Tools
Compound interest / APY calculator
See how a starting balance and regular contributions could grow over time. Compare a nominal interest rate, an APY, or a hypothetical annual return, with your deposit schedule made explicit. An educational illustration — not a forecast or recommendation.
Calculated results
- Ending balance
- $31,998.32
- Starting principal
- $10,000.00
- Added contributions
- $12,000.00
- Interest growth
- $9,998.32
120 scheduled contributions · Effective annual yield: 5.1162%.
Balance over time
Lines connect year-end and final snapshots; the table gives each amount.
Yearly progression and exact amounts
Year-end values are before the next beginning-of-period contribution. A final partial-year row is included.
| Period | Added contributions | Growth / loss | Balance |
|---|---|---|---|
| Start | $0.00 | $0.00 | $10,000.00 |
| Year 1 | $1,200.00 | $539.50 | $11,739.50 |
| Year 2 | $2,400.00 | $1,168.01 | $13,568.01 |
| Year 3 | $3,600.00 | $1,890.06 | $15,490.06 |
| Year 4 | $4,800.00 | $2,710.44 | $17,510.44 |
| Year 5 | $6,000.00 | $3,634.20 | $19,634.20 |
| Year 6 | $7,200.00 | $4,666.60 | $21,866.60 |
| Year 7 | $8,400.00 | $5,813.23 | $24,213.23 |
| Year 8 | $9,600.00 | $7,079.91 | $26,679.91 |
| Year 9 | $10,800.00 | $8,472.79 | $29,272.79 |
| Year 10 | $12,000.00 | $9,998.32 | $31,998.32 |
Assumptions
A rate before compounding. The selected compounding frequency determines its effective annual yield.
- Rates stay constant throughout the illustration. Interest and gains remain invested; taxes, fees, inflation and withdrawals are excluded.
- Months are equal fractions of a year. Daily schedules use 365 equal periods per year, without actual calendar dates or leap-day adjustments.
- Contributions occur at the selected frequency. Beginning means a full deposit at the start of each contribution period; end means at its completion. No partial end deposit is assumed. A zero-length horizon has no deposits.
- For unmatched schedules and partial periods, growth accrues exponentially over fractions of a compounding period. This is an educational interpolation, not a bank’s contractual interest-crediting method.
- Year-end rows are before the next beginning-of-period contribution, and include the contribution ending that year. The final row includes any partial year.
- Calculations retain full precision; displayed currency rounds to cents. Displayed growth is the difference between the displayed balance, principal and added contributions.
Learn more: What is APY? and the Saving and Cash guide.
Primary references: Investor.gov compound interest calculator, Small Savings Add Up to Big Money, and CFPB Regulation DD Appendix A.
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