Retirement / FIRE Calculator

About the Retirement / FIRE Calculator

A retirement calculator answers two questions in one: how much do I need to stop working, and when will I get there if I keep saving at my current pace? Together they're the foundation of every personal-finance plan. Most calculators only answer the second; this one answers both.

The number you're solving for is called your FIRE number — short for Financial Independence, Retire Early. It's the size of investment portfolio that can fund your lifestyle indefinitely. The shortcut for calculating it is the 4% rule, derived from the 1998 Trinity study: withdrawing 4% of a portfolio in the first year (25× your annual spending), then adjusting for inflation, historically lasted at least 30 years in most of the periods studied — a guideline, not a guarantee. Spending $50,000 a year? Your FIRE number is $1.25M. Spending $80,000? $2M.

Why the chart matters more than the headline. The trajectory line shows where you actually are versus where you need to be. If it crosses the dotted "FIRE" reference line before your target retirement age, you can retire earlier. If it doesn't cross at all by age 100, you need to save more, earn more, or accept a higher withdrawal rate.

Pick your withdrawal rate honestly. 4% is the default and works in most historical scenarios. Use 3.5% if you're retiring before 50 (longer time horizon → more sequence-of-returns risk). Use 5% only if you're flexible enough to cut spending in bad years or have other income — Social Security, a pension, part-time work.

The two levers that actually move the FI age. Increasing your monthly contribution by $500 typically pulls FI in by 3-5 years. Increasing your expected return from 6% to 8% (e.g. moving from a 60/40 to 80/20 portfolio) typically pulls it in by 4-7 years. Cutting your target spending by $10,000/year is by far the most powerful — it lowers the FIRE number by $250,000 directly. This is general education, not financial advice.

How to use it

1. Enter your current age and target retirement age. 65 is the default; FIRE practitioners often aim for 40-55.
2. Enter what you've already saved. Combine 401(k), IRA, brokerage — anything investable.
3. Enter your monthly contribution. Use what you actually save today, not what you wish you saved.
4. Set your expected annual return. 7% is a common long-term assumption for stocks; use about 5% for an after-inflation figure.
5. Enter your annual spend in retirement. Use today's dollars, and pair it with an after-inflation return so the two match.
6. Choose your safe withdrawal rate. 4% is the Trinity-study default; 3.5% is safer for early retirement.
7. Read the verdict. The chart shows when (and if) your portfolio crosses the FIRE line — that's your earliest possible retirement age.

Frequently asked questions

What do the default inputs show in the retirement calculator?

Starting at age 30 with $15,000 saved, $800 a month and a 7% return, the projected balance at 65 is about $1,613,436. With $50,000 of annual spending at a 4% withdrawal rate, the FIRE number is $1.25 million, which this plan reaches at age 62 — 32 years from now.

Does the retirement calculator adjust for inflation?

Not separately — it grows your savings at the return you enter and compares the result with a FIRE number based on the spending you enter. To keep everything in today's dollars, use an inflation-adjusted (real) return; the field's hint suggests about 5% instead of 7%.

Why does the retirement calculator keep projecting past my target retirement age?

It projects to age 100 so it can still find the age you reach your FIRE number even if that's after your target. It assumes you keep contributing every month until then and does not model withdrawals, so the curve shows when you could stop, not how the money is spent down afterward.

How do I include Social Security or a pension in the retirement calculator?

There's no separate field, so subtract the yearly income you expect from your annual spend before entering it. For example, $50,000 of spending minus $20,000 of expected Social Security leaves $30,000, which at 4% is a $750,000 FIRE number. Social Security is US-specific and its amount depends on your claiming age — this is general education, not financial advice.

What does "short" mean on the retirement calculator's balance-at-retirement card?

It's the gap between your FIRE number and the projected balance at your target retirement age. If the projected balance meets or beats the FIRE number, the card shows "On track" instead.

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