Investing
Investment growth calculator with fees and inflation
Compare gross, after-fee, after-tax and inflation-adjusted investment growth. Model contributions, withdrawals and a range of simulated outcomes.
Content updated . Assumptions reviewed .
Your inputs
Showing the example. Edit your inputs, then calculate.
Projected value
10,000 USD
Illustrative investment projection with the fee, tax and inflation assumptions you entered.
- Nominal
- 10,000
- After Fee
- 10,000
- After Tax
- 10,000
- Real Value
- 10,000
- Contributions
- 0
- Withdrawals
- 0
- Withdrawal Shortfall
- 0
- Fees
- 0
- Taxes
- 0
- P5
- 10,000
- P25
- 10,000
- P50
- 10,000
- P75
- 10,000
- P95
- 10,000
- Depletion Probability
- 0
Illustrative result from your inputs and the dated assumptions shown; not a forecast, recommendation or offer
KlarFort is not financial, investment, tax, or legal advice. Verify outputs before making material decisions. Read the disclaimer.
Personal and commercial use is free with credit to KlarFort. See usage and credit.
About this calculator
See how contributions, withdrawals, asset fees, tax assumptions and inflation change a projected investment balance. Choose whether the headline shows gross, after-fee, after-tax or real value.
Use volatility and simulation settings to explore a range of possible model outcomes alongside the constant-return projection. These scenarios describe the assumptions entered, not a forecast for a specific investment.
How to use this calculator
- Enter your starting balance, projection months, contributions and any regular withdrawals.
- Set the assumed annual return, contribution growth, asset fee, tax on positive gains and inflation.
- Choose the headline result and set volatility, path count and an optional simulation seed.
- Calculate, then compare each value basis, withdrawal shortfall, fees, taxes and simulated percentiles.
Understand your result
Gross value excludes fees and tax. After-fee value deducts the asset fee; after-tax value also applies the entered tax to positive monthly gains. Real value adjusts that after-tax balance for inflation.
The percentile results always describe simulated after-tax nominal ending balances, whichever headline mode is selected. Depletion counts paths with a zero closing balance at any point, even if later contributions rebuild it.
Questions about this calculator
What does the tax input represent?
It deducts the entered percentage from positive monthly gains after the fee. Losses produce no tax credit. This is a tax-drag illustration and does not model tax allowances, realization rules or a particular account.
Why does the simulated median differ from the constant-return result?
Simulations apply changing monthly returns drawn from the entered return and volatility assumptions. Their median is the middle modeled ending balance, which need not equal the constant-return path.
What happens if a withdrawal exceeds the balance?
The model pays only the available assets and reports the unmet amount as withdrawal shortfall. Contributions and withdrawals occur at month start, before that month's return, fee and tax.
Where do my figures go?
Your page calculations run in this browser. The API and connected assistants send the inputs supplied to them to our Cloudflare Worker. See Privacy.
How can I reproduce this result?
Use the same inputs and assumptions shown here. Simulation seeds reproduce the same paths. Read the calculation documentation.
Your calculation table
| Month | After Tax Balance |
|---|---|
| 1 | 10,000 |
| 2 | 10,000 |
| 3 | 10,000 |
| 4 | 10,000 |
| 5 | 10,000 |
| 6 | 10,000 |
| 7 | 10,000 |
| 8 | 10,000 |
| 9 | 10,000 |
| 10 | 10,000 |
| 11 | 10,000 |
| 12 | 10,000 |
Citable worked example
Investment growth calculator with fees and inflation: fixed public worked-example outputs using the calculator’s published default inputs. Compare gross, after-fee, after-tax and inflation-adjusted investment growth. Model contributions, withdrawals and a range of simulated outcomes. These illustrative figures are independent of visitor inputs and live market feeds. The table contains 12 rows and is available as CSV and JSON. Formula and assumptions reviewed 2026-09-07.
These are fixed public examples. Your calculation above does not change this table.
| Month | After Tax Balance |
|---|---|
| 1 | 10,000 |
| 2 | 10,000 |
| 3 | 10,000 |
| 4 | 10,000 |
| 5 | 10,000 |
| 6 | 10,000 |
| 7 | 10,000 |
| 8 | 10,000 |
| 9 | 10,000 |
| 10 | 10,000 |
| 11 | 10,000 |
| 12 | 10,000 |
Computed with KlarFort Calculators, https://klarfort.com/
Calculator reference: https://klarfort.com/tools/investment-growth-calculator/. Usage and credit.
Formula and assumptions
Each month: add contribution, pay withdrawal up to available assets, apply return, deduct an asset fee, then tax positive gains. Simulated monthly factors = exp(log(1 + annual return)/12 − volatility²/24 + volatility/√12 × Normal(0,1)).
- Contributions are made at the beginning of each month. Annual returns are effective rates converted to monthly compound factors. All figures use one entered currency.
- Tax applies to positive monthly gains only; there is no tax credit for losses. This is a tax-drag illustration using your rate, not jurisdiction-specific tax accounting.
- The annual fee is an effective asset deduction: monthly fee = 1 − (1 − annual fee)^(1/12). Downside percentiles always describe after-tax nominal terminal balances. A path is depleted if any closing balance is zero.
Assumptions reviewed:
Sources
- KlarFort calculation methodology. Free to use with the credit line; vintage 1.
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