000, only the first $160,200 counts toward their Social Security benefit. That's about 67% of their actual earnings. The other $79,800? Doesn't count at all.
But in Couple 6, where each spouse earns $120,000, BOTH are under the wage base. So, 100% of their earnings count toward their benefits. They're each getting full credit, which is why their combined household benefit is higher—even though their household income is identical.
This is one of the most misunderstood aspects of Social Security planning. And it dramatically affects how much high earners need to save.
How Social Security Benefits Are Actually Calculated
Let me show you the formula that creates this progressive structure. It's straightforward once you see it.
Social Security takes your highest 35 years of earnings, indexes them for inflation, divides by 420 months, and gets your Average Indexed Monthly Earnings (AIME).
Then they apply this formula:
- 90% of the first $1,115 of AIME
- 32% of AIME between $1,115 and $6,721
- 15% of AIME above $6,721
See the pattern? You get significantly more credit for your first dollars of earnings than your last. The higher your income, the smaller the percentage that gets replaced.
This is intentional. Social Security is designed to be a progressive system—it replaces a higher percentage of income for lower earners and a lower percentage for higher earners.
Real Data from the Social Security Administration
According to Social Security Administration research on beneficiaries, here's what Social Security replaces based on lifetime earnings by income quintile:
- Lowest earners: 224% (often reflects spousal benefits for those with little to no lifetime earnings)
- Second quintile: 66%
- Middle earners: 47%
- Fourth quintile: 39%
- Highest earners: 34%
Read that again. If you're in the highest earning quintile, Social Security replaces only 34% of your wage-indexed lifetime earnings (probably less if you're at the very top). If you're in the middle, it's 47%. For the lowest earners, it can exceed 200%, but that's often because they're receiving spousal benefits despite having minimal personal earnings.
This matches exactly what we saw in our six couples. The $40,000 household had 76% replacement. The $240,000 household? Only 28%.
Back to Savings Requirements: Time Matters More Than You Think
Now that you understand how Social Security works, let me show you what happens when we factor in WHEN you start saving.
I ran projections for a hypothetical couple earning $120,000 who wants to retire on $96,000 (80% replacement). They'll get about $52,000 from Social Security at 65. I assumed 5.97% returns and ran Monte Carlo simulations (a simulator that attempts to show how many times you will fail to meet your goal given different return patterns – oversimplified) to get an 80% probability of success.
Here's what they'd need to save as a percentage of gross income, depending on when they start:
If you start at 25:
- Retire at 55, live to 83/85: Save 33.5%
- Retire at 55, live to 95: Save 37.0%
- Retire at 65, live to 83/85: Save 11.5%
- Retire at 65, live to 95: Save 14.5%
If you start at 35:
- Retire at 55, live to 83/85: Save 60.0%
- Retire at 55, live to 95: Save 65.0%
- Retire at 65, live to 83/85: Save 18.0%
- Retire at 65, live to 95: Save 22.5%
If you start at 45:
- Retire at 55: Not mathematically feasible for most people
- Retire at 65, live to 83/85: Save 31.5%
- Retire at 65, live to 95: Save 39.5%
If you're 25 and want to retire at 65, saving 11.5% might get you there. If you're 35 and want the same thing, you need 18%. Wait until 45? You're looking at 31.5%—nearly triple.
And if you want to retire early? Starting at 35 and hoping to retire at 55 means saving 60-65% of your gross income. Good luck with that.
What This Means for Different Income Levels
For High Earners:
Remember those six couples? The high-earning couple at $240,000 only got 28-32% of their income replaced by Social Security. Those numbers I just showed you for a $120,000 couple? They're actually understated for you.
Let's say you're a couple earning $200,000 instead of $120,000, and you still want to retire on 80% of that income—$160,000. Social Security might give you around $60,000-$70,000 (the maximum benefit is capped). That's only 30-35% of your pre-retirement income.
You need to make up the other $90,000-$100,000 per year. Every year. For 30+ years.
The generic "save 15%" advice? It's not even close to enough. Depending on when you start, you might need to save 25%, 35%, or even 45% of your income to hit your retirement goals.
For Lower Earners:
If you're earning $60,000 as a couple and want to retire on $48,000, Social Security might replace 50-60% of that, leaving you to make up $20,000-$25,000 per year from savings. The percentage you need to save is lower than middle or high earners, but it's still substantial if you start late.
The problem is that lower earners often have less margin in their budgets to save aggressively. Starting early becomes even more critical when you can't afford to save 30-40% of your income in your 40s.
The Longevity Problem Applies to Everyone
Notice how the numbers jump when I assume you'll live to 95 instead of 83/85? That's 10-12 extra years of retirement you need to fund. For someone starting at 45 who wants to retire at 65, that difference means saving 39.5% instead of 31.5%—an extra $9,600 per year on a $120,000 income.
Medical advances mean more people are living into their 90s. And if you're a high earner with access to better healthcare, quality food, and less physically demanding work, you're even more likely to live longer.
Why Generic Advice Fails
This is why one-size-fits-all advice is worse than useless, it's dangerous. "Save 15% and you'll be fine" might work for:
- Someone who starts at 25
- Plans to work until 65
- Earns a middle-income salary
- Has average life expectancy
- Gets close to 50% income replacement from Social Security
But it completely falls apart if you're a high earner who started late, wants to retire early, is likely to live past 90, or—critically—will only get 30-35% income replacement from Social Security instead of 50%.
The math doesn't care about what sounds reasonable or what financial gurus say on podcasts. It just is what it is. And the math is different for a couple getting 76% replacement from Social Security versus one getting 28%.
So, What Do You Actually Need to Do?
First, understand your Social Security replacement rate. Don't assume it's 50%. If you're a high earner, it's closer to 30-35%. If you're a lower earner, it might be 60-70%. Use the Social Security Administration's online calculator to get an actual estimate based on your earnings history.
Second, stop pretending that what works for someone else will work for you. Run your own numbers based on:
- When you want to retire
- How long you might live (add at least 5 years to whatever you're thinking)
- What income you'll actually need
- What Social Security will realistically replace at YOUR income level
- How your household income is distributed between spouses
- How much you've already saved
- How much time you have left
Third, understand that time is your most valuable asset. Every year you wait makes the problem exponentially harder. The couple who starts at 25 and retires at 65 needs to save 11.5%. Wait until 45? Now it's 31.5%—and that's assuming you're a middle earner with a decent Social Security replacement rate. If you're high-income with only 30% replacement, it could be 40% or more.
Fourth, if you're a high earner, adjust your expectations. Social Security will replace less of your income than you think—probably 30-35% at most. You're going to need to save more than the middle-income examples you see in most financial planning articles. A lot more.
And if you're a lower earner, the good news is that Social Security replaces a higher percentage of your income—often 60% or more. The bad news is that you likely have less margin to save aggressively if you start late. Starting early isn't just important for you, it's essential.
The Point
Compound interest rewards people who start early and makes things harder for people who wait. Social Security's progressive benefit structure means high earners need to save more and low earners get more help, but neither group can rely on generic advice.
And most importantly: the specifics matter. How much you earn. How that income is distributed between spouses. The specific percentage Social Security will replace. When you start saving. When you want to retire. How long you'll live.
You can follow one-size-fits-all rules and hope it works out. Or you can look at your situation—your age, your income, your Social Security replacement rate, your goals, your timeline—and figure out what YOU need to do.
Stop waiting for someone to tell you a comfortable number that applies to everyone. Get educated. Know your numbers. Build your plan based on your specific circumstances.
Because while they say it's never too late, the math of financial planning tells a different story—and that story is different for everyone. Especially when it comes to Social Security.
A couple final notes: Couple 5&6 above need to save 35-40% of their income in that example to live on 75% of pre-retirement income. If they’re saving that much, they’re obviously living on less than 75% right now. Same as the late starting or early retiring couples – saving 30-65% means you’re not living on 80% right now, so it’s probably not going to be your goal, but understanding numbers prevents your retirement income from being an unintentional side effect of lack of savings. Can returns be higher than the 5-6% illustrated? Absolutely, and they often have been, but there’s no guarantee that that will be so, which is why we typically use more conservative numbers for planning. The post is meant to illustrate the point that time and income replacement rates are critical to know. How you choose to weight each is based on your own comfort level.
LPL Financial does not offer tax or legal advice.
This information is provided for educational purposes only and is believed to be accurate. The hypothetical examples presented are for illustrative purposes only and are not intended to represent any specific product. The information is intended to be generic in nature and should not be applied or relied upon in any particular situation without the advice of your tax, legal and/or financial services professional. It should not be considered investment advice, nor does it constitute a recommendation to take a particular course of action.