How the required contribution is calculated
This calculator first projects what your current savings alone will grow to by your deadline, then figures out what level monthly contribution — added on top and left to grow at the same rate — would make up the remaining gap to your goal.
The formula, in plain language
Contribution = (Goal − Current × (1 + r)^n) × r / [(1 + r)^n − 1]
- Goal — your target amount
- Current — what you've already saved
- r — the monthly return rate (annual rate ÷ 12, as a decimal)
- n — the number of months until your deadline
Worked example
Suppose your goal is $50,000, you already have $5,000 saved, you have 10 years, and you expect a 6% annual return:
- Your current $5,000 alone is projected to grow to about $9,097 in 10 years
- Remaining gap to close: roughly $40,903
- Required monthly contribution: $249.59
Try these exact numbers in the calculator above to see the full year-by-year path to your goal.