What the calculator shows
Enter a starting amount, monthly contribution, effective annual rate, years and inflation. The dated FDIC national savings rate provides an editable starting reference, while the result separates contributions from growth and shows today’s purchasing-power value.
Calculation method
The entered effective annual rate is converted to an equivalent monthly rate. Growth is applied each month before the month-end contribution. Today’s value divides the future amount by the entered annual inflation factor over the selected years.
Inputs to confirm
Replace the reference with the account APY or a documented planning assumption. Add taxes, fees, rate changes and withdrawal rules when comparing a specific bank or investment product.
Worked savings example
With $10,000 initially, $500 at each month end, a 0.38% effective annual rate and 10 years, the model returns $71,529.26: $70,000 contributed and $1,529.26 growth. Discounting at 2% gives $58,678.91 in today’s dollars.
| Change | Nominal balance | Interpretation |
|---|---|---|
| Higher monthly contribution | Higher | More money supplied by the saver |
| Higher steady rate | Higher | Assumption, not a guarantee |
| Higher inflation only | Unchanged | Today’s-dollar value falls |
Separate contribution growth from purchasing-power growth
The result shows nominal future balance, total money contributed, modeled growth and today’s-dollar value. Those figures answer different questions and should not be collapsed into one promised return.
Effective annual rate is converted before monthly modeling
The calculator converts the entered effective annual rate into an equivalent monthly rate, applies growth, then adds the month-end contribution. This preserves the entered annual yield more accurately than simply dividing it by 12.
Timing makes starting money and monthly deposits behave differently
The starting amount is exposed to every modeled month, while each later deposit has less time to grow. Increasing contributions can therefore matter more than small rate changes, especially in short scenarios.
A savings reference is not an investment forecast
The FDIC national savings rate is a dated editable reference. A bank APY can change and an investment return includes volatility, fees and tax that this steady path does not model. Inflation only discounts the result; it does not alter nominal account growth.
| Result | Meaning | Important limit |
|---|---|---|
| Total contributed | Starting amount plus deposits | No growth included |
| Modeled growth | Future balance minus contributions | Steady rate, no tax or fees |
| Today’s dollars | Future balance discounted by inflation | Not a guaranteed purchasing power |
Primary source
Federal Reserve Bank of St. Louis / FDIC: national savings rate