Coast FIRE Calculator

Coast FIRE is the point at which your invested portfolio is large enough that — without adding another dollar — compound growth alone will carry it to your full FIRE number by your target retirement age. Once you hit your Coast FIRE number, you can stop saving for retirement entirely. You still need to earn enough to cover your current living expenses, but the future is funded.

The name captures the feeling: you've done the hard climbing, and now you can coast downhill to financial independence. Practically, Coast FIRE unlocks a menu of options that full FIRE doesn't offer until much later: shifting to less stressful work, going part-time, changing careers for meaning rather than income, or taking extended travel without worrying that you're falling behind on retirement savings.

The concept is part of the broader FIRE (Financial Independence, Retire Early) movement, which uses aggressive saving and index-fund investing to retire decades ahead of the traditional timeline. Unlike full FIRE — which requires accumulating 25× your annual spending before you can stop working — Coast FIRE is achievable with a much smaller portfolio, because time and compounding do the heavy lifting.

According to the SEC's Investor.gov compound interest calculator, even small differences in starting age dramatically affect how much you need to save. A 28-year-old targeting a $1.25 million retirement nest egg at 65 with a 7% real return needs a Coast FIRE number of roughly $102,000 — an amount many people can reach in their early 30s with consistent saving. A 40-year-old targeting the same goal needs about $230,000. Waiting from 28 to 40 adds about $128,000 in required savings.

This calculator shows you three critical numbers: your full FIRE number (what you ultimately need), your Coast FIRE number (what you need invested today to coast from here), and how many years earlier Coast FIRE arrives versus grinding to full FIRE without stopping contributions. The chart visualizes both curves — your actual portfolio growth and the required "coast number" at each age — so you can see exactly when they intersect.

The Coast FIRE calculation uses two formulas in sequence. First, calculate your full FIRE number using the safe withdrawal rate (SWR). Then discount that target back to present value using the compound growth formula.

Step 1: Your Full FIRE Number

The 4% SWR comes from the Trinity Study (Cooley, Hubbard, Walz — 1998, updated 2011), which found that a 4% initial withdrawal rate, adjusted for inflation annually, sustained a diversified portfolio through 95%+ of historical 30-year periods. For longer retirements (40+ years), many planners use 3.5%.

Step 2: Your Coast FIRE Number (Present Value)

This is the standard present value formula from finance — the same math used to value bonds and pension obligations. It answers: "How much money, invested today at the expected return, grows to the target by retirement?" The Federal Reserve uses analogous discounting in its monetary policy models.

What Real Return Rate Should You Use?

The calculator defaults to 7% as an example real return; test a lower rate too. This is already net of inflation — meaning all dollar figures stay in today's purchasing power without needing a separate inflation adjustment.

All figures are approximate, rounded to nearest $1,000. Formula: $1,250,000 ÷ (1.07)^n where n = years to retirement. Adjust your return assumption for conservative portfolios.

Enter your numbers and the calculator updates instantly — no button click needed. Here's what each input means and how to choose the right values:

The calculator returns four outputs and an interactive chart. Here's how to read each:

• FIRE Number Your full retirement target — the portfolio needed to live off investment returns indefinitely. This is the destination; Coast FIRE is a milestone you can hit en route.
• Coast FIRE Number The highlighted output. If your current portfolio already exceeds this number, you have already hit Coast FIRE — the compounding math will carry you to your FIRE number without another contribution.
• Status "Already Coasting!" means stop worrying about retirement savings — cover your living expenses and let compound interest do the rest. A number of years means you're on track and that's when you'll cross the line. A dollar gap is what you still need to invest to reach coast.
• Years Saved vs Full FIRE How many years earlier you can stop mandatory retirement saving (Coast FIRE) compared to fully accumulating your FIRE number.

Reading the chart: The "Your Portfolio" curve shows your actual portfolio growing with contributions, then continuing to grow (more slowly) without them after you coast. The "Coast Target" curve shows the required coast number at each age — it rises over time because as you get older, compound interest has fewer years to work, so you need more saved right now. Where the portfolio curve crosses the coast target: that's your Coast FIRE date.

Reaching Coast FIRE is a genuine inflection point, not just a milestone. Here's what it actually unlocks:

• Take a lower-paying job you actually want. A journalist, teacher, nonprofit worker, or tradesperson earning $45,000/year who has coasted their retirement savings has the same financial security as a stressed-out lawyer earning $200,000 who hasn't. The income requirement drops from "cover expenses and save aggressively" to "cover expenses only."
• Go part-time or freelance. If your Coast FIRE number also covers your monthly bills at reduced hours, you've effectively reached what the FIRE community calls Barista FIRE simultaneously. The Barista FIRE Calculator models this hybrid path specifically.
• Take a sabbatical or travel year. A 6–12 month gap year costs you nothing in retirement readiness — you're coasting. The only requirement is covering living expenses during the break.
• Keep contributing if you want to reach full FIRE earlier. Coast FIRE is a floor, not a ceiling. Every dollar you continue to invest after coasting accelerates your full FIRE date. Use the FIRE Calculator to model different contribution scenarios from your current position.
• Validate your SWR assumption. A 4% withdrawal rate lasted 30 years in most historical periods tested. For 40+ years, revisit with the Safe Withdrawal Rate Calculator — many early retirees target 3.5% for an extra margin of safety.

One critical caveat: Coast FIRE assumes your portfolio continues growing at the expected real return without withdrawals. A prolonged bear market early in your coasting phase can meaningfully extend your full FIRE timeline — the same sequence-of-returns risk that affects early retirees. Building a 10–15% buffer above your calculated Coast FIRE number is the standard guidance to account for this volatility.