Compounding pays interest on interest. Pick how often it compounds, optionally add a fixed contribution at the end of each period, and see the final amount split into what you put in and what growth added.
Formula & methodology
Principal growth: A = P(1 + r/n)^(n·t) where n is compounding periods per year. End-of-period contributions grow by the annuity factor PMT·((1+r/n)^(n·t) − 1) ÷ (r/n). At a zero rate everything degenerates to simple sums. Contribution timing convention: end of each period (documented, affects the result slightly vs beginning-of-period).
Worked examples
- 10,000 at 5% monthly, 10 years → 16,470.09
- Same, plus 100/month → about 31,998.32 — contributions of 12,000 became ~15,528 on their own
Limits
Real products charge fees and taxes and rates change; this projection assumes a constant rate. Estimates only, not investment advice.