Portfolio Risk Calculator guide
Portfolio expected return is weight-averaged, while risk also depends on how assets move together. Correlation below one can reduce portfolio volatility.
Historical estimates can fail during stress when volatility and correlation change simultaneously.
How to use the portfolio risk calculator
- Enter current amounts: Use current, documented values from the same relevant period.
- Enter assumptions: Use realistic rates, percentages, periods, and costs where applicable.
- Review the full result: Review the primary estimate together with its supporting measures.
- Stress-test risk: Model less favorable timing, value, cost, or rate assumptions.
Formula and variables
The estimate applies the entered values and assumptions to the stated formula.
Variance = w₁²σ₁² + w₂²σ₂² + 2w₁w₂σ₁σ₂ρ- Inputs — Entered values
- The amounts, percentages, or periods supplied to the calculator.
- Result — Calculated output
- The estimate produced by applying the formula to the entered values.
Worked example: portfolio risk calculator
A user enters a representative set of values and assumptions.
- Key inputs
- Amounts, percentages, periods, and costs
- Apply the stated formula.
- Include all relevant entered values and constraints.
- Compare the result with an alternative scenario.
Result: Expected portfolio return, volatility, Sharpe ratio, and diversification benefit.
Use the estimate as a planning input and verify important decisions with current records or qualified guidance.
Understanding your results
Primary estimate
Expected portfolio return, volatility, Sharpe ratio, and diversification benefit.
Risk measures
Use supporting payment, leverage, cost, and cash figures together.
Assumptions
- Entered rates and costs remain constant.
- Payments and cash flows occur on schedule.
Limitations
- Taxes, legal terms, accounting treatment, and transaction-specific costs may differ.
- Future values, timing, and rates are uncertain.
Common mistakes
- Reviewing only the headline result.
- Ignoring relevant costs, timing, or supporting measures.
- Using optimistic timing or value assumptions.
- Treating an estimate as a guaranteed outcome.
Practical use cases
Compare scenarios consistently
Change one assumption at a time or enter each alternative using the same basis.
Plan cash requirements
Estimate funds needed before committing.
Planning and decision guide
Stress-test the assumptions
Use comparable horizons and return definitions for all inputs.
Review the important risks
Stress-test higher volatility and correlation near one.
Verify the source values
Consider concentration, liquidity, drawdown, taxes, and non-normal returns beyond standard deviation.
Frequently asked questions
Why does correlation affect risk?
It determines how much asset gains and losses offset each other.
Must weights total 100%?
Yes for this fully invested two-asset model.
What is diversification benefit?
The reduction from weighted standalone volatility to modeled portfolio volatility.
Is Sharpe ratio a forecast?
No. It is an estimate based on entered expected return and volatility.
Sources and review
- Asset allocation and diversification — U.S. Securities and Exchange Commission. Accessed 2026-07-10.
Reviewed 2026-07-10.