Fat FIRE Calculator

What Makes Fat FIRE Different

Fat FIRE targets financial independence with a higher standard of living. Instead of optimizing for minimal spending, it assumes a larger annual budget, more travel, premium healthcare, and higher lifestyle flexibility. The required portfolio is therefore much larger, and the timeline often depends more on high earnings and strong savings rates than on frugality.

Because spending is higher, the plan is more sensitive to withdrawal rate and inflation assumptions. Small changes in these inputs can translate into hundreds of thousands of dollars in target portfolio size. This calculator helps you evaluate those trade-offs explicitly.

Core Formula

Let $S$ be your baseline annual spending and $b$ a lifestyle buffer. The adjusted spending $\mathrm{S\text{'}}$ is:

The Fat FIRE target $F$ is then:

The lifestyle buffer captures extra spending for upgrades, travel, philanthropy, or cushion against unexpected costs.

Timeline Estimation

The timeline uses a real return model: your portfolio grows by the real return (nominal return adjusted for inflation), then you add annual contributions. The model stops once your balance exceeds the target. While simplified, this approach is useful for comparing scenarios quickly.

Withdrawal Rate Scenarios

Fat FIRE plans often use more conservative withdrawal rates to protect against large spending commitments. The table below shows how your target changes at 3%, 3.5%, and 4% withdrawal rates.

Assumptions and Limitations

This model assumes steady returns, constant spending, and consistent contributions. It excludes taxes, investment fees, and estate planning costs, which can be significant for high-net-worth households. It also assumes your portfolio is invested in a diversified mix and that your withdrawal rate is sustainable over your retirement horizon.

Fat FIRE plans often involve concentrated assets (real estate, private businesses, or equity grants). If your wealth is illiquid or concentrated, a simple portfolio model may understate risk. Consider adding a larger buffer or using a lower withdrawal rate if your assets are less diversified.

Planning Considerations

High spending can amplify volatility. A downturn early in retirement can force larger withdrawals relative to portfolio size, increasing sequence-of-returns risk. Many Fat FIRE planners keep a larger cash reserve or a bond allocation to stabilize withdrawals.

Another consideration is lifestyle inflation before retirement. If your spending is trending upward, use a higher baseline or buffer so your target reflects your desired future lifestyle rather than your current one. The calculator is most useful when you revisit it periodically and update your inputs as your goals evolve.