Compound Interest & FIRE Calculator

FIRE (Financial Independence, Retire Early) is a lifestyle movement focused on aggressive saving and investing to achieve financial independence — the point at which your investments generate enough passive income to cover your living expenses permanently.

Your FIRE number is calculated by dividing your annual expenses by your safe withdrawal rate. Using the 4% rule, multiply your annual expenses by 25. Example: $50,000/year in expenses × 25 = $1,250,000 FIRE number.

The 4% rule comes from the Trinity Study (1998) and has historically held up over 30-year retirement periods. For longer retirements (40-50 years), many FIRE practitioners use 3-3.5% to be conservative. Adjust the withdrawal rate slider to model different scenarios.

When inflation is toggled on, the calculator shows your future balance in today's purchasing power (real dollars). For example, $2M in 30 years at 3% inflation is equivalent to about $820,000 in today's money.

Compound interest means you earn interest on your interest. Each month, returns are calculated on your total balance (original investment + accumulated growth), creating exponential growth over time. Starting early is the single biggest advantage.