Practical guide
Understanding monthly investing planner — compare initial investment
Everyday editorial team · GEOINNOVATION CO., LTD · Published · Updated
What this calculation is for
Compound growth shows how a starting balance and recurring deposits may develop over time. Comparing a deposit increase with a rate increase can reveal which assumption has more influence. Keep savings-account assumptions separate from risky investment-return assumptions.
How the method works
The starting balance grows at a monthly-equivalent rate and deposits are added at month-end. Where compounding frequency is editable, it converts a nominal annual rate using that frequency. Detailed tools also show proportional annual fee effects and purchasing power after the entered inflation rate.
A worked example
A $1,000 opening balance plus $100 each month contains $2,200 of contributions after one year. An ending balance above $2,200 represents modeled growth; it should not be confused with the full account balance.
Assumptions and real-world differences
Rates, contributions and fees are held constant. Taxes, changing bank terms, investment losses and irregular deposit timing are not automatically included. A CD penalty is a separate alternative rather than a deduction from its normal maturity amount.
Comparing two initial investment assumptions
The baseline and alternative calculations change initial investment while keeping the remaining model inputs the same. This isolates that particular assumption rather than comparing two completely different plans. Read both detailed outcomes and the B-minus-A difference in the headline’s units. A larger number is not automatically better: a larger cost and a larger savings balance have opposite interpretations.
Reproduce this tool’s example
These fixed example inputs are independent of edits you make above. Enter them in this tool to reproduce the result, then replace them with your own assumptions.
- Initial investment
- 10,000 $
- Monthly investment
- 500 $
- Assumed annual return
- 6 %
- Contribution period
- 15 years
- Compounding periods per year
- 12 periods
- Inflation assumption
- 2.5 %
- Annual investment fee
- 0.25 %
- Alternative initial investment
- 12,500 $
Scenario B result: $171,878.58
Scenario A: $165,969.43. Projected ending balance.
- Scenario A main result: $165,969.43
- Scenario B main result: $171,878.58
- Numeric difference (B − A), in result units: 5,909.15
Frequently asked questions
- Is an advertised APY the same as a nominal rate?
- No. APY already reflects compounding; check the field description before entering a quoted rate.
- Are deposits made at the beginning of the month?
- These projections use month-end deposits unless the specific tool states otherwise.
- Can I also change other assumptions in the alternative?
- This one-factor comparison deliberately holds them fixed. Use the two-scenario version when rates, costs, timing or several household inputs all differ.