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Investing scenario planner

Investment returns calculator

Model how a balance may change under three constant-return assumptions after contributions, withdrawals, fees, inflation, and a simplified deduction on positive modeled gains.

An illustration, not a forecast Returns are held constant and actual markets do not move this way. Results are educational estimates, not financial or tax advice or a guarantee of future returns.
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Investment details

All percentages are annual effective rates. Required fields are marked.

Investment inputs
$
$
years
%
Illustrative default only. Enter an assumption appropriate for your scenario.
pts
Sets conservative and optimistic rates below and above expected.
Additional inputs
%
%
%
%
%
Applied once at the end of the projection to positive cumulative modeled gains after fees. Read the important tax limitations.
Example: a $1,000 gross withdrawal with 20% estimated tax provides $800 in cash.
%
Applied only to withdrawals the modeled balance can fund. Using both tax-rate inputs may double-count taxes for some account types.
$
$
Month 1 is the first month of the projection.
%

Investment projection

Projected ending balance

Expected balance after estimated tax $0 after 20 years

Illustrative range: $0 to $0.

In today's dollars$0
Contributions$0
Withdrawals requested$0$0 funded
After-tax cash received$0
Estimated withdrawal tax$0
Net modeled growth$0
Estimated fees$0
Before estimated tax$0Projected ending balance before the terminal estimate
Estimated tax at end$0Simplified modeled-gains estimate
Conservative ending value
$0
Expected annual return
0%
Estimated tax timing
End of projection
Optimistic ending value
$0

Scenario balances over time

Three constant-return illustrations shown in nominal dollars.

The annual table below provides the same values without relying on the chart.

Annual projection

Show annual scenario and expected cash-flow detail
Annual balances and expected-scenario activity
YearStarting
balance		ContributionsGross
growth		FeesEst. tax
at end		Withdrawals
requested		Withdrawals
funded		Withdrawal
tax		After-tax
cash		Unfunded
withdrawals		Conservative
ending		Expected
ending		Optimistic
ending		Expected,
today's dollars
Tax and return limitations Neither tax estimate is a tax-return calculation. The terminal estimate assumes positive cumulative modeled gains after fees are taxable at the end of the projection and limits the deduction to the remaining modeled balance. The withdrawal estimate applies the entered rate to funded gross withdrawals without determining basis or account type. Both estimates ignore actual realization rules, holding periods, dividends, capital-gain distributions, loss offsets, tax brackets, penalties, and qualified distributions. They may materially differ from actual taxes. Constant annual returns also omit volatility and sequence-of-returns risk; actual outcomes may differ substantially.

How to use this investment return estimate

This calculator is useful for comparing long-term assumptions, exploring the drag from fees and inflation, and testing whether planned withdrawals may deplete a portfolio. It does not select investments or predict a market path.

  1. Enter the amount invested now and any recurring contribution.
  2. Choose a period and a reasonable expected annual return.
  3. Use the scenario spread or edit the conservative and optimistic rates directly.
  4. Add fees, inflation, withdrawals, and other assumptions under Advanced.
  5. Compare the expected result, illustrative range, annual path, and unfunded-withdrawal warning.

What the results mean

Nominal balance is the modeled account value in future dollars. Today's dollars discounts that value by the inflation assumption. Contributions and funded withdrawals are cash flows; net modeled growth is gross growth less estimated fees and modeled-gains deductions. The outer ending values form an illustrative range, not a probability interval.

Formula and model order

Annual effective assumptions are converted to equivalent monthly rates before the simulation:

monthly gross return = (1 + annual return)^(1/12) - 1
monthly fee rate = (1 + annual fee)^(1/12) - 1
monthly inflation rate = (1 + annual inflation)^(1/12) - 1
taxable modeled gain = max(0, cumulative gross growth - cumulative fees)
estimated terminal tax = min(pre-tax ending balance, taxable modeled gain × entered rate)

Each month the model adds any beginning contribution, applies gross growth or loss, deducts fees, adds any end contribution, and then deducts scheduled withdrawals. It floors the balance at zero and records any unfunded amount. Annual contribution increases take effect every 12 months. After the final month, the simplified tax estimate is deducted once from the remaining balance.

Worked example

Illustrative inputs: $10,000 starting balance, $500 contributed at the beginning of each month, 20 years, 7% expected return, a 2-point scenario spread, 0.5% annual fee, 2.5% inflation, and no tax estimate or withdrawals.

The calculator converts the 5%, 7%, and 9% annual scenario rates and the fee to monthly equivalents, then processes 240 months. The expected nominal ending balance is about $275,000, while its inflation-adjusted purchasing power is about $168,000. Small differences may result from display rounding.

Assumptions and limitations

  • Each scenario uses one constant annual effective return; volatility, market timing, and sequence risk are not modeled.
  • Fees apply monthly to modeled assets even when returns are negative.
  • Inflation changes purchasing-power reporting but does not change nominal cash flows.
  • Withdrawals cannot push the modeled balance below zero; unmet amounts are reported as unfunded.
  • All calculations use floating-point precision and round only for display or exported presentation.

Review the complete investment methodology for conventions shared across the site.

Frequently asked questions

What annual return should I enter?

Use a return consistent with the asset mix and time horizon you want to illustrate, after considering uncertainty. Historical averages are not guaranteed future returns.

Are conservative and optimistic scenarios confidence intervals?

No. They are constant rates set by the spread or by your direct edits. They do not express probabilities or forecast likely market boundaries.

Why is the real balance lower than the nominal balance?

When inflation is positive, future dollars have less purchasing power. The real balance expresses the expected scenario in today's dollars.

How are investment fees applied?

The annual effective fee is converted to a monthly rate and deducted from each scenario's balance after that month's gross growth.

Does the estimated tax represent taxes I will owe?

No. It is a deliberately simplified end-of-projection sensitivity applied to positive cumulative modeled gains after fees, not a tax estimate for any person, transaction, or account.

What happens if withdrawals exhaust the balance?

The balance remains at zero. The calculator tracks the requested amount that could not be funded and displays a warning.

How is estimated withdrawal tax calculated?

For gross withdrawals, the entered rate reduces the cash received. For after-tax cash requests, the calculator increases the account withdrawal so the requested cash remains after the estimate. Only funded withdrawals are included, and the result does not determine actual taxable basis or account-specific rules.

Glossary

Annual effective return
The yearly rate including compounding, converted here to an equivalent monthly rate.
Nominal value
A future-dollar balance without an inflation adjustment.
Real value
A balance discounted by modeled inflation and expressed in today's dollars.
Scenario spread
The percentage-point difference used to derive rates above and below expected.
Unfunded withdrawal
A requested withdrawal that exceeds the available modeled balance.