Coast FIRE Calculator USA

To use the Coast FIRE calculator for the USA, enter your age, your planned retirement age, the yearly spending your portfolio must cover, and the amount you have invested today. The calculator returns your Coast FIRE number: the balance your 401(k), IRA, and brokerage accounts need today to grow into a full retirement fund with no more contributions.

1. Enter your Current Age. Use your age today, in whole years.
2. Set your Retirement Age. Many Americans use 67, the Social Security full retirement age (FRA) for anyone born in 1960 or later. You can pick an earlier age, but 401(k) and traditional IRA withdrawals before age 59½ usually carry a 10% IRS penalty.
3. Enter Annual Spending in Retirement in today's dollars. Enter only the part your investments must pay for. Subtract the Social Security benefit you expect, which you can look up in your my Social Security account at ssa.gov.
4. Enter Current Invested Assets. Add your 401(k), 403(b), traditional IRA, Roth IRA, invested HSA balance, and taxable brokerage account. Leave out home equity and your emergency fund.
5. Enter your Monthly contribution. Count your own 401(k) deferrals, your employer match, and any IRA or brokerage deposits.
6. Check Advanced Settings. The defaults are a 7% investment growth rate, 3% inflation, and a 4% safe withdrawal rate (SWR). Adjust them to match your own assumptions.

How to read your results

• Coast FIRE number (the large figure) is the amount you need invested today. Hit it and you can stop saving for retirement.
• Progress shows your current invested assets as a percentage of your Coast FIRE number.
• FIRE Nest Egg is the full portfolio you need on your retirement date, in today's dollars.
• Coast Age is the age at which your balance, with your monthly contributions, reaches the Coast FIRE line.
• Cash Freed is your monthly contribution times 12: the yearly cash you get back once you coast.
• Real Return is your growth rate after inflation.
• Growth Projection charts two paths, coasting from today and saving until retirement, against your target nest egg.

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The Coast FIRE calculator works backward from your retirement goal. It finds the full nest egg your spending requires, then discounts that amount by the inflation-adjusted growth your portfolio can earn between now and retirement.

The formula

FIRE Nest Egg     = Annual Spending ÷ Safe Withdrawal Rate
Real Return (r)   = (1 + Growth Rate) ÷ (1 + Inflation Rate) − 1
Coast FIRE Number = FIRE Nest Egg ÷ (1 + r)^Years

Worked example

Maria is 32 and plans to retire at 65. She expects to spend $60,000 a year in retirement and estimates $24,000 a year from Social Security, so her portfolio must cover $36,000.

1. FIRE Nest Egg: $36,000 ÷ 0.04 = $900,000
2. Real Return: 1.07 ÷ 1.03 − 1 = 3.88%
3. Growth factor: 1.0388 raised to 33 years = 3.516
4. Coast FIRE number: $900,000 ÷ 3.516 = $255,980

Maria has $120,000 in her 401(k) and Roth IRA, so she is 47% of the way there. Left alone, $120,000 grows to about $421,908 by 65, well short of $900,000. With $800 a month in contributions, she reaches Coast FIRE at age 53, and from then on she can redirect $9,600 a year to anything she wants.

Factors that change your result

• Taxes. Traditional 401(k) and IRA withdrawals are taxed as income. Enter pre-tax spending if most of your money sits in traditional accounts.
• Fees. A fund charging 0.5% a year turns a 7% return into 6.5%. Lower the growth rate by your expense ratio.
• Social Security. Recent Trustees Reports project the trust funds can pay roughly 80% of scheduled benefits once reserves run out in the mid-2030s. Planning on a reduced benefit adds a safety margin.
• Constant returns. The calculator assumes the same return every year. Real markets swing, and a crash right before retirement hurts more than one 20 years out.
• Rounding. Dollar results are rounded to whole dollars. Contributions are added once per year (monthly × 12), and Coast Age is shown in whole years.

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