What to save each month

How the goal calculator works

You choose a target amount, whether that amount is the final balance or the net growth on top of deposits, and a horizon in whole years or as a date. A date is counted in whole months from today.

The account is either a savings balance (interest, compounding, optional tax) or an investment (expected return, fund fee, optional inflation). The solver uses the same deposit timing and the same net-of-tax, net-of-fee growth as the other calculators.

The ending value is linear in the starting balance and the monthly top-up: final = alpha × balance + beta × monthly. Alpha and beta are the closed form of that monthly recurrence. The payment is rounded up to the next cent.

Formula

For a final-balance target, monthly = (target − alpha × balance) / beta, then rounded up to the next cent. If the balance already reaches the target with no further top-ups, the monthly amount is zero.

For a net-growth target, the goal is ending balance minus contributions. If extra deposits cannot increase that growth, because the rate is zero or fees dominate, the goal is reported as unreachable.

When the stock target is in today's euros, the nominal target is the amount you typed multiplied by (1 + inflation)^(years).

A worked example

A final balance of 100 000,00 € in 20 years, starting from 10 000,00 €, at 2.5% compounded monthly and no tax, needs 268,03 € each month.

That payment is rounded up to the next cent, so the replayed ending balance is 100 002,84 €, which meets the target.

Questions

What if I already have enough?

The monthly top-up is zero. The chart shows the current balance growing on its own.

Can a zero interest rate hit a growth target?

No. With no interest, the balance equals what you contribute, so net growth stays zero. A final-balance target can still be met by saving the difference.

How is a target date counted?

In whole months from today. A date in the past cannot be saved toward. A date less than one month away is too soon for a monthly top-up. Dates more than 80 years away are rejected.