Retirement Planning: How 401(k)s, IRAs, and Social Security Fit Together

Retirement planning is figuring out how much income you will need when you stop working, and building the accounts and benefits to provide it. For most Americans that income comes from three sources, or pillars: Social Security, an employer plan such as a 401(k), and personal savings such as IRAs. The job of planning is to understand what each will give you, close the gap to the life you want, and decide how to turn a lifetime of saving into a steady paycheck.

When I started, in my late fifties, I found this genuinely confusing. I had paid into retirement plans for thirty years and still could not have told you what they were worth or when I could touch them. So here is the whole picture in plain English, checked by a CERTIFIED FINANCIAL PLANNER: how the accounts work, how much you are likely to need, when you can retire, and how the money turns into income. If you want the single most useful first step, it is to check your Social Security statement.

The three pillars of retirement income

Almost every US retirement income is built from three pillars:

• Social Security: the federal benefit, paid from as early as 62 and based on your lifetime earnings record. The average benefit is about $2,071 a month in 2026, and the maximum at full retirement age is about $4,152 a month.
• Employer plans: the plans you build through your job, mainly the 401(k) (or a 403(b), 457, or TSP), where your employer often matches part of what you put in.
• Personal savings: anything you set up yourself, mainly traditional and Roth IRAs, plus regular taxable brokerage savings.

Understanding which pillars you have, and what each is worth, is the foundation of a plan. See types of retirement accounts for how they differ, and the crucial traditional vs Roth tax choice that runs through all of them.

How much do I need to retire?

The honest answer is that it depends on the life you want, but you can put numbers on it. Two common rules of thumb:

• Replacement ratio: aim to replace about 70% to 80% of your pre-retirement income each year.
• The 25x rule: a rough target nest egg is about 25 times the amount you plan to withdraw each year, which lines up with the 4% rule.

Social Security covers part of that income, so the question is how big a gap your savings need to fill. As a progress check, a widely-cited guide suggests having about 1x your salary saved by 30, 3x by 40, 6x by 50, and 10x by 67. We work through turning a target income into a target number in how much do I need to retire.

When can I retire?

Several different ages matter, and people often mix them up.

• 59½: you can take money from a 401(k) or IRA without the 10% early-withdrawal penalty.
• 62: the earliest you can claim Social Security, at a permanently reduced amount.
• 65: you become eligible for Medicare.
• 67: full retirement age for Social Security (anyone born in 1960 or later); waiting until 70 grows the benefit further.

Retiring is not all or nothing. Many people move to phased retirement or keep working in retirement, and some aim for early retirement. For the full picture, see when can I retire, and for the single biggest timing decision, when to claim Social Security.

How accounts grow: contributions and tax breaks

A retirement account is really a pot of investments wrapped in generous tax rules. Two things make it grow:

• Contributions: what you and your employer put in. In 2026 you can contribute up to $24,500 to a 401(k) and $7,500 to an IRA, with catch-up contributions once you turn 50. Always grab the full employer match first.
• Tax treatment: traditional vs Roth decides whether you get the tax break now (traditional) or tax-free withdrawals later (Roth).

The money is then invested, often in low-cost index or target-date funds, so it can grow over the decades before you need it. We cover the caps in retirement contribution limits and why costs matter in retirement account fees.

A caution that applies throughout: these accounts are invested, so the value can lose money, and you may get back less than you put in.

Getting your accounts in order

Before you can plan, you need to know what you already have. This is the part I found most satisfying once I started:

• Check your Social Security statement to see what you are on track for. See your Social Security statement.
• Track down old 401(k)s from previous jobs. See finding lost retirement accounts.
• Decide whether to roll them over into an IRA or your current plan. See 401(k) rollovers.

If you are just getting started, how to start saving for retirement walks through the order of operations.

Turning savings into income

This is the part that surprised me most: saving is only half the job, and some of the biggest decisions come at the end, when you turn the accounts into income. The main pieces are:

• Withdrawals: keep the money invested and draw from it. Flexible, but the value can fall and the money can run out if you withdraw too fast.
• Annuities: swap part of the savings for a guaranteed income for life. Secure, but usually irreversible.
• Required minimum distributions: starting at 73, the IRS makes you withdraw a minimum each year from traditional accounts. See required minimum distributions.

Watch the tax: Social Security can be partly taxable, traditional withdrawals are taxed as income, and large withdrawals can raise your Medicare premiums, as we explain in taxes in retirement. For the income comparison, see annuity vs drawdown, and to avoid running out, making your money last.

The steps of a retirement plan

Pulling it together, retirement planning is really a sequence:

1. Picture the life you want and put a rough yearly income on it.
2. Add up what you already have: Social Security estimate, 401(k)s, IRAs, and other savings.
3. Find the gap between the two.
4. Close it by saving more, working a little longer, or adjusting your expectations.
5. Decide how to draw the income, and when to claim Social Security and enroll in Medicare, then review the plan as you go.

You do not have to do all of this alone. Free official tools at SSA.gov, Medicare.gov, and Investor.gov can help, and for bigger or irreversible decisions a fiduciary advisor can too, as we cover in choosing a financial advisor. To see what the journey actually feels like, read my first year of retirement.