Free, with no signup. Coast FIRE is the point where your existing investments, growing on their own with no further contributions, will reach your retirement target by your chosen age. Works for one person or a couple with separate accounts against a shared retirement year. New to FIRE?
Money that arrives in retirement and reduces what your portfolio has to cover. All default to zero — leave them alone if none apply. Income before your retirement year is ignored here; that's already reflected in your contributions above.
Windfall — an RSU vest, inheritance, home sale, or bonus. Expense — a college bill, new roof, or car. Milestone — a dated marker on the chart with no dollar effect. One-off amounts only; for money that arrives every year, use Retirement income above.
| Year | Your age | Spouse age | Pre-tax | Roth | Taxable | Total | Coast threshold |
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Coast FIRE number = your FIRE number discounted back to today at the real return. If your current invested balance is at or above it, you've hit Coast FIRE and could stop contributing. The amber threshold line rises to your full FIRE number at retirement; the year your projected balance crosses it is your Coast FIRE point.
Max out: checking a box replaces that account's dollar input with the IRS annual limit, growing each year. Base limits are the 2026 figures — 401(k) $24,500, Roth IRA $7,500 — indexed to your inflation rate and floored to the nearest $500 (the way the IRS actually rounds). With catch-up on, an extra $8,000 (401k) / $1,000 (IRA) is added at age 50+, and the $11,250 SECURE 2.0 super catch-up replaces the standard 401(k) catch-up at ages 60–63. Employer match is separate from the employee deferral limit, so it's unaffected. Maxing the Roth assumes you're eligible or use a backdoor Roth — the tool doesn't check MAGI phase-outs.
The three buckets: balances are tracked as pre-tax (401(k), 403(b), traditional IRA — taxable as ordinary income later), Roth (tax-free later), and taxable liquid — and the three always sum to your total. Accounts with the same tax treatment are combined, so a traditional IRA sits with your 401(k) and vested RSUs sit with your taxable stocks. Pre-tax and Roth grow at the single Retirement growth rate; taxable liquid is split into cash, stocks, and bonds, each compounding at its own rate. This is a composition view: it shows the tax character of your money over time but does not net out future taxes, so the FIRE number is treated as pre-tax purchasing power.
Retirement income (Social Security, pension, rental or other cash flow) reduces what the portfolio has to cover. Two rules matter. Timing: only income already flowing at your target retirement year lowers your FIRE and coast numbers — a pension that starts at 65 when you plan to retire at 55 doesn't shrink the target, because the portfolio has to bridge those ten years alone. Later-starting income still shows up in the drawdown, where it's applied year by year from the age you enter. Inflation: Social Security is indexed, so it holds its value in today's dollars. A pension without a COLA does not — its dollar amount freezes at the level it starts at, and the tool erodes its purchasing power from there, which over a 25-year retirement is a large effect. Tick has a COLA only if your plan actually grants one. Income dated before your retirement year is ignored, since pre-retirement earnings are already represented by your contributions.
Drawdown: past your actual retirement year, withdrawals come out pro-rata across all buckets — not in a tax-optimized order — and only cover spending your retirement income doesn't. If the money runs out before the projection ends, the tool flags it.
Other simplifications: non-maxed contributions and employer match grow each year with the salary-growth rate. The FIRE number uses the withdrawal-rate rule; for early retirements a rate below 4% is more conservative. Social Security is entered as one combined household figure timed to your age, so a spouse claiming in a different year isn't modeled, and the benefit isn't recalculated for the claiming age you choose — enter the estimate that matches it. Returns are steady rather than random, so sequence-of-returns risk isn't simulated — real markets are lumpier, and a bad first decade hurts more than the average suggests. Tax brackets, RMDs, ACA subsidy cliffs, and healthcare costs are not modeled. Not tax, legal, or investment advice.
New to any of this? What FI, FIRE, and Coast FIRE mean — plain English, two minutes.