Savings Goal Calculator

Estimate when your savings can reach a target using current savings, monthly deposits and a hypothetical fixed interest rate.

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How to Use the Savings Goal Calculator

Enter the target, existing savings and a monthly contribution. Choose a start date and optional annual rate; blank interest means zero. Interest is credited before each end-of-month contribution, on monthly anniversaries of the start date. Optionally enter a later target date to calculate the monthly deposit needed. All money is shown in USD without currency conversion.

Formula and Explanation

Monthly rate r = annual percentage / 100 / 12
B(next) = B(current) × (1 + r) + monthly deposit
After n months: B = B0 × (1 + r)^n + P × ((1 + r)^n − 1) / r
At r = 0: B = B0 + n × P
Required P = max(0, (target − B0 × (1 + r)^n) / annuity factor)

Monthly compounding means interest is earned on the opening balance, including earlier interest, before the deposit is added. New contributions exclude your starting balance; interest is the final balance minus that balance and new contributions. Target dates use monthly anniversaries, clamped to the last day of a shorter month. Only payments due on or before the chosen date count. Required deposits round upward to cents.

Rates are hypothetical fixed nominal annual rates, not guaranteed returns or forecasts. Taxes, fees, inflation, rate changes and daily bank-crediting rules are excluded. Balances are not rounded each month; displayed money rounds to cents. A 100-year horizon prevents unbounded projections. An unreached result means the goal is not reached within that horizon under these assumptions, not necessarily that it is mathematically impossible forever.

Worked Example

With a $1,200 target, $200 already saved, $100 deposited at each month end and 0% interest, ten deposits reach the target. New contributions are $1,000 and interest is $0. Starting January 31, 2026 gives a target date of November 30, 2026. At 12% nominal annual interest, $1,000 with no deposits becomes $1,020.10 after two monthly periods.

Frequently Asked Questions

When are monthly contributions added?

At the end of each monthly period, after interest on the opening balance. The first deposit occurs one month after the start date, not on the start date.

What if I already have enough saved?

The goal is reached at month zero on the start date. No new contributions or earned interest are needed in the time-to-goal result.

What happens with no interest or no deposits?

At zero interest the calculator simply adds each monthly deposit. If both deposits and interest are zero and the target is higher than current savings, the goal cannot be reached. Positive interest alone can grow a positive starting balance.

How does a target date change the calculation?

The separate required-deposit result counts monthly payment dates through your chosen date, then solves for the deposit that reaches the target. It does not replace your entered monthly amount or its time-to-goal result.