Compound Savings Calculator
Free compound savings calculator. See how your savings grow with compound interest and regular contributions over time with detailed growth charts.
Deposit Growth Calculator
Free deposit growth calculator. See how regular deposits grow over time in an interest-bearing account with a clear breakdown of contributions vs interest earned.
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$
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Final Balance After 20 Years
$128,714.64
0.40% from interest
Total Contributions⧉
$77,000.00
$5,000.00 initial + $300.00/mo × 240 months
Total Interest Earned⧉
$51,714.64
0.40% of final balance
Effective Multiplier⧉
1.67x
Balance / contributions
Contributions vs Interest
Contributions 60%
Interest 40%
Year-by-Year Growth
| Year | Balance | Contributions | Interest | Interest % |
|---|---|---|---|---|
| 1 | $8,904.89 | $8,600.00 | $304.89 | 3.4% |
| 2 | $12,989.16 | $12,200.00 | $789.16 | 6.1% |
| 3 | $17,261.07 | $15,800.00 | $1,461.07 | 8.5% |
| 4 | $21,729.22 | $19,400.00 | $2,329.22 | 10.7% |
| 5 | $26,402.64 | $23,000.00 | $3,402.64 | 12.9% |
| 6 | $31,290.76 | $26,600.00 | $4,690.76 | 15% |
| 7 | $36,403.44 | $30,200.00 | $6,203.44 | 17% |
| 8 | $41,751.00 | $33,800.00 | $7,951.00 | 19% |
| 9 | $47,344.22 | $37,400.00 | $9,944.22 | 21% |
| 10 | $53,194.39 | $41,000.00 | $12,194.39 | 22.9% |
| 11 | $59,313.31 | $44,600.00 | $14,713.31 | 24.8% |
| 12 | $65,713.34 | $48,200.00 | $17,513.34 | 26.7% |
| 13 | $72,407.39 | $51,800.00 | $20,607.39 | 28.5% |
| 14 | $79,408.96 | $55,400.00 | $24,008.96 | 30.2% |
| 15 | $86,732.18 | $59,000.00 | $27,732.18 | 32% |
| 16 | $94,391.82 | $62,600.00 | $31,791.82 | 33.7% |
| 17 | $102,403.35 | $66,200.00 | $36,203.35 | 35.4% |
| 18 | $110,782.93 | $69,800.00 | $40,982.93 | 37% |
| 19 | $119,547.47 | $73,400.00 | $46,147.47 | 38.6% |
| 20 | $128,714.64 | $77,000.00 | $51,714.64 | 40.2% |
Planning notes, formulas, and examples
About the Deposit Growth Calculator
The Deposit Growth Calculator models how regular deposits into an interest-bearing account grow over time. Enter an initial deposit, recurring monthly contribution, APY, and time horizon to see how your total balance builds — with a clear split between money you contributed and interest the account earned for you.
Understanding the contributions-vs-interest breakdown is one of the most powerful lessons in personal finance. In the early years, nearly all of your balance comes from contributions. But as the account grows, compounding takes over and interest becomes a larger percentage of each new dollar. This calculator makes that transition visible.
Use it for any interest-bearing deposit account: savings, money market, CDs, or even a brokerage cash sweep. Watching the split between your original deposits and the interest earned over time illustrates how compounding accelerates growth. This visual breakdown motivates consistent saving and helps you evaluate whether your current rate is competitive.
When This Page Helps
Seeing the split between your contributions and the interest your money earns is a powerful motivator. It shows you the concrete dollar value of compounding and helps you understand why starting early and contributing consistently matters more than chasing a slightly higher rate. Consistency in contributions often matters more than a fractional APY advantage.
How to Use the Inputs
- Enter an initial deposit amount (or 0 if starting from scratch).
- Enter the amount you plan to deposit each month.
- Enter the account APY.
- Enter the time horizon in years.
- View the total balance, total contributions, total interest, and the interest share percentage.
- Review the year-by-year table to see compounding accelerate over time.
Formula used
FV = P(1 + r/12)^(12t) + PMT × [((1 + r/12)^(12t) – 1) / (r/12)]
Total Contributions = P + PMT × 12 × t
Total Interest = FV – Total Contributions
Interest Share = Total Interest / FV × 100Example Calculation
Result: Final balance: $126,818 (contributions: $77,000, interest: $49,818)
Starting with $5,000 and depositing $300/month at 4.5% APY for 20 years: your total contributions are $77,000 ($5,000 initial + $300 × 240 months). The account earns $49,818 in compound interest, bringing the final balance to $126,818. Interest makes up 39% of the final balance — nearly $50,000 you never had to deposit.
Tips & Best Practices
- Even $50/month grows to meaningful amounts over 10–20 years thanks to compounding.
- Increasing your monthly deposit by just $25 can add thousands over a long horizon.
- The interest percentage grows dramatically after 10+ years — patience is key.
- Automate deposits on payday so contributions happen before discretionary spending.
- Higher APY matters most on large balances — focus on consistent deposits first.
- Use this calculator to model tax-refund or bonus deposits as one-time additions to your initial balance.
Contributions vs Interest: The Crossover
In the early years of saving, nearly all growth comes from your deposits. But there is a crossover point where annual interest earned exceeds annual contributions. For a $300/month saver at 4.5% APY, this crossover happens around year 12–15. After that, your money is working harder for you than you are working for it.
The Power of Consistency
The most important factor in deposit growth is not the rate — it is consistency. Missing even a few monthly deposits creates gaps in compounding that are hard to recover. Automated recurring deposits eliminate the temptation to skip a month and ensure your account grows steadily.
Using Deposit Growth for Goal Planning
Reverse the calculation to plan your savings strategy. If you need $100,000 in 15 years, this calculator shows you exactly what monthly deposit and APY combination gets you there. Adjust the inputs until the output matches your goal, then automate that deposit and let compounding handle the rest.
Sources & Methodology
Last updated:
Methodology
This worksheet applies deposit- and savings-instrument compounding using the stated APY, rate, term, and any early-withdrawal or maturity rules. It is a planning aid for comparing deposit-style products, not a quoted offer or guarantee.
Where the instrument has special rules (Treasury securities, I Bonds, CDs, or early-withdrawal penalties), the page keeps those rules explicit so the comparison stays conservative.
Sources
- Deposit accounts and CDs (FDIC) — Bank-deposit and certificate-of-deposit context.
- Savings Bonds and Treasury securities (U.S. TreasuryDirect) — Official savings-bond, I Bond, and Treasury bill rules.
- Money market funds (U.S. Securities and Exchange Commission) — Context for money-market return comparison.
Frequently Asked Questions
Compounding means you earn interest on previously earned interest, not just on your deposits. Early on, interest is small because the balance is small. Over time, the interest snowball grows larger. After 20 years, compounding can contribute 30–50% of your total balance, depending on the rate.
Monthly deposits slightly outperform lump-sum annual deposits of the same yearly total because money is invested sooner on average. However, the difference is small. Consistency matters more than timing — the best deposit schedule is one you can maintain reliably.
Use the current APY of your account for short-term projections (1–3 years). For longer projections, consider using a conservative estimate (e.g., 3–4%) to account for potential rate changes. Historical average savings rates have ranged from 0.5% to 5%, depending on the rate environment.
Yes, for a single CD with no additional deposits. Set the monthly contribution to $0 and enter the initial deposit and CD APY. For CD ladders or multiple CDs, use the dedicated CD Ladder Calculator for a more detailed analysis.
It depends on the time horizon and rate. At 4% APY over 10 years, interest might be 15–20% of the balance. Over 30 years, it could be 40–50%. The longer you save, the more compounding contributes. This is the core argument for starting to save as early as possible.
Both help, but higher monthly contributions typically have more impact over the long run because they add fresh capital every month. A $10,000 initial deposit with $200/month contributions usually beats a $20,000 initial with $100/month contributions over 15–20 years.
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