Your results will appear here

Enter your assumptions and calculate to see the estimated result and supporting details.

How this calculator works

Choose Contribution required (enter years → estimate monthly contribution) or Time required (enter monthly contribution → estimate months to goal).

Enter goal amount, current savings, and APY. Monthly deposits are modeled at the end of each month. Annual progress is shown when meaningful.

Formula / methodology

rm = (1 + APY)^(1/12) − 1
FV_current = current × (1+rm)^N
C = (goal − FV_current) / [((1+rm)^N − 1) / rm]
(for rm = 0: C = (goal − current) / N)

APY is an effective annual yield. The equivalent monthly rate is (1 + APY)^(1/12) − 1 — not APR / 12.
Mode A solves the ordinary annuity contribution directly. Mode B simulates month-by-month (grow, then end-of-month deposit) up to 1,200 months.
If current savings alone already meet the goal, required contribution is $0. Unreachable cases (for example 0% APY with $0 contributions) return a clear limitation.

Goal $10,000, current savings $2,000, 4 years, 0% APY → required monthly contribution is $166.67 (exactly $8,000 / 48).

Same goal and current savings with $200 monthly contributions at 0% APY → 40 months to goal.

APY is a user-supplied effective annual yield — not a live bank quote.
Monthly contributions occur at the end of each month.
Time horizons use whole years in contribution mode; time mode caps at 100 years.
Taxes, fees, and inflation are not modeled.