Savings Goal Calculator — the deposit your target requires

How it works

The savings-annuity formula gives the balance from the deposit; this page inverts it algebraically: d = F·(r/k) ÷ ((1+r/k)^(k·y) − 1). Feed it the target F, the annual rate r, the deposits per year k, and the years y, and the answer is the end-of-period deposit that lands exactly on the target — the round trip back through the savings formula reproduces F to the cent. The outputs split the story: the total you would actually deposit, and the share of the target that compounding contributes. The years sweep prices procrastination directly: the same target at 10, 20, 30, and 40 years, with the required deposit collapsing as time does more of the work.

Worked example

The default inputs are LibreTexts' published retirement example: to have $200,000 in 30 years in an account earning 8%, deposited monthly. This calculator's ordinary-annuity math requires $134.20 a month; LibreTexts publishes $134.09, an $0.11 difference from rounding the intermediate monthly rate to three digits (0.08 ÷ 12 → 0.00667). Over 360 deposits the $134.20 is about $48,310 of your own money — roughly three-quarters of the target arrives as compounded interest, this calculator's split of the same method. Halve the horizon in the sweep and the required deposit far more than doubles: waiting is the expensive part.

Frequently asked questions

How much do I need to save per month to reach my goal?

Enter the target, rate, horizon, and frequency: the formula solves for the end-of-period deposit exactly. The anchor case: $200,000 in 30 years at 8% needs about $134.20 a month here (LibreTexts' rounding publishes $134.09) — and the same target in 15 years needs several times that, which the sweep shows for your own numbers.

Why does starting earlier lower the deposit so much?

Because early deposits compound the longest, and the divisor ((1+r/k)^(k·y) − 1) grows exponentially with years. Compounding's share of the target rises with the horizon, so the deposit — your share — shrinks faster than linearly as years are added.

How does the interest rate change the answer?

A higher rate shifts work from deposits to compounding: at 0% the deposit is simply the target divided by the number of deposits, and every point of rate above that cuts the requirement. The effect compounds with the horizon — rate matters little at 3 years and enormously at 30.

Will the answer definitely reach my target?

The arithmetic is exact for a constant rate; real accounts float. Treat the answer as the deposit that reaches the target IF the assumed rate holds — run the rate a point lower to see the margin a conservative plan needs. The uncertainty is the rate assumption, not the formula.

Should I count an existing balance toward the target?

Yes — grow it first, then aim for the remainder: the compound-interest calculator gives your current balance's future value at the same rate and horizon; subtract that from the goal and solve here for the smaller target. The future-value calculator does both pieces together.

What frequency should I pick?

The one you'll actually automate. Monthly matches most paychecks and starts each dollar compounding soonest; the difference between frequencies at the same annual total is small next to rate and years, so consistency beats optimization here.

How accurate is this, and what does it exclude?

Exact for end-of-period deposits at a constant rate. It excludes rate changes, taxes on interest, fees, missed or extra deposits, and inflation — a target set in today's dollars buys less by the time it is reached, so long-horizon goals deserve an inflation cushion on top.