Practical guide
Understanding compound savings growth — sensitivity table
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.
Reading the starting balance sensitivity table
The tool evaluates the same model across a range of starting balance values while holding other assumptions constant. Choose a realistic low value, high value and number of points. Each row reports the same headline measure; the table is a set of conditional calculations, not a probability distribution or a forecast. Input-step rounding can make nearby rows equal.
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.
- Minimum starting balance
- 5,000 $
- Maximum starting balance
- 15,000 $
- Number of comparison points
- 5 points
- Monthly deposit
- 500 $
- Annual nominal return or APY
- 5 %
- Years invested
- 15 years
- Compounding periods per year
- 12 periods
- Annual inflation assumption
- 2.5 %
- Annual fee rate
- 0.25 %
Sensitivity analysis: 5 comparison points
Starting balance ranges from $5,000 to $15,000.
- Starting balance: $5,000: $141,055.14
- Starting balance: $7,500: $146,144.67
- Starting balance: $10,000: $151,234.2
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.
- Does the most favorable row show the most likely outcome?
- No. The table assigns no likelihood to any row. It shows how the result responds to the chosen assumption, and you remain responsible for selecting a plausible range.