Omikuji Tools Life & Calc

Compound Interest & Savings Calculator

Future value of a starting amount plus monthly contributions with compound interest, shown year by year with a chart. Reverse mode finds the monthly deposit needed for a target.

✨ Features

  • Future value and interest earned from a starting amount, monthly contributions, annual rate and years
  • Year-by-year table of contributions, value and interest, with a stacked chart
  • Reverse mode: the monthly deposit needed to reach a target; optional tax on gains
  • Recalculates as you type; copy results, copy the table as CSV or share a URL

🪄 Use cases

Planning regular investing

What 300 a month at 5% for 20 years becomes, split into contributions and growth.

Retirement or education goals

Find the monthly amount needed to reach a target in a given number of years.

Comparing rates

See how much 1% versus 5% changes the final value.

Taxable vs tax-free accounts

Compare the after-tax result with the tax-free one.

🔒 Privacy

Amounts are processed in your browser and never sent to a server. Only when you shorten a share URL is that URL (including the input) sent to the shortening service.

❓ FAQ

What is compound interest?

Interest is added to the balance, and the next period's interest is calculated on the new, larger balance. Over long periods this snowballs, which is why starting early matters.

Why do monthly and yearly compounding differ?

With monthly compounding interest is added twelve times a year, so the same annual rate yields slightly more than yearly compounding.

When are deposits assumed to be made?

At the end of each month. Depositing at the start of the month gives a slightly higher result.

How is tax calculated?

20.315% (the Japanese rate on investment gains) is applied to the interest earned (value minus contributions) and shown as the after-tax value. Untick it for tax-free accounts.

🔗 Related tools

Age Calculator Date Calculator BMI & Calorie Calculator Price Calculator Slope & Angle Calculator To-Do List Unit Converter & Calculator Bill Splitter Japanese Zodiac & Age
%
years