Calculator
See how steady saving grows over time
Start with a sum, add a little each month, pick a growth rate and watch what it becomes, in dollars today and after inflation.
Data last checked . Every source is listed below.
What it could grow to in 20 years
$10,000 to start and $200 a month at 7% a year becomes $144,573, of which $86,573 is growth.
Where it goes
- What you start with$10,0007%
- Money you add$48,00033%
- Growth$86,57360%
- The same amount in today's dollars
- $88,229at 2.5% inflation
- What you put in
- $58,000$10,000 to start and $200 a month
- Growth added
- $86,573
- Yield over one year
- 7.23%growth added monthly
- Time to double with no new money
- 9.9 years
Adding $100 more each month would grow the total by about $52,093 over 20 years. Starting 5 years later, with everything else the same, would leave you with $52,691 less.
For information only: not advice, a recommendation or an offer. We take care, but our sources can lag and so can we, so a figure may be out of date. Official figures come from lenders, plans, the IRS or Social Security.
What moves the number
The few things that change the answer the most, in plain terms.
- Time
- Growth earns growth. The longer money stays, the more of the final total comes from growth rather than deposits. An earlier start usually adds more growth than larger deposits made later.
- The growth rate
- A few points of difference compound into a large gap over decades. Real returns also vary year to year, which a single average rate hides.
- Regular deposits
- Over short periods, how much you add each month usually matters more than the rate.
- How often growth is added
- Monthly or daily beats yearly, but on ordinary rates the gap is small compared with the rate and the years.
- Inflation
- Prices rise, so a dollar later buys less than a dollar today. The in-today's-dollars figure shows what the total could buy in terms of today's prices.
The working
Step by step, with the numbers from the starting example, so you can check it on paper.
- Each year the growth rate is 7%, added monthly, so each period earns 0.5833% on the balance at the time.
- Over a full year that works out to a yield of 7.229%.
- With nothing added, $10,000 would grow by a factor of (1 + 7% ÷ 12) to the power 240, which is $40,387 after 20 years.
- Each month $200 more goes in at the end of the month and then grows too. Over 20 years that is $48,000 of deposits.
- Adding it up, the total is $144,573: $58,000 that you put in and $86,573 of growth.
- Dividing by (1 + 2.5%) for each of the 20 years gives $88,229 in today's dollars.
Try a different case
Each opens the calculator with the numbers filled in.
What we assumed
Where a number is an example, we say so.
- Our estimateThe growth rate stays the same every year. Real investments rise and fall, and a savings account rate changes with the market.
- Our estimateMonthly deposits are added at the end of each month.
- Our estimateNo taxes, fees or withdrawals are taken out. Taxes on growth, fund fees or account fees would lower the result.
- Our estimateInflation is a flat yearly rate you can change. It is not a forecast.
- Checked sourceThe maths of compounding is exact: a balance grows by a factor of (1 + rate ÷ periods) each period. Our unit tests check the monthly simulation against that formula.
Sources
- Checked sourceConsumer Financial Protection Bureau, Regulation DD (Truth in Savings), Appendix A to Part 1030: how banks turn a quoted rate and its compounding into the yield actually earned. Data year 2026, checked 2026-11-04.