Advanced Coast FIRE Calculator

7% is the standard for long-term stock market investing. Here's the math: S&P 500 has averaged about 10% nominal returns over the past century. Subtract 3% for inflation, and you get 7% real return.

If you're cautious, use 5%. If you're optimistic (or investing more aggressively), try 10%. The scenario presets let you compare both instantly — just click Optimistic or Conservative at the top of the calculator.

The two scenarios use different assumptions:

Optimistic: 10% return, 2% inflation, 4% withdrawal rate. This assumes strong market performance and low inflation — good for best-case planning.

Conservative: 5% return, 4% inflation, 3.5% withdrawal rate. This assumes weaker returns and higher inflation — good for stress-testing your plan.

If you're on track in the Conservative scenario, you're probably in good shape. Custom mode lets you set any values you want.

Toggle on Couple Mode to enter both partners' ages, retirement dates, and savings balances.

You'll see two calculation options: • Combined: Merges both savings accounts and uses the younger partner's timeline. This makes sense if you'll share expenses in retirement. • Separate: Shows individual Coast FIRE numbers side by side. Useful if you're tracking progress independently.

Most couples use Combined since they'll be splitting retirement costs anyway.

Higher inflation means you need more money. Here's why: if inflation averages 3%, $1 million today will only buy $412,000 worth of stuff in 30 years.

The calculator handles this by showing everything in today's dollars. Your Coast FIRE number is what you need today — the actual future amount will be higher, but it'll have the same purchasing power.

If you're worried about inflation, try the Conservative scenario (4% inflation) to see how it affects your target.

The quick calculator on the homepage uses fixed assumptions: 7% return, 3% inflation, 4% withdrawal rate. That's fine for a rough estimate.

But real financial planning needs flexibility. Maybe you want to see what happens with 5% returns. Maybe you're planning with a spouse. Maybe you want a more conservative withdrawal rate for early retirement.

This advanced calculator lets you test all of that. You can compare scenarios, adjust every parameter, and make sure your plan holds up under different conditions.

Nominal returns are the raw market growth — about 10% historically for the S&P 500. Real returns subtract inflation (typically 3%), giving you roughly 7%. Always use real returns in Coast FIRE calculations, because your goal is measured in today's purchasing power.

If you use nominal returns by mistake, your Coast FIRE number will be too low — you'll think you need less than you actually do. This calculator uses real returns by default to prevent this common error.

Yes — set your retirement age to 50 and see how it changes your number. Early retirement has two effects: fewer compounding years (higher Coast number) and a longer withdrawal period (consider using a 3.5% withdrawal rate instead of 4% for extra safety).

The advanced calculator is ideal for early retirement planning because you can adjust the withdrawal rate downward. At 3.5%, your target nest egg increases by about 14%, but you gain significantly more security over a 40+ year retirement horizon.