How Much to Save for Retirement: 6-Step Do-It-Yourself Math

Michael Chen

Michael Chen writes about personal finance fundamentals. Bay Area-based · finance enthusiast for 15 years.

Visual representation of the voice · not a photographic portrait

Quick answer: Estimate your yearly retirement spending, subtract expected Social Security and pension income, and multiply the gap by 25 to get a rough savings target. Then subtract what you already have and use a calculator to find the monthly amount. It is an estimate, so review it every year.↗ Share on X

You can estimate how much you need to save for retirement in six steps: figure out your yearly spending in retirement, subtract the income you expect from Social Security or a pension, find the yearly gap, multiply the gap by 25, account for inflation, and then work out the monthly amount needed to get there. The "multiply by 25" step comes from a well-known rule of thumb that says withdrawing about 4% of your savings in the first year, then adjusting for inflation, has historically lasted around 30 years. It is a starting estimate, not a promise, but it turns a scary question into a number you can work with.

This article walks you through each step with a worked example and a simple worksheet. It is educational information, not personal financial advice. For decisions about taxes, specific investments or a complicated situation, talk to a fee-only financial planner or a tax professional.

Step 1: How much will you spend each year in retirement?

READ ALSOHow to Read a Brokerage Statement: The 4 Parts That Matter →How to Calculate Retirement Savings Before Quitting →Retirement Income From Index Funds: The 3-Step Math →

Everything starts here. There are two common ways to estimate it.

Method A: The percentage shortcut. Many planners use 70% to 80% of your current pre-tax income as a first guess. The idea is that some costs drop when you stop working: commuting, work clothes, and saving for retirement itself.

Method B: The real budget (more accurate). Write down what you spend today and adjust each line:

In this example, retirement spending is $3,000 a month, or $36,000 a year in today's dollars.

Do not forget health care. Before Medicare starts at 65, you may need to buy your own coverage, and Medicare itself has premiums, deductibles and costs it does not cover.

Step 2: How much income will you get without touching savings?

Next, list the money that will arrive every month on its own:

• Social Security. Create a free "my Social Security" account at ssa.gov to see your personal estimate at different claiming ages. Do not guess this number. It depends on your work history and the age you claim.
• Pension. If your employer offers one, ask HR for your projected monthly benefit.
• Other steady income. Rental income, part-time work you realistically plan to do, or an annuity.

Continue the example: the estimate at ssa.gov shows $1,800 a month at full retirement age. No pension. That is $21,600 a year.

Step 3: What is your yearly income gap?

READ ALSOIndex Fund Myths: 8 Beliefs That Cost Beginners Money →13 Index Fund Mistakes Beginners Make (and Easy Fixes) →Rebalancing Index Funds: How to Cut the Capital Gains Tax →

Subtract Step 2 from Step 1.

$36,000 (spending) − $21,600 (Social Security) = $14,400 per year

This gap is what your savings must cover each year.

Step 4: How big does your nest egg need to be?

Multiply the yearly gap by 25.

$14,400 × 25 = $360,000

Why 25? It is the flip side of the 4% guideline. If you take 4% of $360,000 in the first year, you get $14,400. The guideline comes from studies of past U.S. stock and bond returns, and it assumes a retirement of roughly 30 years.

Some people choose a more careful multiplier:

The future can be worse than the past. A higher multiplier means saving more, but it gives you more room if markets do poorly early in retirement.

Step 5: What about inflation?

The numbers above are in today's dollars. Prices rise over time, so $360,000 will buy less in 25 years than it does now.

You have two simple choices:

1. Keep everything in today's dollars and use a "real" (after-inflation) return when you calculate savings in Step 6. This is the easier method for most people.

2. Convert to future dollars by growing the target by an assumed inflation rate each year. This gives a bigger, scarier number, but it is the same goal.

We will use option 1. A cautious assumption many planners use for a diversified portfolio is a real return in the range of 4% to 5% per year over long periods. Actual returns will be different, and some years will be negative.

Step 6: How much should you save each month?

Now subtract what you already have, then figure out the monthly amount.

Continue the example:

• Age today: 40
• Planned retirement age: 67 (27 years away)
• Already saved: $50,000
• Assumed real return: 4% per year

First, grow what you already have. $50,000 growing at 4% for 27 years becomes about $144,000 (in today's dollars).

Then, find the remaining gap. $360,000 − $144,000 = $216,000.

Finally, find the monthly savings. To build $216,000 in 27 years at 4% a year, you need to save roughly $370 a month.

You do not need to do this math by hand. Any free compound interest or "future value" calculator will do it. Type in the starting balance, the monthly contribution, the years and the return, and adjust the monthly amount until the result matches your target.

A worksheet you can fill in tonight

Copy these lines onto paper or into a spreadsheet:

1. Yearly retirement spending (today's dollars): $______

2. Yearly Social Security + pension + other steady income: $______

3. Yearly gap (line 1 − line 2): $______

4. Nest egg target (line 3 × 25, or × 28 to 30 for extra caution): $______

5. Current retirement savings: $______

6. Years until retirement: ______

7. Line 5 grown at your assumed real return for line 6 years: $______

8. Remaining gap (line 4 − line 7): $______

9. Monthly savings needed to reach line 8 (use a calculator): $______

What if the monthly number is too high?

Seeing a big number can feel discouraging. You have several levers, and small moves add up:

• Work a little longer. Each extra year means one more year of saving, one less year of withdrawals, and often a bigger Social Security check if you delay claiming.
• Capture the full employer match. If your 401(k) offers a match, contribute at least enough to get all of it. It is part of your pay.
• Raise your savings by 1% each year, ideally when you get a raise, so you do not feel the cut.
• Lower retirement spending. Paying off the mortgage before retiring or moving to a cheaper area can shrink line 1 a lot.
• Plan some part-time income in the early retirement years, if your health and job allow it.

Common mistakes that throw off the estimate

1. Using an expected return that is too high. Plugging in 10% a year makes the monthly number look tiny. Be conservative.

2. Forgetting taxes. Withdrawals from a traditional 401(k) or IRA are usually taxed as income. Your spending number should include the taxes you will pay.

3. Ignoring health care costs, especially between leaving work and age 65.

4. Guessing Social Security instead of checking your real estimate at ssa.gov.

5. Doing the math once and never again. Life changes. Redo this every year or after a big event like marriage, divorce, a new job or a health issue.

When should you talk to a professional?

This method works well for a basic estimate. Get help from a fee-only fiduciary financial planner (someone legally required to act in your interest and paid by you, not by commissions) if:

• You are within about 10 years of retiring.
• You have a pension with several payout options.
• You own a business, rental property, or have large stock options.
• You are deciding when to claim Social Security as a married couple.
• You have debt and are unsure whether to pay it off or invest.

Your next step

Tonight, log in or create your account at ssa.gov and write down your estimated Social Security benefit. Then fill in lines 1 to 4 of the worksheet above. Having your own target number, even a rough one, is the most useful thing you can do for your retirement this week.

FAQ

What is the 4% rule for retirement?

It is a rule of thumb based on past U.S. market returns: withdraw about 4% of your savings in the first year of retirement, then adjust for inflation. It suggests a target of about 25 times your yearly income gap. It is a guideline, not a promise.

Where can I find my Social Security estimate?

Create a free my Social Security account at ssa.gov. It shows your estimated benefit at different claiming ages based on your real work history.

Should I use a financial advisor for retirement planning?

A basic estimate is something you can do yourself. Consider a fee-only fiduciary planner if you are close to retiring, have a pension with several options, own a business or have a complex tax situation.

Educational content, not personalized financial advice. Sources cited where applicable.