# Have I saved enough for Coast FIRE?

Computes your Coast FIRE number: what you need invested today to reach your FIRE number by your retirement age with no more saving, and when you get there.

- Page: https://www.acalculator.org/finance/coast-fire-calculator
- JSON spec: https://www.acalculator.org/finance/coast-fire-calculator.json
- Version: 01562a886d68

## Default answer

Example with the default inputs (Your age 30, Retirement age 65, Yearly spending in retirement $50,000.00, Invested today $100,000.00, You save each month until you coast $1,500.00, Expected yearly return 7%, Prices rise each year by 3%, Safe withdrawal rate 4%): To coast to $1,250,000.00 by age 65, you need $329,443.28 invested today; you have $100,000.00, so you still need $229,443.28.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| age | Your age | Your age now. |
| retire | Retirement age | The age you want to retire and start spending your investments. |
| spending | Yearly spending in retirement | What you expect to spend each year once you retire, in today’s money. |
| saved | Invested today | What you have invested for retirement now. |
| monthly | You save each month until you coast | What you invest each month, in today’s money, until you reach Coast FIRE. Then you stop. |
| rate | Expected yearly return | The yearly return before inflation. It stays the same every year. |
| inflation | Prices rise each year by | The yearly inflation rate. The real return is (1 + return) ÷ (1 + inflation) − 1. |
| swr | Safe withdrawal rate | The share of your savings you plan to spend in the first year of retirement, often 4%. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| coast | Your Coast FIRE number today | FIRE number ÷ (1 + real return)^(years to retirement), in today’s money. |
| fire | Your FIRE number | Yearly spending ÷ safe withdrawal rate, in today’s money. |
| gap | Still needed today | The Coast FIRE number minus what you have invested, or 0 if you are there. |
| coastAge | You can coast from age | Your age when your investments first reach the Coast FIRE number, saving each month until then. |
| atRetire | Invested at retirement | Your investments at your retirement age, in today’s money. |
| status | Coast FIRE before retirement? | Shown when your investments do not reach the Coast FIRE number before your retirement age. |

## Method

Coast FIRE number = (yearly spending ÷ withdrawal rate) ÷ (1 + real return)^(retirement age − age), with real return = (1 + R) ÷ (1 + inflation) − 1; each month the balance grows at the monthly real rate plus your saving until it reaches that month’s Coast FIRE number.

## Assumptions

- All amounts are in today’s money: your saving and spending rise with prices.
- The return and inflation stay the same every year. Real returns go up and down.
- You stop saving once you reach Coast FIRE, and add nothing more until retirement.
- The withdrawal rate is a rule of thumb from past market returns, not a guarantee.
- Taxes, fees, and Social Security are not included.
- This is an estimate for planning, not financial advice.

## Worked examples

1. age = 30, retire = 65, spending = $40,000.00, saved = $50,000.00, rate = 7%, inflation = 0%, swr = 4% gives fire = $1,000,000.00, coast = $93,662.94, gap = $43,662.94. Source: hand calculation in content.mdx: 1,000,000 ÷ 1.07^35.
2. age = 30, retire = 65, spending = $60,000.00, saved = $100,000.00, monthly = $500.00, rate = 7%, inflation = 3%, swr = 4% gives fire = $1,500,000.00, coast = $395,331.94. Source: hand calculation in content.mdx: 1,500,000 × (1.03 ÷ 1.07)^35.
3. age = 30, retire = 80, spending = $24,000.00, saved = $50,000.00, monthly = $1,000.00, rate = 3%, inflation = 3%, swr = 4% gives fire = $600,000.00, coast = $600,000.00, coastAge = 75.833333. Source: hand calculation in content.mdx: at a 0% real return, (600,000 − 50,000) ÷ 1,000 = 550 months.
4. age = 40, retire = 60, spending = $40,000.00, saved = $500,000.00, rate = 7%, inflation = 2%, swr = 4% gives gap = $0.00, coastAge = 40. Source: hand calculation in content.mdx: $500,000 is above the Coast FIRE number, so you coast now.

## FAQ

### What is Coast FIRE?

Coast FIRE means you have invested enough that, with no more saving, growth alone would reach your FIRE number by your retirement age. From then on, your pay only has to cover your spending, not your retirement saving.

### How is the Coast FIRE number calculated?

Start with your FIRE number: yearly spending ÷ safe withdrawal rate. Then discount it back to today at the real return: Coast FIRE number = FIRE number ÷ (1 + real return)^(years to retirement). $1,000,000 needed in 35 years at a 7% real return is $93,662.94 today.

### What is the difference between FIRE and Coast FIRE?

With FIRE you have enough to stop working now. With Coast FIRE you have enough to stop saving now, but you keep working to pay for your life until your investments reach the full FIRE number at your retirement age.

### Why use a real return?

Your spending will rise with prices, so everything is in today’s money. The real return is (1 + return) ÷ (1 + inflation) − 1: a 7% return with 3% inflation is a 3.88% real return. If inflation is higher than the return, the real return is negative and the Coast FIRE number is higher than the FIRE number.

### What if my return is lower than I expect?

Then your investments grow more slowly and you may not reach your FIRE number by retirement. Returns are never guaranteed, so try a lower return, or a lower withdrawal rate, to see a more cautious number.

## Sources

- W. P. Bengen, "Determining Withdrawal Rates Using Historical Data", Journal of Financial Planning, October 1994.
- P. L. Cooley, C. M. Hubbard, D. T. Walz, "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable", AAII Journal, February 1998.
- Present value and the real rate of return: S. A. Broverman, Mathematics of Investment and Credit, chapter 1.
- U.S. Securities and Exchange Commission, Investor.gov compound interest calculator and formula. https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator