Include 401k, IRA, brokerage — anything invested for retirement.
Not sure? Use your annual expenses x 25. Example: $40,000/year x 25 = $1,000,000.
7% is a common estimate for a diversified index fund portfolio after inflation.
Coast FIRE Calculator: Quick Answer
This coast fire calculator tells you how much you need invested today for your portfolio to grow to your retirement goal without any more contributions. Enter your age, target retirement age, current invested savings, FIRE number, and expected annual return. The result shows your Coast FIRE number, your gap, and your projected portfolio value at retirement.
If your current investments are above the Coast FIRE number, you may be able to stop saving for retirement and let compound growth carry the account to your target. If your current investments are below it, the gap shows how much more you need before coasting is realistic.
Use this tool after you estimate your full retirement number with the FIRE Calculator. Then compare the long-term growth math with the Compounding Calculator and the DCA Calculator.
What the Calculator Tells You
The main output is your Coast FIRE number. That is the amount you need invested now so your portfolio can grow into your full FIRE number by your target retirement age. The calculator also shows your current progress, your dollar gap, and what your existing savings may become by retirement.
For example, if your FIRE number is $1,000,000 and you have 35 years until retirement, you do not need $1,000,000 today. At a 7% real return, you need about $93,700 today. That is the amount that can grow to $1,000,000 over 35 years without new deposits.
The calculator is best for directional planning. It helps answer: Am I already coasting? How much more do I need? How sensitive is my plan to return assumptions? What happens if I retire at 60 instead of 65?
How to Use the Result for Real Decisions
If you are above your Coast FIRE number: you may be able to reduce or stop retirement contributions. That does not mean you should immediately quit all saving. It means your future retirement goal may already be funded if your assumptions hold.
If you want to lower contributions: consider keeping enough contributions to capture an employer match, fill tax-advantaged accounts when useful, or build a larger safety margin. Coast FIRE gives you flexibility, but a margin protects you from lower returns, higher expenses, and life changes.
If you want to switch jobs: Coast FIRE can make a lower-paying job less risky. If the new job covers your current bills and benefits, your retirement portfolio can keep compounding in the background. Compare the tradeoff with the Standard Retirement path if you are deciding between a slower career and a traditional plan.
If you want to retire earlier: run the calculator again with an earlier retirement age. Earlier retirement gives your money fewer years to grow, so the Coast FIRE number rises quickly. If you want full early retirement, use the FIRE Calculator first because Coast FIRE usually assumes you keep working in some form until the target age.
If you are deciding between debt payoff and investing: Coast FIRE can clarify the opportunity cost of sending extra money to a mortgage instead of the market. Use the Mortgage vs Invest Calculator for that specific decision.
Assumptions to Check Before You Coast
Expected return: The default 7% is a common long-term real return estimate for a stock-heavy index portfolio. Try 5%, 6%, and 7% to see a conservative range. A small change in return can move your Coast FIRE number by tens of thousands of dollars.
Inflation: Keep your inputs consistent. If your FIRE number is in today’s dollars, use a real return after inflation. If you use a nominal return before inflation, your FIRE number should also be inflated into future dollars.
Retirement age: A later retirement age gives your money more time to compound and lowers the amount needed today. An earlier age does the opposite. Test several ages before making a career change.
Withdrawal rate: Many FIRE plans start with the 4% rule, which means annual expenses multiplied by 25. The original Trinity Study research looked at historical withdrawal rates over 30-year retirement periods. You can read a current overview from Investopedia’s 4% rule guide.
Expenses: Your FIRE number depends on future spending. Housing, health care, taxes, family changes, and location can all change the number. If your expenses are uncertain, run a lean case, base case, and high-spend case.
Coast FIRE Examples
Example 1: Early saver at age 30. A 30-year-old wants $1,000,000 by age 65 and expects a 7% real return. The Coast FIRE number is about $93,700. If they already have $150,000 invested, they may be able to coast while still reaching the target.
Example 2: Mid-career job change at age 40. A 40-year-old wants $1,200,000 by age 65 and expects a 6% real return. The Coast FIRE number is about $279,000. If they have $250,000 invested, they are close, but not fully there. A few more years of contributions could make a lower-stress job more practical.
Example 3: Earlier retirement at age 55. A 35-year-old wants $1,500,000 by age 55 and expects a 6% real return. The Coast FIRE number is about $468,000. Early retirement requires much more saved today because the portfolio has only 20 years to compound.
Where Coast FIRE Fits in Your Investing Plan
Coast FIRE works best with broad, low-cost, long-term investments. If you are comparing index fund options, read VTI vs VOO, SPY vs VOO, and how to invest in index funds. These choices matter because the return assumption in the calculator depends on what you actually own.
Risk also matters. A stock-heavy portfolio can grow faster, but it can also fall hard near retirement. If you are close to your target age, review sequence of returns risk before relying on a single growth projection.
Before You Change Your Savings Rate
A coast fire calculator is a planning tool, not a permission slip. The number is useful because it turns a big retirement goal into a simple question: do you already have enough invested for time and compound growth to do most of the work? Before you lower your savings rate, test the result with numbers that are a little less friendly than your base case.
Start by running the coast fire calculator with your normal target age, normal FIRE number, and expected return. Then run it again with a lower return, a higher retirement goal, and a later or earlier retirement age. If the answer still looks strong, that is a better sign than one perfect result. If the answer changes a lot, your plan may need more margin.
Also think about what you will do with the extra cash flow. Coast FIRE does not have to mean spending every dollar you used to save. You might keep capturing an employer match, build a larger emergency fund, pay down debt, save for a house, or move some money into a taxable brokerage account. The coast fire calculator helps you see the retirement side, but your full plan still includes taxes, insurance, family needs, and job stability.
A good rule is to treat your first result as a draft. Save the numbers from the coast fire calculator, review them every year, and update the inputs when your income, expenses, portfolio balance, or retirement goal changes. Coast FIRE is strongest when it gives you more choices without making your future self depend on one optimistic forecast.
Frequently Asked Questions
A coast fire calculator estimates how much you need invested today for compound growth to carry your portfolio to your retirement goal without more contributions.
You may be able to stop saving specifically for retirement, but it is smart to keep an emergency fund, capture any employer match, and leave room for higher expenses or weaker market returns.
If your FIRE number is in today’s dollars, use a real return after inflation. Many people test 5%, 6%, and 7% for a diversified long-term portfolio.
No. Coast FIRE means your retirement portfolio may be on track without more contributions. You still need income for current living costs unless you have reached full FIRE.
Higher retirement expenses raise your FIRE number, which also raises your Coast FIRE number. Lower expenses reduce both numbers.
The 4% rule is a common starting point for a 30-year retirement plan. Early retirees often use a lower withdrawal rate or a larger margin because their money may need to last longer.
Next Step
Run the calculator with your real numbers, then run it again with conservative assumptions. If both versions say you are at Coast FIRE, you may have room to lower contributions, choose a better job, or plan a slower path to full retirement. If the conservative version shows a gap, use that gap as your next savings target.