Compound Savings Calculator

Contributions vs. growth over the years, with the chart that explains compounding.

Compounding is interest earning interest. In the early years almost the whole balance is money you put in yourself, which is why the chart looks nearly straight at first and only bends later; the bend is the part that needs time rather than cleverness.

Be careful which rate you type. Deposit accounts are predictable and insured but modest: the national average savings rate was 0.37% and a 12-month CD 1.73% (FDIC national rates, 21 September 2026). Higher figures generally describe investments, where the return is not promised and the balance can fall as well as rise.

結果

結果はここに表示されます。

左側に数字を入力して「計算する」を押してください。入力した内容は保存されません。

具体的な例を見てみましょう

計算例

Starting amount$1,000
Monthly savings$200
Interest / return assumption (% per year)4%
Years20

結果の例

Ending balance$75,578 after 20 years at 4.0% (monthly compounding, deposits at month-end)

Total contributed$49,000 $1,000 start + $200 × 240 months

Growth from interest$26,578

Interest did 35% of the work. Stretch the years, not the monthly amount, and watch that share climb; time is the active ingredient.

A fixed rate for decades is a simplification: savings rates float and investments swing. Use it to compare scenarios, not to predict a balance.

Year	Balance
1	$3,485
2	$6,072
3	$8,764
4	$11,565
5	$14,481
6	$17,515
7	$20,673
8	$23,960
9	$27,381
10	$30,941
11	$34,646
12	$38,502
13	$42,515
14	$46,692
15	$51,038
16	$55,562
17	$60,270
18	$65,170
19	$70,270
20	$75,578

Monthly compounding, deposits at month-end, rate held constant: a comparison machine, not a prediction.

続けましょう Saving vs investing