How it works
With monthly contributions and monthly compounding, the number of months n needed to grow from P to goal G is:
n = ln[(G·r + PMT) / (P·r + PMT)] / ln(1 + r)
- P = current savings
- G = goal amount
- PMT = monthly contribution (added at the end of each month)
- r = monthly rate (annual APY ÷ 12)
With no contributions the formula reduces to n = ln(G/P) / ln(1+r), and with a 0% rate it becomes simple division: n = (G − P) / PMT.
Example
Goal $25,000, current savings $5,000, contributing $400/month at 4% APY:
- Time to goal ≈ 45 months (about 3.8 years)
- Total you'll deposit out of pocket: $23,000 — interest covers the rest
What this calculator does not include
It assumes a constant APY and constant monthly contributions, compounded monthly. It does not model taxes on interest, contribution limits, or inflation. Results are estimates, not guarantees — bank APYs can change.
FAQ
What interest rate should I use?
Use the APY your bank actually pays. High-yield savings accounts have recently paid around 3-5% APY, while standard checking accounts pay close to 0%. If your money sits in a non-interest account, enter 0.
Why does my result say the goal is not reachable?
If you enter 0% interest and 0 monthly contribution with a goal above your current savings, no amount of time will get you there. Either add a monthly contribution or an interest rate.
Does this account for inflation?
No. The calculator works in nominal dollars. If your goal is far in the future, its real-world purchasing power will be lower — pair this with our inflation calculator to sanity-check the target amount.