How to use
Enter what you start with, how much you add each month, the annual return you expect and how many years you will keep going. The future value updates as you type.
- For a single lump sum, set the monthly contribution to 0.
- For regular saving only, set the initial deposit to 0.
- Open “Year-by-year breakdown” to see contributions, growth and the balance at the end of each year.
Choose how the rate works:
- Investing (annual return): the default. Use it for stocks, ETFs and mutual funds, and for any rate quoted as an APY.
- Savings (APR, compounded monthly): use it when a bank quotes an APR that is compounded monthly.
APR vs. APY
An APR is a simple yearly rate. An APY includes the effect of compounding, so it shows what you actually earn in a year. A 6% APR compounded monthly equals about a 6.17% APY. When you compare savings accounts, compare APYs.
How it is calculated
Each month, the balance grows by the monthly rate and then the contribution is added:
balance at month end = previous balance × (1 + monthly rate) + monthly contribution
- Investing: monthly rate = (1 + annual return)^(1/12) − 1, so the balance grows by exactly the annual return each year.
- Savings: monthly rate = APR ÷ 12.
Examples
| Scenario | You put in | Future value | Growth |
|---|---|---|---|
| $10,000 once, 7% a year, 30 years | $10,000 | about $76,123 | about $66,123 |
| $10,000 plus $500 a month, 7%, 20 years | $130,000 | about $292,465 | about $162,465 |
| $500 a month, 7%, 30 years | $180,000 | about $584,726 | about $404,726 |
| $500 a month, 7%, 40 years | $240,000 | about $1,235,771 | about $995,771 |
| $10,000 in savings, 4.5% APR, 10 years | $10,000 | about $15,670 | about $5,670 |
Time makes the biggest difference. Saving $500 a month for 40 years instead of 30 adds $60,000 of contributions but about $650,000 to the final balance.
About past returns
Broad stock indexes have historically returned more than savings accounts over long periods, but past returns are not a promise. Returns have been negative in some years and flat over some 10-year stretches. Many people plan with 5–7% to leave room for fees, inflation and bad years.