Coast FIRE Calculator

When You Can Stop Saving for Retirement

Coast FIRE represents the point where your existing retirement savings, growing untouched, will reach your retirement target by your planned retirement age. Once you reach Coast FIRE, you could theoretically stop saving for retirement—your investments coast to the finish line on their own.

This milestone doesn't mean retirement; it means freedom from mandatory retirement saving. You still need income for current expenses, but that income no longer needs to include retirement contributions. Coast FIRE opens options—career changes, reduced hours, or lower-paying but more fulfilling work.

Let compound interest finish the job.

The Coast FIRE Concept

Coast FIRE asks: How much must I have now so that compound growth alone reaches my retirement number?

Future Value = Present Value × (1 + return)^years

Working backward: Coast FIRE number = Retirement Target / (1 + return)^years to retirement

Calculating Your Coast FIRE Number

For traditional retirement at 65 with $1,500,000 target:

Younger ages require dramatically less due to compounding time.

Factors in Coast FIRE Calculation

Expected return rate: Higher returns lower the coast number Target retirement age: Later retirement extends growth time Retirement spending needs: Lower needs mean lower target Inflation adjustment: Real vs. nominal calculations matter

The calculator handles all these variables.

Return Rate Sensitivity

Return assumptions significantly impact Coast FIRE:

$1,500,000 target, 30 years to grow:

1% return difference changes the number by 25-30%.

Inflation Considerations

Nominal calculations ignore inflation's impact on purchasing power.

Real return = Nominal return - Inflation

7% nominal return with 3% inflation = 4% real return

Using real returns provides inflation-adjusted Coast FIRE numbers.

Coast FIRE vs. Full FIRE

Coast FIRE: Enough invested to stop contributing, but keep working for expenses Lean FIRE: Enough to retire with minimal lifestyle FIRE: Enough to retire maintaining current lifestyle Fat FIRE: Enough to retire with enhanced lifestyle

Coast FIRE is typically the first milestone reached.

Life After Coast FIRE

Reaching Coast FIRE enables options:

Barista FIRE: Part-time work covering expenses (often with benefits) Career pivot: Pursue lower-paying but meaningful work Reduced hours: Work less without jeopardizing retirement Entrepreneurship: Take risks knowing retirement is secured

The freedom comes from separating current income from retirement saving.

The Math of Coasting

$200,000 invested at 35, targeting $1,500,000 at 65:

$200,000 × (1.07)^30 = $1,522,000 ✓

This person has reached Coast FIRE—existing investments will grow to the target without additional contributions.

Partial Coast FIRE

You may reach partial Coast FIRE where some contribution is still needed:

Target: $1,500,000 at 65 Current investments (age 40): $200,000 $200,000 grows to (25 years, 7%): $1,085,000 Shortfall: $415,000 Required additional saving: ~$500/month to cover gap

As investments grow, required contributions decrease until reaching full Coast FIRE.

Combining with Other Goals

Coast FIRE focuses on retirement, but other goals may require continued saving:

Children's education Early retirement (before traditional age) Home purchase Healthcare bridge before Medicare

Coast FIRE for traditional retirement doesn't address these.

Risk Considerations

Coast FIRE assumes returns materialize. Risks include poor sequence of returns (bad early years hurt more), lower-than-expected average returns, inflation exceeding assumptions, and early forced retirement (less coasting time).

Conservative assumptions provide safety buffer.

Using the Calculator

Enter current age, target retirement age, current retirement savings, target retirement amount, and expected return.

The calculator shows:

• Your Coast FIRE number
• Whether you've reached it
• Remaining amount needed
• Years until Coast FIRE at current savings rate
• Sensitivity to different return assumptions

Model scenarios: What if you retire at 60 instead of 65? How does a higher return assumption change the number? What's your Coast FIRE number for a more modest retirement?

Use results to understand when saving for retirement becomes optional.

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Coast FIRE represents a liberating milestone—the point where your retirement is funded by time and compound interest rather than ongoing sacrifice. The calculator reveals your Coast FIRE number and whether you've reached it. This knowledge opens options: continue saving to retire early, or redirect income toward other goals knowing retirement is handled. Either way, Coast FIRE provides freedom.