FIRE & Independence

Coast FIRE Number by Age Calculator

Calculate the exact amount you need invested today so you never have to save another dollar for retirement.

Coast FIRE Number

Coast number

$277,851.72

Status

Need $127,851.72 more

You need $277,851.72 invested now to coast to retirement. You are $127,851.72 short.

Current savings alone will not reach your FIRE number by retirement. Continue contributing.

Coast FIRE Overview

Your savings vs coast number vs projected retirement portfolio

Current savings

$150,000.00

Coast number

$277,851.72

FIRE number (25x)

$1,250,000.00

Projected at retirement

$1,601,487.22

Key Metrics

Real return

4.39%

FIRE number

$1,250,000.00

Years to retirement

Projected at retirement

$1,601,487.22

How to use it

Enter your current age, target retirement age, current savings, expected nominal return, inflation rate, and desired annual spending in retirement. Use conservative return estimates rather than best-case scenarios.
Read the coast FIRE number first. This is the amount you need invested right now so that compound growth alone carries you to your retirement target without another dollar saved.
If you have already reached your coast number, the surplus tells you how much breathing room you have. If not, the gap shows exactly how much more you need to invest before you can stop contributing.
Compare your coast number against your FIRE number (25x spending). The coast number is always lower because it has time to grow. The further you are from retirement, the smaller the coast number relative to the FIRE number.
Re-run when your expected return changes by 1% or more, when inflation assumptions shift, or when your planned retirement spending changes. Track coast number progress alongside regular net worth updates.

AI Integrations

Contract, discovery endpoints, and developer notes for agent use.

Always available for agents

Tool contract JSON

https://aifinhub.io/contracts/fire-coast-number-calculator.json

Stable input and output contract for this exact tool.

Human review

People can use the browser page to sense-check outputs and charts, but agents should still execute against the contract and discovery endpoints.

/agent-tools.json - machine-readable tool index.
/llms.txt - human-readable model discovery guide.
/.well-known/webmcp.json - WebMCP capabilities manifest.
/.well-known/ai-plugin.json - plugin-style discovery manifest.

{
  "tool": "fire_coast_number",
  "current_age": 30,
  "retirement_age": 65,
  "current_savings": 150000,
  "expected_return_percent": 7,
  "inflation_percent": 2.5,
  "desired_annual_spending": 50000
}

Open tool contract JSON Open AI integrations guide

Expand developer notes

Agent playbook

Resolve Coast FIRE Number by Age Calculator from /agent-tools.json and open its contract before execution.
Validate inputs against the contract schema instead of scraping labels from the page UI.
Open the browser page only when a person wants to review charts, assumptions, or related tools.

Agent FAQ

Should ChatGPT, Claude, or another agent click through the UI?

No. Start with /agent-tools.json, then follow the tool's contract URL. The page UI is for human review, not parameter discovery.

When do tools show Quick and Advanced?

Every tool opens in Quick Start first. Advanced Controls keeps the same scenario, reveals more assumptions or diagnostics, and every tool keeps AI integrations inline below the instructions.

When should an agent still open the browser page?

Open it when a human wants to sense-check the output, review the chart, or keep exploring related tools after the calculation finishes.

Questions people usually ask

What is a coast FIRE number?

Your coast FIRE number is the amount you need invested right now so that compound growth alone — with zero additional savings — reaches your target retirement portfolio by your planned retirement age. Once you hit this number, you only need to earn enough to cover current expenses.

How is coast FIRE different from regular FIRE?

Regular FIRE means your portfolio is large enough to withdraw from today. Coast FIRE means your portfolio will grow to that size by retirement through compounding alone. Coast FIRE lets you stop saving aggressively years or decades before traditional FIRE.

What return rate should I use?

A 7% nominal return (roughly 4.5% real after inflation) is a common assumption based on long-term US stock market history. More conservative investors use 6%. Using anything above 8% nominal inflates the projection and understates the coast number.

Does this account for inflation?

Yes. The calculator adjusts both the FIRE target and the coast number for inflation. Your desired spending is in today's dollars, and the tool projects forward using your inflation assumption to find what that spending costs in future dollars.

What if I have not reached my coast number yet?

Keep contributing to investments. The tool shows the gap between your current savings and the coast number. As your savings grow and the coast number shrinks (because there is less time for growth), the two will converge.

Is my data stored?

No. All calculations happen in your browser. Nothing is stored or transmitted.