SaveSmart

Savings Calculator

See exactly how compound interest turns small monthly deposits into a meaningful balance.

Initial deposit

Monthly contribution

Expected annual return

Years to grow: 20

Growth over time

What you entered

Initial deposit: $1,000Monthly contribution: $300Expected return: 7%/yrYears: 20

1
Total months to compound
n = 20 years × 12= 240 months
2
Monthly return rate
r = 7% ÷ 12= 0.5833%
3
Compound monthly, adding your deposit each time
balance = balance × (1 + r) + $300.00, starting from $1,000.00, repeated 240×= $160,316.74
4
Total you contributed (not counting interest)
$1,000.00 + $300.00 × 240 months= $73,000.00
5
Interest earned
$160,316.74 − $73,000.00 contributed= $87,316.74

Result

Final balance: $160,317

Of your $160,317 final balance, $73,000 came from your own deposits and $87,317 came from compound interest — compounding did roughly 120% of the work your contributions did.

What regular monthly saving grows to at 7%

Each cell starts from zero and adds the monthly contribution shown, compounding at 7% a year. The last column is what you actually paid in over 30 years, so the difference is growth.

Monthly contribution	After 10 years	After 20 years	After 30 years	After 40 years	Contributed over 30 years
$100	$17,308	$52,093	$121,997	$262,481	$36,000
$250	$43,271	$130,232	$304,993	$656,203	$90,000
$500	$86,542	$260,463	$609,985	$1,312,407	$180,000
$1,000	$173,085	$520,927	$1,219,971	$2,624,813	$360,000
$1,500	$259,627	$781,390	$1,829,956	$3,937,220	$540,000
$2,000	$346,170	$1,041,853	$2,439,942	$5,249,627	$720,000

Compare the balance against contributions and the compounding share becomes obvious: $500 a month for 30 years puts in $180,000 and ends near $610,000, so roughly two thirds is growth. The final decade does most of the work, which is why the gap between the 30 and 40 year columns is larger than everything before it. Nothing here is adjusted for inflation - at 3% inflation, a balance 30 years out buys about 41% of what the same figure buys today. 7% is a common long-run assumption for a diversified portfolio, not a promise, and real returns arrive unevenly.

Why compounding matters

Each year's interest earns interest the following year. Over decades, this snowball effect can double or triple the total compared to simple interest.

Start early, beat luck

A 25-year-old saving $200/month at 7% beats a 35-year-old saving $400/month at the same rate by retirement age. Time in the market wins.

Frequently asked questions

How much should I save each month?

A common guideline is 20% of after-tax income (the 50/30/20 rule). If that's too much right now, start with whatever you can — even $50/month at 7% annual return grows to over $26,000 in 20 years thanks to compound interest.

How long does it take to double my savings?

Use the Rule of 72: divide 72 by your annual interest rate. At 6%, your money doubles in about 12 years (72 ÷ 6 = 12). At 10%, about 7.2 years. This rule works well for rates between 2% and 15%.

What interest rate should I use for projections?

High-yield savings accounts currently offer 4–5% APY. Stock market index funds have historically returned about 10% annually (7% after inflation). For conservative estimates, use your actual account rate. For long-term investment projections, 7% is a common inflation-adjusted figure.