$300/month + $1,000 initial at 7.0% annual return, compounded monthly.
Contributions vs Interest
How your future value is built.
Year-by-Year Growth
Balance vs total contributions over time.
Year-by-Year Breakdown
Balance, invested, and interest earned per year.
| Year | Balance | Total Invested | Interest Earned |
|---|---|---|---|
| 1 | $4,790 | $4,600 | $190 |
| 2 | $8,854 | $8,200 | $654 |
| 3 | $13,212 | $11,800 | $1,412 |
| 4 | $17,885 | $15,400 | $2,485 |
| 5 | $22,895 | $19,000 | $3,895 |
| 6 | $28,268 | $22,600 | $5,668 |
| 7 | $34,030 | $26,200 | $7,830 |
| 8 | $40,207 | $29,800 | $10,407 |
| 9 | $46,832 | $33,400 | $13,432 |
| 10 | $53,935 | $37,000 | $16,935 |
| 11 | $61,552 | $40,600 | $20,952 |
| 12 | $69,719 | $44,200 | $25,519 |
| 13 | $78,477 | $47,800 | $30,677 |
| 14 | $87,868 | $51,400 | $36,468 |
| 15 | $97,938 | $55,000 | $42,938 |
| 16 | $108,735 | $58,600 | $50,135 |
| 17 | $120,314 | $62,200 | $58,114 |
| 18 | $132,729 | $65,800 | $66,929 |
| 19 | $146,042 | $69,400 | $76,642 |
| 20 | $160,317 | $73,000 | $87,317 |
Monthly Investment Calculator — See Your Habit Become Wealth
About this tool
Free Monthly Investment Calculator — Multi-Currency, Any Frequency
This monthly investment calculator shows how any recurring contribution — daily, weekly, bi-weekly, monthly, quarterly, or annual — grows into significant wealth through compound interest. Enter your contribution amount, initial investment, expected annual return, and how many years you plan to invest. The calculator shows your projected future value, total contributions, total interest earned, return on investment, and a wealth multiple — all updated instantly as you adjust the sliders.
Unlike most investment calculators that assume a fixed monthly contribution, this tool lets you choose any contribution frequency. If you invest $100 every week, enter weekly and $100 — the calculator converts it to the monthly equivalent automatically and shows the precise impact. This is useful for investors who receive bi-weekly paychecks and want to automate contributions on payday, or for daily savers who want to model small consistent habits over decades.
The Compare mode is one of the most powerful features. Toggle it on and set a second contribution amount — both scenarios plot on the same chart simultaneously. The gap between the two growth lines shows exactly how much extra wealth is created by increasing contributions. Comparing $300/month to $600/month at 7% over 20 years reveals a gap of roughly $130,000 — more than the extra $72,000 invested, because the additional money also compounds. This makes it easy to answer "what would happen if I increased my contribution by just $100/month?"
The calculator supports six currencies: USD, EUR, GBP, CAD, AUD, and INR. Switch currencies from the header dropdown. Each uses proper locale formatting — EUR uses European number separators, INR uses lakh and crore abbreviations for large balances. This makes the tool useful for investors in the US, UK, Europe, Canada, Australia, and India without needing a separate tool for each currency.
Milestone markers appear on the growth chart when your projected balance first crosses meaningful thresholds — $10K, $50K, $100K, $500K, $1M, and beyond. These make it visually clear how many years it takes to reach each financial milestone, which is motivating for long-term savers. The Rule of 72 estimate in the sidebar provides instant mental math: at 7%, your money doubles every ~10 years. All calculations run in your browser. No financial data is uploaded. Use this tool alongside the Compound Interest Calculator, SIP Calculator, or Mortgage Calculator for broader financial planning.
Features
- Any contribution frequency: daily, weekly, bi-weekly, monthly, quarterly, or annually
- Multi-currency support: USD, EUR, GBP, CAD, AUD, INR with proper locale formatting
- Compare mode — plot two contribution amounts on the same chart simultaneously
- Milestone markers on chart when balance crosses $10K, $100K, $1M, etc.
- Rule of 72 live doubling-time estimate based on current rate
- Rate presets: 401(k) avg (7%), S&P 500 (10%), Roth IRA (8%), HYSA 2025 (4.5%)
- Initial investment plus recurring contributions modeled together
- Stacked bar showing contributions vs interest in final balance
- Interactive year-by-year chart with hover tooltip
- Year-by-year table with balance, invested, and interest earned per year
- Download full projection as CSV for spreadsheet analysis
- Runs entirely in browser — no account, no upload, no data tracking
How to Use This Investment Calculator
- 1Choose your contribution frequencySelect how often you invest: daily, weekly, bi-weekly, monthly, quarterly, or annually. Most people invest monthly, but if you prefer to invest on payday (bi-weekly), select that option. The calculator adjusts all math automatically for whichever frequency you choose.
- 2Set your contribution amountEnter the amount per period. If you chose weekly, enter your weekly investment amount. The sidebar shows the monthly equivalent so you can compare across frequencies. Use the slider for quick adjustments or type directly into the number field for precision.
- 3Add your initial investmentEnter any money you are starting with today. This could be existing savings, a windfall, a bonus, or an opening deposit. The calculator compounds this amount immediately alongside ongoing contributions from the start.
- 4Select annual return and durationUse the presets for common benchmarks — S&P 500 (10%), 401(k) average (7%), Roth IRA (8%), or HYSA (4.5%) — or type any custom rate. Set the number of years you plan to keep investing. Notice how extending from 10 to 20 years often more than doubles the final balance due to late-stage compounding.
- 5Toggle Compare mode to see two scenariosTurn on Compare mode and set a second contribution amount. Both growth trajectories appear on the chart simultaneously. The tooltip shows both balances for any year. This is the fastest way to answer "what if I invested an extra $100 per month?" without running two separate calculations.
- 6Read the milestone markers and Rule of 72The chart shows vertical milestone lines when your balance first crosses key thresholds. The Rule of 72 in the sidebar tells you how fast your money doubles at the current rate. Together these give a quick intuitive picture of the timeline to your financial goals.
- 7Download or copy your projectionUse the Download CSV button to export the year-by-year table for deeper analysis in Excel or Google Sheets. Use Copy summary to grab key figures for notes, financial planning, or sharing with an advisor or accountability partner.
Common Use Cases
Frequently Asked Questions
A monthly investment calculator computes how recurring contributions grow with compound interest over time. Each contribution is added to the running balance and the entire balance earns interest every compounding period. Because each dollar invested earlier has more time to compound, consistent investing habits produce exponential growth over long periods even with modest contribution amounts.
The frequency affects how quickly money enters the account and begins compounding. Daily investing means contributions start earning sooner. However, the mathematical difference between daily and monthly is small for most rates and time horizons. What matters far more is the total annual contribution amount and how long you stay invested. This calculator converts any frequency to a monthly equivalent so you can compare apples to apples.
At 7% annual return (a common long-term estimate for a diversified stock portfolio), investing $500 per month for 20 years produces approximately $260,000. Total contributions would be $120,000 — meaning around $140,000 would come from compound growth. At 10%, the same contributions could reach around $380,000. Use the calculator to model your exact scenario.
Common benchmark rates: S&P 500 historical average ~10%, diversified 401(k) or IRA portfolio 6–8%, conservative bonds 3–5%, high-yield savings accounts in 2025 roughly 4–4.5%. The calculator includes preset buttons for these common scenarios. These are historical averages — actual future returns are not guaranteed and can vary significantly by year and market conditions.
Compare mode lets you plot two different contribution amounts on the same chart simultaneously. For example, you can see what happens if you invest $300/month versus $600/month over 20 years, with the gap between the two lines showing the compounding benefit of the extra contribution. The tooltip and projection table both show both scenarios for side-by-side comparison.
Milestone markers are vertical reference lines that appear on the growth chart when your projected balance first crosses a round number — for example $10,000, $50,000, $100,000, $250,000, or $1,000,000 (scaled for each currency). They make it easy to see at a glance how many years it takes to reach each significant threshold, which is motivating for long-term savers and investors.
The calculator supports USD (US Dollar), EUR (Euro), GBP (British Pound), CAD (Canadian Dollar), AUD (Australian Dollar), and INR (Indian Rupee). Switch currencies using the dropdown in the header. The formatting uses locale-appropriate number formats — for example, INR uses lakh/crore abbreviations for large numbers.
The Rule of 72 is a mental math shortcut: divide 72 by your annual return rate to estimate how many years it takes for your investment to double. At 7%, money doubles in about 10.3 years. At 10%, about 7.2 years. At 4%, about 18 years. The calculator shows this estimate live as you adjust the rate slider.
Yes, fully private. All calculations run in your browser using JavaScript. Your contribution amount, rate, duration, currency, and any comparison scenarios are never sent to a server. Inputs are saved in your browser's localStorage so your settings persist across sessions. Use the Reset button to clear saved settings at any time.