Compound Interest Calculator
Lump sum + optional periodic deposits (with growth). All values update instantly.
1) Principal & Interest
Leave empty to test deposits-only growth.
%
Nominal APR (not APY). We’ll handle compounding.
Months auto-normalize into years (12 → +1y).
2) Additional Deposits
%
Annual growth of each deposit; converted to per-period.
3) Results
Future value (final balance)
Total contributions
Interest earned
Effective annual rate (APY)
Deposit period rate (i)
Deposit growth per period (g)
# of deposits (N)
Step-by-step derivation
References
- Compound interest (lump sum): FV = P·(1 + r/m)^(m·t)
- Rate alignment: EAR = (1 + r/m)^m − 1; i = (1 + EAR)^(1/q) − 1
- Growing annuity FV (deposits with growth): FV = PMT · [((1+i)^N − (1+g)^N)/(i − g)] · (1+i)^(due?1:0); if i ≈ g, FV = PMT · N · (1+i)^(N−1) · (1+i)^(due?1:0)
Tip: Change any field — results update instantly.