Savings growth: how much comes from deposits?
Separate money you contribute from illustrative compound growth.
A future balance can look impressive without showing where it came from. Split it into the money you contributed and the growth assumed by the model before comparing savings plans.
Start with a transparent scenario
Suppose you begin with $10,000, add $200 at the end of each month and model a constant 4% annual rate for ten years. Your regular deposits total $24,000, so the total cash contributed is $34,000 including the opening balance.
| Scenario over 10 years | Total contributed | Illustrative end balance | Growth before tax and fees |
|---|---|---|---|
| $0.00 monthly | $10,000.00 | $14,908.33 | $4,908.33 |
| $100.00 monthly | $22,000.00 | $29,633.31 | $7,633.31 |
| $200.00 monthly | $34,000.00 | $44,358.29 | $10,358.29 |
| $300.00 monthly | $46,000.00 | $59,083.27 | $13,083.27 |
Change what you can control separately
Increasing the monthly deposit and increasing the assumed return are different choices. One changes money you plan to contribute; the other changes an uncertain modelling input. To understand each effect, change only one at a time and keep the original scenario for comparison.
Understand deposit timing
This model compounds monthly and then adds the regular deposit at the end of the month. A beginning-of-month deposit would earn an extra month of growth. If two calculators disagree, check that timing assumption before concluding that one is mathematically wrong.
Keep the future number in perspective
The result is before tax, fees and inflation. A balance measured in future dollars does not tell you exactly what it will buy. It also assumes no withdrawals and a steady rate. Real savings products and investments may use different compounding methods or variable returns.
Build a useful comparison
Give saved calculations descriptive names such as “$200 monthly at 4%” instead of “best plan”. If you have a target date, test whether the contribution is realistic in your actual budget. Avoid increasing the assumed return simply to make an unaffordable target appear reachable. The calculator is not selecting an investment or predicting performance.
Explore a savings scenario · Read the monthly-compounding assumptions
Questions or corrections?
Send the relevant page and a non-sensitive example through our contact form. Read our calculation methodology to see the scope of the model.