Investment Portfolio Calculator

Before you enter your numbers

Weights must total 100%. Use returns on the same annual basis and enter the overall fee in percentage points. An expense input of 0.5 means 0.5% annually, not 50%. Keep fees out of the asset returns if you plan to subtract them in the fee field.

• Current portfolio value
• Monthly contribution
• Years invested
• Expected blended return

Input reference

• Portfolio value: The current balance committed to this goal. Use a recent statement and exclude money reserved for unrelated goals. This starting value is already invested, so do not also enter it as a recurring contribution.
• Monthly contribution: New money added at the end of each month. Convert annual saving to a monthly amount by dividing by 12. This page does not schedule skipped months or one-time deposits automatically.
• Years: The duration of the calculation in years. Longer periods give growth or withdrawals more time to operate. This is a chosen modeling horizon, not a prediction of an investment term or your lifetime.
• Portfolio fees: An annual percentage-point deduction from the gross return assumption. Check whether the source return already deducts this fee. One-time charges, trading costs and fixed account fees are not modeled by this field.

Formula and calculation method

Blended return = stock weight × stock return + bond weight × bond return + cash weight × cash return, using weights as fractions. The expense assumption is subtracted from that annual rate, and the net rate is used in the monthly future-value formula.

Worked example

For 60% stocks at 7%, 30% bonds at 3% and 10% cash at 2%, the blended gross assumption is 5.3%. A 0.3% annual fee reduces the planning rate to 5.0%. Changing the stock assumption changes the result even though the allocation is unchanged.

How to interpret the result

The result panel reports projected portfolio value, total contributions and estimated growth.

A weighted return is not a risk estimate. Correlations, market volatility, asset drift and the timing of rebalancing are absent. The model effectively applies a constant blended rate rather than tracking each holding through actual markets. Diversification does not guarantee against losses.

How the portfolio return is blended

The tool requires stock, bond and cash allocations to add to 100%. It multiplies each allocation by the return assumption for that asset class, adds the results, then subtracts the portfolio fee to create a blended net return for the projection.

This is a deterministic allocation model, not a Monte Carlo simulation. It shows how the expected mix changes the long-run projection, but it does not simulate year-to-year volatility, correlations or rebalancing paths.

Test weights and assumptions separately

First hold returns constant while changing the stock, bond and cash weights. Then restore the original weights and lower the asset-return assumptions. These tests answer different questions: the effect of allocation and the effect of less favorable markets. Changing both at once makes the source of the result harder to understand.

The model does not track a glide path from a working-life portfolio to a retirement portfolio. For that question, project the first phase, carry its balance forward and apply a new set of weights for the second phase. Rebalancing trades and their tax effects still remain outside the calculation.

Use allocation assumptions that add to a complete portfolio

The portfolio tool combines asset-class weights with separate expected returns and fees. Allocations should total 100%. A higher expected return from one asset class can increase the projected portfolio return, but it does not describe volatility, drawdowns or the probability of achieving that return.

Use conservative return assumptions and revisit the weights after major portfolio changes. If you rebalance periodically, the long-term average can differ from a simple buy-and-hold path, so treat the projection as an allocation scenario rather than a forecast.

Use The Result In The Next Calculation

Use the portfolio result to test how allocation and fees change a long-term projection. If you need account-specific tax treatment or a single-fund expense model, move to the brokerage, ETF, index-fund or mutual-fund calculator instead.