Target savings estimate

Calculate the required monthly contribution in whole yen to reach a target amount in the selected years.

If calculation UI does not appear, reload with JavaScript enabled. Related context links below remain available.

Calculation basis and official references

Reviewed on:

Formula basis

For each candidate contribution, the calculator runs its beginning-of-month savings schedule and tests final balance against the target. In maturity-tax mode it deducts cumulative interest×tax rate; 20.315% is the default.

Calculation method

Uses binary search to find the smallest whole-yen monthly contribution whose simulated ending balance reaches the target under the entered term, rate, compounding, and maturity-tax choices.

Exclusions and checks required

  • The reverse calculation uses no initial principal or bonus contribution and assumes fixed beginning-of-month deposits.
  • The NTA source supports only the 20.315% default, not maturity tax, monthly compounding, binary search, or rounding.
  • The assumed return is not guaranteed; product taxation, fees, price changes, and rate changes are excluded.

Example input:：Targeting JPY 10 million after 10 years

annualRate
1.2
rounding
floor
years
10
targetMan
1000
compounding
monthly
taxMode
maturity
taxRate
20.315

The amount is the smallest whole-yen contribution under the implementation's beginning-of-month and maturity-tax assumptions.

Official references

FAQ

Who is this calculator for? Target savings estimate

Calculate the required monthly contribution in whole yen to reach a target amount in the selected years.

What values should I enter?

Applies to: Savings / The minimum whole-yen monthly contribution is found using binary search.

How should I interpret this estimate?

Uses binary search to find the smallest whole-yen monthly contribution whose simulated ending balance reaches the target under the entered term, rate, compounding, and maturity-tax choices.

How to use

  1. Enter your input values and press Calculate.
  2. Review the result and compare it with expected context.
  3. For each candidate contribution, the calculator runs its beginning-of-month savings schedule and tests final balance against the target. In maturity-tax mode it deducts cumulative interest×tax rate; 20.315% is the default.

Official references