Use a balance you can verify and a contribution you can sustain through ordinary months.
Build your wealth
Understand what consistency and time can do.
02 / PlanFind your freedom
Put a number and a timeline on your FIRE goal.
03 / ResetGet debt-free sooner
See the impact of every extra payment.
The toolkit
A clearer answer starts here.
FIRE calculators & simulators. Each one is built to be deep, fast, and free.
FIRE planning
FIRE Number Calculator
Find the portfolio size you need to retire early — and your years to freedom.
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Build wealth
Compound Interest Calculator
Project how an initial amount plus monthly contributions grows over time.
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Retirement
4% Rule Calculator
How much you can safely withdraw, and how long your money lasts.
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FIRE planning
Coast FIRE Calculator
See if you can stop saving and let compounding finish the job.
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Build wealth
Savings Goal Calculator
What to put away each month to hit a target by a date — and the price of starting late.
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Debt freedom
Debt Payoff Calculator
Avalanche vs snowball — which clears your debt faster and cheaper.
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Build wealth
S&P 500 Backtest Simulator
"What if I'd invested back then?" Test any window with real total returns, dividends, inflation, CAGR and drawdowns.
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Retirement
Access Retirement Money Before 59½
Rule of 55, Roth ordering and five-year clocks, 457(b), HSA, 72(t) — screened against your own accounts, with the exact reason each route passes or fails.
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Retirement
Rule of 55 Calculator
Does the separation-from-service exception reach your plan? And what would a rollover cost you?
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Retirement
Roth Withdrawal Order
Which layer your withdrawal actually comes from, and which of the two five-year clocks governs it.
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Retirement
Can I Retire On…?
What $300k to $5M actually pays per month — and how long it lasts. 15 amounts answered.
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Build wealth
Live Off Dividends Calculator
Find your dividend crossover year, and compare dividends-only vs the 4% rule side by side.
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Debt freedom
Early Mortgage Payoff Simulator
See the interest and years you save with extra monthly payments.
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FIRE planning
Lean FIRE vs Fat FIRE
Compare both targets and the years to reach each.
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FIRE planning
Barista FIRE Calculator
Semi-retire with part-time income — the gap math done right.
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FIRE planning
Coast FIRE by Age
Your coast number at every age, from 20 to retirement.
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FIRE planning
Savings Rate to FI
How your savings rate sets your retirement date.
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Build wealth
Rule of 72
How fast your money doubles at any return.
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Build wealth
Real Hourly Wage
What your time is really worth per hour.
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Retirement
How Long Will My Money Last?
See how long savings last — and how sequence-of-returns risk moves the date.
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Retirement
Retire on $X / Month
The nest egg a target monthly income needs, with or without Social Security.
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Retirement
Net Worth Percentile
See where your net worth ranks and what share of Americans have $1M+.
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Retirement
Retire Abroad
What your portfolio buys in another country — with Medicare and tax reality built in.
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Retirement
Retirement Spending by Age
What retirees actually spend, by age and category, from BLS survey data.
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Retirement
Can You Retire at 62?
Model the five-year bridge to full Social Security for any nest-egg size.
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Retirement
Early Retirement Bridge
Model the gap years between your last paycheck and Social Security, account by account, with the 10% priced only where it applies.
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Build wealth
Investment Fee Calculator
See the compounding you lose to fund and adviser costs.
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No calculators match your search.
Go beyond a smooth curve
What if you’d invested back then?
Test any window with real total returns, dividends, inflation, CAGR and drawdowns. Explore the S&P 500 Backtest Simulator with data from 1928–2025.
Explore the backtestYour next chapter, in numbers
Compound Interest Calculator
Adjust any input and watch your projection update live.
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Total Future Value
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Total invested
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Interest earned
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Growth Over Time
Invested
Total Value
Monthly compounding, with contributions at the end of each month. A constant-return illustration, not a market forecast.
My Compound Growth Projection — Financial Depth
financialdepth.com
Quick Summary (TL;DR)
- Compound interest pays you on your principal and on prior interest — growth accelerates over time.
- Example: $10k + $500/mo at 7% for 30 yrs → ~$691k, from just $190k contributed.
- Time matters more than timing — starting earlier beats saving more later.
- Formula:
FV = P(1+i)n + PMT·[((1+i)n−1)÷i]
How Compound Interest Builds Wealth
Compound interest is the quiet engine behind every FIRE journey. Unlike simple interest, which pays only on your original principal, compounding pays you on your principal and on the interest you've already earned. Each period's gains join the base that earns the next period's return, so growth curves upward instead of climbing in a straight line — and the effect gets dramatic over decades.
This calculator projects future value with the formula FV = P(1+i)n + PMT · [ ((1+i)n − 1) / i ], where P is your initial investment, PMT is the monthly contribution, i is the monthly return (annual rate ÷ 12), and n is the number of months. Contributions are added at the end of each month and earn returns in subsequent months.
Worked example: Start with $10,000, add $500/month, and assume a 7% annual return for 30 years. You'd contribute $190,000 of your own money, but end with roughly $691,150 — meaning compounding did more of the heavy lifting than your deposits did. Stretch the timeline to 40 years and the gap widens even further. Time, not timing, is the FIRE investor's biggest advantage.
Frequently Asked Questions
What is compound interest?+
It's the interest you earn on both your original principal and on the interest already accumulated. Because each period's gains are added to the base that earns the next period's return, growth accelerates over time — the engine behind long-term investing and FIRE.
How is growth with monthly contributions calculated?+
Future value equals the initial amount compounded over the period, plus the future value of your stream of monthly contributions. We compound monthly using FV = P(1+i)ⁿ + PMT[((1+i)ⁿ − 1) / i], where i is the monthly rate and n is the number of months.
What return rate should I assume for FIRE planning?+
Many in the FIRE community model a long-run nominal return near 7% for a diversified stock portfolio, or roughly 4–5% after inflation. Use a conservative figure for planning, since actual returns vary year to year.
Decision guide
How to read a compound-growth projection
The large future-value number is only the starting point. Separate money you contributed from growth, check whether the return is nominal or inflation-adjusted, and compare more than one scenario before treating the result as a plan.
Run a lower-return case. Long horizons amplify even a one-percentage-point difference.
Compare future value with future spending needs and purchasing power after inflation.
What this model includes
- Monthly contributions and compounding
- A split between invested principal and growth
What to add outside the model
- Taxes, fund fees, and changing contribution levels
- Market volatility and the order of annual returns
Calculation standard: Formula details, source policy, tests, and limitations are documented in the FinancialDepth methodology. Reviewed July 18, 2026.