複利計算機
compound• 初期投資・毎月積立・年利回り・期間から満期資産を計算。 • 複利で増える資産の推移をグラフで表示。
Work back from a target
Enter the amount you want to reach and see the monthly contribution it takes. Uses the starting amount, rate and period above.
Enter a target to get the monthly contribution and the time it takes.
満期時の予想資産
106,639,017
総元本 70,000,000 · 総利益 +36,639,017
毎月末積立・月複利を前提に計算した税引前の名目額です。税金・手数料・物価上昇は反映していません。
Years for the principal to double
The rule of 72 — divide 72 by the annual return for a quick estimate.
The exact formula is ln2 ÷ ln(1+r). This assumes the principal sits alone with no contributions, and excludes tax and fees.
Frequently asked questions
What is the difference between monthly and annual compounding?
How often the interest is folded back into the principal. Annual compounding does it once a year, monthly does it every month, so the same nominal 7% grows slightly faster monthly (about 7.23% effective). This calculator assumes end-of-month contributions with monthly compounding.
How much do I need to save each month to hit a target?
Enter the figure under Work back from a target and the required monthly amount appears. At 7% over 10 years, reaching 100 million takes about 580,000 a month. Stretch the same target to 20 years and it drops to about 190,000 — time does far more work than the amount does.
What is the rule of 72?
Divide 72 by the annual return and you get roughly how many years it takes to double: 8% gives 72÷8 = 9 years, 6% gives 12. The exact formula is ln2÷ln(1+r), and between 6% and 10% the two differ by about a tenth of a year — close enough for mental arithmetic. The table above shows both.
Are taxes and inflation included?
No. These are pre-tax nominal figures. In practice tax on interest and dividends plus fees come off the top, and inflation erodes what the same amount can buy. With 3% inflation, a 7% nominal return is closer to 4% in real terms.
What annual return should I enter?
There is no single right answer, and past figures do not guarantee future returns. What is certain is that the result grows steeply as you raise the rate, so it is safer to run both a conservative and an optimistic figure and read the outcome as a range rather than a number.