Investment Return Calculator
Projects the future value of investments using compound growth with regular contributions. Supports multiple allocation scenarios and shows how asset mix, contribution amount, and time horizon affect final portfolio value.
Personal - Investment Return Calculator.xlsx
Excel (.xlsx) — No macros — Works in Excel, Google Sheets, LibreOffice
What This Spreadsheet Solves
- No projection of what current savings will grow to over time
- Unclear impact of increasing or decreasing monthly contributions
- Difficulty comparing conservative vs aggressive allocation outcomes
- Compound growth effects are unintuitive without modeling
- No tool to visualize the cost of delaying investment by N years
Who This Is For
- Individuals planning long-term investment contributions
- New investors understanding compound growth mechanics
- Financial advisors illustrating time-value-of-money to clients
- Pre-retirees evaluating if current savings pace meets goals
Inputs
- $Initial Investment
- $Monthly Contribution
- %Annual Return Rate
- #Investment Horizon (Years)
- %Allocation (Stocks/Bonds Split)
Outputs
- Projected future portfolio value
- Total contributions over the period
- Total investment gains (growth only)
- Year-by-year balance projection
- Comparison of 3 allocation scenarios
How Calculations Work
The calculator applies the compound interest formula with periodic contributions. Each month, the existing balance grows by the monthly return rate (annual rate / 12), and the contribution is added. The process repeats for the full horizon. For allocation comparisons, different stock/bond splits map to different expected return rates based on historical averages. The model also shows the cost of delay by comparing starting now vs starting N years later.
Example Use Case
Scenario: Initial investment: $15,000. Monthly contribution: $500. Expected annual return: 8%. Horizon: 25 years. Allocation: 80% stocks / 20% bonds.
Result: Projected value: $533,400. Total contributions: $165,000. Investment gains: $368,400 (69% of final value from growth alone). A 60/40 allocation at 6.5% return would yield $421,200. Delaying the start by 5 years reduces the 80/20 outcome to $339,100.
What You Get — 5 Sheets
Technical Details
Frequently Asked Questions
Are these returns guaranteed?
No. The model uses assumed return rates for projection purposes. Actual returns vary year to year. Use conservative estimates (5-7%) for planning and understand these are long-term averages.
Does this account for taxes?
The default model shows pre-tax growth. For taxable accounts, reduce the annual return by your estimated tax drag (typically 0.5-1.5% for a diversified portfolio).
How does allocation affect the return rate?
The CONFIG sheet maps common allocations to historical return ranges. More equity-heavy allocations have historically returned more but with higher volatility.
Can I model increasing contributions over time?
Yes. The CONFIG sheet has a contribution escalation setting where you can increase contributions by a fixed percentage or dollar amount annually.
Why does delaying 5 years make such a big difference?
Compound growth is exponential. Early contributions have the most time to compound. Each year of delay removes the most valuable compounding period, which disproportionately reduces the final value.
Download Investment Return Calculator
Ready to use immediately. Enter your data in the INPUT sheet, see results in OUTPUT.