Compound Interest Calculator
Project savings growth over time, optionally with recurring monthly contributions.
How this is calculated
Compound interest on principal: A = P × (1 + r/n)^(n·t).
Future value of recurring monthly contributions uses the annuity formula with the effective monthly rate derived from the compounding frequency.
Results assume contributions at month-end and a constant rate.
Frequently asked questions
Can I use this to calculate how much I need for retirement?
Yes — enter your current savings as the initial deposit, an expected annual return, and a monthly contribution to project growth over time. It doesn't account for inflation, taxes, or Social Security, so treat the result as a starting estimate rather than a full retirement plan.
Why do different calculators give me different retirement numbers?
Small differences in the assumed return rate or compounding frequency compound fast over a few decades — a 1% difference in rate can change a 30-year projection by tens of thousands. Neither this calculator nor most others factor in inflation or taxes by default, so use it to compare a few scenarios side by side rather than treating any single result as exact.