Coast FIRE Calc

Free calculator for planning a sustainable early retirement

Coast FIRE Calc is a free web-based calculator built around the Coast FIRE philosophy of early retirement. The site offers a calculator plus educational guides on budgeting, expense tracking, net worth growth, and retirement planning. There is no price, no account required, and no paid tier. The tool's core function is to help you figure out if your current savings are enough to coast to your retirement goals through investment growth alone, without adding more money yourself.

The calculator differs from traditional FIRE planning, which the site frames as demanding that you save 50-70% of your income. Coast FIRE takes what the site calls "a more sustainable approach." The idea is simple: you front-load your retirement savings early in your career, reach a "coast number" (the amount that will grow to your target by your desired retirement age), and then stop contributing. From that point forward, compound interest handles the growth. The site presents this as a path to early retirement without extreme savings requirements, letting you make career decisions based on fulfillment rather than maximum earnings once you hit your coast number.

How money comes in

Coast FIRE Calc does not connect to any bank or brokerage. The calculator is a projection tool; you enter your own numbers. The site does not describe integration with Plaid, automated imports, or direct bank feeds. Money "comes in" to your simulation only through the values you type: your current age, your desired retirement age, your annual spending in retirement, how much you already have invested, how much you plan to contribute monthly, and what investment return rate you expect going forward.

The calculator default settings assume a 10% annual investment growth rate, which the site notes reflects "stock market average" returns before inflation. However, the site recommends using a more conservative 5-7% after-inflation return for your actual planning, "to build in a safety margin" since "past performance doesn't guarantee future returns." You also input an expected inflation rate (defaulting to 3% based on historical average) and choose a safe withdrawal rate (typically 4% based on the Trinity Study). The site mentions no other income sources (Social Security, pensions) in the calculator description, focusing instead on the core logic: how much your current and near-future savings will grow to by your target retirement age.

How the Coast FIRE planning workflow works

Coast FIRE Calc operates through a single, focused calculation: given your current savings, monthly contributions, expected returns, and target retirement age, will your portfolio be large enough that you can stop contributing and coast to your financial independence number? The site breaks this into steps. You enter your current age and planned retirement age. You specify your annual spending in retirement (the site says "typical US retirement age is 61," though you set your own target). You add your current invested assets, which the calculator specifies should exclude your primary home. Then you input how much you plan to contribute monthly, your expected investment growth rate, inflation expectations, fees, and your safe withdrawal rate. Clicking Calculate reveals whether you have reached your Coast FIRE number (shown in green) or not (shown in red), along with your projected retirement savings and expected annual retirement income plus a visual graph showing your coast path.

The site emphasizes the power of compound interest and timing. A concrete example: "a 30-year-old who has saved $200,000 might already have enough to coast to $1 million by age 65, assuming average market returns." The site argues that the earlier you invest, the more time your money has to grow; gains in later years are substantially larger than in early years because growth compounds exponentially, not linearly. The calculator is designed to make this clear and to show you exactly when you can stop contributing.

The site also discusses what to do if market performance disappoints. If you experience significant losses after reaching your Coast number, options include temporarily resuming contributions, adjusting your target retirement age, reducing planned spending, or increasing current income. The site frames market downturns as a normal part of investing and argues for maintaining flexibility in your plan rather than abandoning the strategy.

What it costs and what remains unanswered

Coast FIRE Calc is free. The site offers no pricing page and no mention of payment. There is no free trial converting to paid; the calculator is simply free to use. You do not enter an email to access it, and the site does not appear to monetize through ads or affiliate links in the calculator itself (though the broader site includes educational guides).

What the site does not clarify: it does not spell out whether the calculator accounts for taxes on investment gains or distributions in retirement. It does not explain how it handles Social Security, if at all. The default safe withdrawal rate is 4%, but the site does not detail what that means or how it relates to your actual expenses. The site acknowledges that "future performance isn't guaranteed" and that "life circumstances can change dramatically over decades," but it does not offer scenario testing or sensitivity analysis to show how changes in your assumptions affect the result. You can change inputs and recalculate, but the tool appears to give you one result: a yes-or-no answer and some projections, not a range of outcomes or probabilities.

Who it suits and who it does not

Coast FIRE Calc appeals to high earners in their 20s and 30s who want to front-load retirement savings and then shift to a less financially demanding career or lifestyle. The site presents Coast FIRE as particularly attractive for people who report "experiencing lower stress levels regarding their finances" once they reach their coast number, enabling them to "make career choices based on passion and fulfillment rather than purely financial considerations." Some Coast FIRE practitioners, the site notes, "switch to part-time work, while others pursue entrepreneurial ventures or transition to lower-paying but more meaningful careers."

The tool is less suited to people who want real-time expense tracking or who need to connect their bank accounts to monitor actual spending. It offers no budgeting features; it is pure projection. It is also not ideal for anyone who cannot front-load retirement savings early in their career, because the mathematics of compound interest require decades of growth. The site acknowledges: "While Coast FIRE is easier to achieve when you start young (due to having more time for compound interest to work), it's still possible to pursue if you're starting later." However, starting late requires either higher savings rates or pushing back your retirement age expectations. Additionally, if your life circumstances change, marriage, children, health issues, relocation to a higher-cost area, you will need to recalculate manually; the site does not track changes over time or update your coast number as life evolves.