Annual Compound Interest Calculator
Calculate compound interest with annual compounding — interest is credited once per year. Common for long-term bond instruments and many simple retirement projections.
Your Inputs
$
$
Future balance
Contributed
Interest earned
How to Use
1. Enter your initial investment — the lump sum you start with today.
2. Add your monthly contribution.
3. Set your expected annual return and time horizon with the sliders.
4. Choose how often interest compounds.
Results and the growth chart update instantly.
2. Add your monthly contribution.
3. Set your expected annual return and time horizon with the sliders.
4. Choose how often interest compounds.
Results and the growth chart update instantly.
Calculation Method
Future value of a lump sum plus a stream of monthly contributions:
FV = P(1 + r/n)^(nt) + PMT × [((1 + rm)^m − 1) / rm]
P = principal, PMT = monthly contribution, r = annual rate, n = compounds/year, rm = r/12, m = months, t = years. Returns are user-assumed and not guaranteed.
FV = P(1 + r/n)^(nt) + PMT × [((1 + rm)^m − 1) / rm]
P = principal, PMT = monthly contribution, r = annual rate, n = compounds/year, rm = r/12, m = months, t = years. Returns are user-assumed and not guaranteed.
Source: Standard compound interest / annuity future-value formula.
Frequently Asked Questions
How does annual compounding differ from monthly?
With annual compounding interest is added just once per year, so it compounds less aggressively. At 8% over 30 years, annual compounding underperforms monthly by roughly 9%.
When is annual compounding the right model?
Long-term equity index assumptions are often quoted as annual averages, so annual compounding is a clean way to model "what if I earned X% per year".
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Investment Disclaimer: Calculations are estimates based on assumptions. Past performance does not guarantee future results. Investments involve risk, including potential loss of principal. SmartStockCalcs is not a registered investment advisor. For educational purposes only — consult a licensed financial advisor before making investment decisions.
Last updated: June 6, 2026