Compound Interest Calculator
Compounding frequency
Future value
$31,998.32
Total interest earned: $9,998.32
Growth summary
- Total contributions
- $22,000.00
- Total interest earned
- $9,998.32
- Effective annual rate
- 5.116%
- Years to grow
- 10 × Monthly
Growth summary: $10,000.00 → $31,998.32
Yearly breakdown
| Year | Start balance | End balance | Interest earned | Contributions |
|---|---|---|---|---|
| 1 | $10,000.00 | $11,739.50 | $539.50 | $1,200.00 |
| 2 | $11,739.50 | $13,568.01 | $628.50 | $1,200.00 |
| 3 | $13,568.01 | $15,490.06 | $722.05 | $1,200.00 |
| 4 | $15,490.06 | $17,510.44 | $820.39 | $1,200.00 |
| 5 | $17,510.44 | $19,634.20 | $923.75 | $1,200.00 |
| 6 | $19,634.20 | $21,866.60 | $1,032.41 | $1,200.00 |
| 7 | $21,866.60 | $24,213.23 | $1,146.62 | $1,200.00 |
| 8 | $24,213.23 | $26,679.91 | $1,266.68 | $1,200.00 |
| 9 | $26,679.91 | $29,272.79 | $1,392.88 | $1,200.00 |
| 10 | $29,272.79 | $31,998.32 | $1,525.54 | $1,200.00 |
Compound Interest Calculator — Grow Savings Year by Year
Compound interest is growth on growth: every period your balance earns interest, and the next period earns interest on the new, larger balance. This free calculator shows what your savings become — enter a starting principal, annual rate, years to grow, compounding frequency and an optional regular contribution to see the future value, total interest earned, effective annual rate and a year-by-year breakdown of balances, interest and contributions.
Compare yearly versus daily compounding on the same rate, test what an extra $100 per period does over decades, and watch small rate differences snowball. Every calculation runs locally in your browser with no signup, and any scenario can be shared with a link that reproduces it exactly on another device.
How compounding works
Each period the balance grows by the periodic rate and then the end-of-period contribution is added (ordinary annuity). More frequent compounding means more growth periods per year — the same nominal rate earns more when compounded daily than yearly.
FV = future value · P = initial principal · i = annual rate / 100 / periods per year · N = total periods · C = contribution added at the END of each period. With a 0% rate the balance grows linearly: P + C·N.
How it works
- Enter your starting balance — what you invest on day one, from $0 to $10,000,000.
- Set the annual rate (0–25%) and how many years the money grows (1–50).
- Pick yearly, quarterly, monthly or daily compounding — higher frequency earns more at the same rate.
- Optionally add a regular contribution each period and watch the year-by-year breakdown.
Daily vs yearly compounding
Frequency matters: 5% compounded monthly behaves like 5.116% a year, and daily compounding earns a little more still. Switch frequencies above on identical inputs to see the gap.
Frequently asked questions
What is compound interest?
Interest earned on both your original balance and previously earned interest. Each period's growth becomes part of the next period's base, so growth accelerates over time.
Which compounding frequency should I use?
Match your account: most savings accounts compound daily, many bonds pay semi-annually (approximate with quarterly here). Higher frequency always earns at least as much at the same nominal rate.
When are contributions added?
At the end of each period (ordinary annuity). Beginning-of-period contributions would earn slightly more; this tool uses the end-of-period convention and notes it in the formula legend.
What happens with a 0% rate?
Growth is linear: principal plus contributions times periods. No interest is earned, and the effective rate is exactly 0%.
Does this include taxes or withdrawals?
No — v1 models pure growth only. Taxes, withdrawals, inflation and variable rates are follow-ups; treat results as before-tax, uninterrupted growth.