36 calculators for every money decision
Growth, retirement, taxes, debt, portfolio sizing, bonds and cash. All math runs in your browser; nothing is stored or sent anywhere.
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Growth and Compounding · Retirement · Taxes and Fees · Debt · Portfolio and Stocks · Bonds and Cash
Growth and Compounding
How money grows, how fast it doubles, and what inflation quietly takes back.
Compound Growth
Compounding means your returns earn returns. Small monthly amounts become large sums given enough time, which is why starting early matters more than starting big.
Savings Goal
This solves for the monthly contribution that, with growth, reaches your goal by the deadline. Your current savings grow too, so they shrink the monthly amount required.
CAGR
Compound annual growth rate is the single steady rate that would turn the start into the end over that period. It smooths out the bumpy path an investment actually took.
Rule of 72
Divide 72 by the return to estimate doubling time, or by the years to find the return needed. It is a mental shortcut that is remarkably accurate for rates between 4% and 12%.
Inflation Adjuster
Inflation erodes purchasing power quietly. At 3% a year, prices roughly double every 24 years, so a plan that ignores inflation overstates what your money will actually buy.
Real Return
The exact formula is (1 + nominal) divided by (1 + inflation) minus 1, which is slightly less than simple subtraction. Real return is what actually grows your purchasing power.
Lump Sum vs DCA
This compares investing everything today against splitting it into 12 equal monthly buys, assuming a steady return. When expected returns are positive, lump sum usually wins on average, but dollar cost averaging reduces the pain of bad timing.
Simple vs Compound Interest
Simple interest pays only on the original principal; compound interest pays on principal plus accumulated interest. The gap between the two is the entire magic of long-term investing.
Retirement
How much you need, how long it lasts, and whether you can coast.
Retirement Number
This divides your spending by your withdrawal rate. The 4% rule comes from historical US market data over 30 year retirements. It is a planning guideline, not a guarantee: longer retirements, bad early markets, or high fees can call for a lower rate.
Years to Financial Independence
Financial independence arrives when your portfolio can cover your spending at a safe withdrawal rate. Your savings rate is the biggest lever: it both grows the portfolio faster and shrinks the target it must reach.
Safe Withdrawal Income
This is the reverse of the retirement number: portfolio times withdrawal rate equals sustainable annual income. It shows what a nest egg is actually worth as a paycheck.
How Long Will My Money Last
The balance grows each year, then spending is withdrawn, until it runs out. If growth covers the withdrawals, the money can last indefinitely at these assumptions.
401(k) Match Value
An employer match is an instant guaranteed return on your contribution. Contributing at least enough to capture the full match is almost always the first investing move to make.
Traditional vs Roth
Traditional defers tax to withdrawal; Roth pays it up front. If your tax rate is identical in both periods, the two end up exactly equal, so the real question is whether your rate will be higher now or later.
Coast FIRE
Coast FIRE means your current portfolio, left alone with zero new contributions, would grow into your full retirement number by retirement age. Once you hit it, saving becomes optional rather than mandatory.
RMD Estimate
Required minimum distributions divide your balance by an IRS life expectancy divisor that shrinks with age. This uses approximate divisors from the Uniform Lifetime Table, so treat it as an estimate and confirm the exact figure with the current IRS table.
Taxes and Fees
The quiet costs that compound against you.
Fee Drag
Fees compound against you just like returns compound for you. A difference that looks tiny, like 0.05% versus 1%, can quietly consume a large share of your lifetime gains.
Tax Drag
Paying tax on gains every year, as in a taxable account with heavy turnover, slows compounding. This shows the gap versus letting the same money grow untaxed until the end.
Capital Gains Tax
Gains held over a year get preferential long-term rates; shorter holdings are taxed like ordinary income. Simply waiting past the one-year mark can meaningfully cut the tax bill.
Tax-Equivalent Yield
Muni interest is generally free of federal tax, so its yield punches above its number. This shows the taxable yield you would need to match it in your bracket.
Pro-Rata Rule
A backdoor Roth conversion is taxed on the pre-tax share of all your IRA money combined, not just the new contribution. Large existing pre-tax balances make most of the conversion taxable.
Advisor Fee Cost
A percentage-of-assets fee is charged on the whole portfolio every year, in good markets and bad. Over decades the compounded cost can be several times the annual fee that gets quoted.
Debt
What loans really cost and when paying them down beats investing.
Loan Payoff
Each month interest accrues on the remaining balance and your payment covers it before touching principal. If the payment does not exceed the monthly interest, the loan never shrinks.
Extra Payment Impact
Extra payments go straight to principal, so every future month accrues less interest. The savings compound, which is why even modest extra amounts shorten loans dramatically.
Mortgage Payment
This is principal and interest only; taxes, insurance, and HOA fees come on top. Early payments are mostly interest, and the principal share grows slowly over the term.
Payoff vs Invest
Paying down debt earns a guaranteed return equal to the APR; investing offers a higher but uncertain expected return. The math favors the higher rate, but the guaranteed one carries zero risk.
Portfolio and Stocks
Sizing positions, harvesting dividends, and keeping the mix on target.
Position Size
Position size comes from the dollars you are willing to lose divided by the loss per share if your stop is hit. Sizing by risk, not by conviction, is what keeps single trades from wrecking accounts.
Dividend Income
Portfolio times yield equals annual dividend income. Chasing the highest yields often backfires; very high yields frequently signal a struggling company about to cut its payout.
Dividend Reinvestment Growth
Reinvested dividends buy more shares, which pay more dividends, on top of price growth. This is an approximate model with steady growth rates, so treat it as illustrative.
Rebalancing
Rebalancing sells whatever grew past its target and buys whatever fell behind, which quietly forces you to sell high and buy low. Once or twice a year is plenty for most portfolios.
Allocation by Age
These rules subtract your age from 110 or 120 to suggest a stock percentage, with the rest in bonds. They are rough starting points; your actual mix should reflect your timeline and how you handle downturns.
Yield on Cost
Yield on cost measures the dividends you collect against what you originally paid. For long-held dividend growers it can climb far above the current market yield.
Bonds and Cash
Pricing bonds, sizing rate risk, and keeping cash honest.
Bond Price vs Yield
A bond price is the present value of its coupons plus its face value, discounted at the market yield. When yields rise above the coupon, the price falls below face, and vice versa.
Duration Impact
Duration approximates rate sensitivity: price change is roughly duration times the rate move, in the opposite direction. It is a linear estimate that gets less accurate for large rate swings.
CD / T-Bill After-Tax Yield
Treasury interest is exempt from state income tax, so in high-tax states a T-bill can beat a CD with the same stated yield. Always compare after-tax numbers.
Emergency Fund Size
Three to six months of essential expenses suits most people; closer to twelve makes sense for variable income or a single-earner household. Keep it in high-yield savings or T-bills, not in stocks.
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How these work
Every tool here uses standard, published finance math. The growth calculators compound monthly or annually as labeled: each period the balance grows by the periodic rate, then contributions are added. The retirement number is annual spending divided by the withdrawal rate, so $60,000 at 4% requires $1.5 million. The loan tools amortize month by month, charging interest on the remaining balance before applying the rest of the payment to principal. The bond calculator discounts each coupon and the face value back to today at the market yield. Fee and tax drag run the same projection twice at different net rates and show the gap.
All of these are educational and illustrative, not advice. They assume steady returns, steady contributions, and unchanging rules, which real life never delivers. They ignore taxes unless a tool says otherwise, and the tax tools themselves use simplified flat rates rather than full bracket schedules. The RMD divisors are approximations of the IRS Uniform Lifetime Table. Historical US stock returns have averaged roughly 7% after inflation over long stretches, but returns are not guaranteed and arrive unevenly. Use these calculators to compare scenarios and understand the levers, not to predict an exact future balance, and confirm tax questions with the current IRS rules or a professional.