Three scenarios
Growth over time
Yearly breakdown
| Year | Contributed | Interest this year | Balance | Real value |
|---|---|---|---|---|
| 1 | $16,000.00 | $518.65 | $16,518.65 | $16,037.52 |
| 2 | $22,000.00 | $784.23 | $23,302.87 | $21,965.19 |
| 3 | $28,000.00 | $1,060.63 | $30,363.50 | $27,786.90 |
| 4 | $34,000.00 | $1,348.29 | $37,711.79 | $33,506.43 |
| 5 | $40,000.00 | $1,647.67 | $45,359.46 | $39,127.46 |
| 6 | $46,000.00 | $1,959.25 | $53,318.70 | $44,653.57 |
| 7 | $52,000.00 | $2,283.52 | $61,602.22 | $50,088.24 |
| 8 | $58,000.00 | $2,621.00 | $70,223.22 | $55,434.86 |
| 9 | $64,000.00 | $2,972.23 | $79,195.45 | $60,696.72 |
| 10 | $70,000.00 | $3,337.78 | $88,533.23 | $65,877.04 |
| 11 | $76,000.00 | $3,718.21 | $98,251.44 | $70,978.93 |
| 12 | $82,000.00 | $4,114.15 | $108,365.59 | $76,005.44 |
| 13 | $88,000.00 | $4,526.21 | $118,891.80 | $80,959.53 |
| 14 | $94,000.00 | $4,955.07 | $129,846.87 | $85,844.08 |
| 15 | $100,000.00 | $5,401.39 | $141,248.26 | $90,661.88 |
| 16 | $106,000.00 | $5,865.90 | $153,114.16 | $95,415.68 |
| 17 | $112,000.00 | $6,349.34 | $165,463.50 | $100,108.14 |
| 18 | $118,000.00 | $6,852.47 | $178,315.97 | $104,741.84 |
| 19 | $124,000.00 | $7,376.10 | $191,692.07 | $109,319.31 |
| 20 | $130,000.00 | $7,921.06 | $205,613.13 | $113,843.01 |
| 21 | $136,000.00 | $8,488.23 | $220,101.36 | $118,315.33 |
| 22 | $142,000.00 | $9,078.50 | $235,179.86 | $122,738.61 |
| 23 | $148,000.00 | $9,692.82 | $250,872.68 | $127,115.12 |
| 24 | $154,000.00 | $10,332.17 | $267,204.86 | $131,447.08 |
| 25 | $160,000.00 | $10,997.57 | $284,202.43 | $135,736.66 |
| 26 | $166,000.00 | $11,690.08 | $301,892.50 | $139,985.96 |
| 27 | $172,000.00 | $12,410.80 | $320,303.30 | $144,197.04 |
| 28 | $178,000.00 | $13,160.88 | $339,464.18 | $148,371.90 |
| 29 | $184,000.00 | $13,941.53 | $359,405.71 | $152,512.50 |
| 30 | $190,000.00 | $14,753.97 | $380,159.68 | $156,620.76 |
What is the Compound Interest Calculator?
A compound interest calculator shows how money grows when interest earns interest. Plug in a principal, an annual rate, a contribution schedule, and a time horizon. The calculator returns the nominal balance year by year, the inflation-adjusted real value, and a chart that overlays the contribution-vs-growth split so you can see exactly when interest takes over from saving.
This calculator runs three scenarios at once (default conservative 4%, balanced 7%, aggressive 10%) so you can compare investment strategies side by side. It accounts for inflation, contribution growth from raises, and four compounding frequencies. Everything runs in your browser, no signup, no quota.
How it works
Features
Why this calculator
Most calculators run one. NerdWallet, Investor.gov, BankRate all show a single line. We show three so you can pick by comparing, not by guessing.
Most free calculators show the nominal number only. A $1M projection at 30 years feels great until you realize 3% inflation cuts it to $412K of buying power. We show both.
No affiliate links to brokerages or robo-advisors. We don't earn anything by pushing you to a higher-risk option. The math is the math.
Investor.gov lets you save scenarios but ties them to an account. We let you tune and re-tune freely with no friction.
Who uses it
Real use cases
- You're 28 and wondering if maxing out a Roth IRA at $7000 a year really matters. Set principal $0, contribution $583/month, 7% rate, 37 years. That's 2.4M nominal. Switch on inflation: 1M in today's dollars. Now do it again starting at 38. The 10-year delay costs you $400K.
- You got a 3% raise and want to grow your savings rate with it. Plug 2% contribution growth in scenario A, 0% in scenario B. The chart shows the gap is much bigger than 2% sounds.
- Your bank offers 4.5% APY on a HYSA, your brokerage averages 9% historically. Side by side: $50K principal, $0 contributions, 30 years. The HYSA is $185K, the index fund is $663K. Risk vs return in one chart.
- You're explaining compounding to a junior. Set principal $1, contribution $0, 8% rate, 50 years. Result: $46.90. Now tell them to imagine that's a single dollar. Compounding is exponential.
- Your kid's college fund needs $200K in 18 years. Scenario A: 5% in a 529 plan. Scenario B: 7% in a balanced index. Compare contribution required to hit the target.
- You and a friend are arguing about whether to pay off a 6% mortgage faster or invest the cash at a hoped-for 8%. Run both scenarios for the remaining mortgage term. The real-return view changes the answer when inflation is high.
Compared with other compound interest calculators
| Feature | Molixa | NerdWallet | Investor.gov | BankRate |
|---|---|---|---|---|
| Multiple scenarios side by side | 3 at once | 1 | 1 | 1 |
| Inflation-adjusted real return | Yes, toggle | No | Partial | No |
| Contribution growth modeling | Yes | No | No | No |
| 4 compounding frequencies | Yes | Yes | Yes | Yes |
| Milestone markers on chart | 5/10/20/30/40/50 | Annual only | Annual only | Annual only |
| Contribution vs growth shading | Yes | No | No | No |
| Affiliate links / push to product | None | Many | None | Many |
| No signup | Yes | Yes | Yes | Yes |
Frequently asked questions
Is the compound interest calculator free?▾
Yes. Unlimited use, no signup, no daily cap. All math runs in your browser. NerdWallet's calculator is free but limited to one scenario at a time and pushes you toward affiliate products; ours runs three scenarios side by side and recommends nothing.
What is compound interest?▾
Interest you earn on both the original deposit and the interest already added to it. After year 1, you earn interest on a slightly bigger pile. After year 2, an even bigger pile. Over decades the curve gets steep. That is the engine behind every retirement account.
How do you calculate compound interest?▾
The formula is A = P(1 + r/n)^(nt) where P is principal, r is annual rate, n is compounding periods per year, t is years. We compound daily, monthly, quarterly, or yearly per your choice, layer in periodic contributions, and round to whole cents at year ends.
Can I compare multiple scenarios?▾
Yes. The tool runs three scenarios in parallel: a conservative 4%, a balanced 7%, and an aggressive 10% are the defaults. You can rename, retune, or zero-out any of them. The chart overlays all three for visual comparison.
What is real return after inflation?▾
Your nominal balance is the dollar number on the screen. Real balance subtracts inflation, showing how much that money will actually buy in today's purchasing power. A $1M nest egg in 30 years at 3% inflation is only worth ~$412K in today's dollars.
What inflation rate should I use?▾
Default 3% is the long-term US average. Plug in 2% for a more optimistic view, 4-5% for a conservative one. Recent years (2021-2023) saw 5-9% inflation, but that is unusual; 3% is a reasonable long-horizon default.
What contribution frequencies are supported?▾
Weekly, biweekly (matches most paychecks), monthly, annual, or none. The math compounds contributions per their period, so a $500 monthly contribution grows slightly differently than a $6000 annual contribution at the same rate.
Can I model contribution increases?▾
Yes. Set 'contribution growth' to 2% to grow your contribution by 2% each year (matching a typical raise). Most retirement calculators only model flat contributions, which understates what you'll actually save.
What's the difference between APR and APY?▾
APR is the simple annual rate. APY (annual percentage yield) accounts for compounding within the year. A 5% APR compounded monthly equals about 5.12% APY. We label our input as the annual rate and apply your chosen compounding frequency on top.
Is my data sent anywhere?▾
No. The form, the math, the chart, all run in your browser. Your principal, your rates, your savings goals stay on your laptop. We don't even know you ran the calculator.
See your money grow
Three scenarios, inflation-adjusted, milestone markers, free unlimited. No signup, no affiliate steering.
Open the compound interest calculatorThe Compound Interest Calculator page is built, reviewed, and maintained by the Molixa team. We use the tool we ship and update the docs when the behavior changes.
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