Free workbook · Step-by-step guide
Investment Growth Projector
Excel template.
Choose a starting balance, monthly contribution, assumed annual return, and time horizon. This free Excel investment spreadsheet projects year-end balances and separates money contributed from modeled growth, using monthly compounding.
By Devon Coombs, CPA, MBA · Assistant Teaching Professor of Finance and Faculty Director of Real Estate Finance, Santa Clara University · Guide reviewed October 10, 2026
How do I project investment growth with monthly contributions?
- Replace the example starting balance and monthly contribution with your planned amounts.
- Enter an assumed annual nominal return and a horizon of up to 40 years. The worksheet divides the annual rate by 12.
- Review the annual balances and the split between contributions and growth. Contributions are modeled at the end of each month.
- Try lower and higher return assumptions. Compare the results before using any one scenario in a plan.
Worked example
A ten-year contribution example
- Starting balance
- $10,000
- Monthly contribution
- $500
- Assumed nominal annual return
- 6%, compounded monthly
- Time horizon
- 10 years
The projected ending balance is about $100,134: $70,000 contributed and $30,134 of modeled growth. This is a calculation under fixed assumptions, not a forecast.
Know what the model leaves out
The projection holds the return constant and ignores fees, taxes, inflation, losses along the way, and changing contributions. A 6% nominal annual rate compounded monthly is different from a 6% effective annual return. Real returns vary and can be negative.
Common questions
Are contributions made at the beginning or end of each month?
At the end of each month in this workbook. A beginning-of-month contribution would earn one additional month of modeled growth; use consistent timing when comparing calculators.
Is the projected investment balance adjusted for inflation?
No. It is a nominal dollar projection. A future dollar may buy less than a dollar today. Model inflation separately and avoid interpreting the projection as guaranteed purchasing power.
Build the next part of your plan
Built as an Excel workbook. If you import it into Google Sheets or Numbers, check formulas and formatting before relying on the results. Devon Coombs Academy is an independent educational resource; these downloads are not an official Santa Clara University product or personalized financial advice.