How this calculator works
This is the compound interest formula solved for the contribution amount instead of the ending balance. Tell it your goal, what you’re starting with, your expected rate, and your timeline, and it works backward to tell you how much to save each period.
The formula
growth = (1 + r/n)^(n×t) requiredContribution = (target − principal × growth) / ((growth − 1) / (r/n)) If r = 0: requiredContribution = (target − principal) / (n × t) If requiredContribution ≤ 0: you're already on track — no more contributions needed.
Worked example
Reaching $50,000 in 5 years, starting from $0, at 4% annual interest compounded monthly:
- Required monthly contribution: $754.16
- Checking the math: contributing $754.16/month for 60 months at 4% compounded monthly grows to almost exactly $50,000
Frequently asked questions (FAQ)
How is this different from the compound interest calculator?
Our compound interest calculator tells you how much a contribution amount will grow to. This one runs the math backwards: you tell it how much you want to end up with, and it solves for the contribution needed to get there.
Where should I keep money I'm saving toward a goal?
For a goal within a few years, a high-yield savings account or CD keeps your principal safe while earning some interest. For longer-term goals (retirement, a decade or more away), many people accept more risk for potentially higher growth — but that also means the rate you enter here is far less certain.
What if I already have enough saved to hit my goal without contributing more?
This calculator checks for that: if your current savings, growing on their own at your chosen rate, are projected to exceed your goal, it reports that you're already on track and shows the projected surplus instead of a required contribution.
Does a higher starting balance really reduce how much I need to save?
Yes, meaningfully — money you already have compounds for the entire time horizon, doing some of the work for you. Try comparing a $0 starting balance against a $5,000 one for the same goal to see how much the required monthly contribution drops.
Should I use a conservative or optimistic rate assumption for a savings goal?
For a firm deadline (like a house down payment in 2 years), use a conservative rate close to what a savings account or CD actually pays. For a flexible, long-term goal, a more optimistic rate might be reasonable, but remember actual investment returns aren't guaranteed and can vary year to year.