Savings & Investment Growth Calculator

See how your savings and investments grow over time with compound interest. Visualize the power of regular contributions, track milestones, and find when your money starts working harder than you do.

1%15%
1 yr50 yrs

Growth Summary

Final Balance
$854,537
Total Contributions
$190,000
Total Earnings
$664,537
Earnings % of Total
77.8%

Milestones

Reach $100K
Year 10
Reach $250K
Year 17
Reach $500K
Year 24
Earnings > Contributions
Year 8

78% of your final balance came from compound growth — your money earning money.

Year 8: Your money earns more than you contribute.

Growth Over Time

Year 8: Your money earns more than you contribute

See your complete financial picture

With $500/month invested, you could reach $854,537 in 30 years. See how this fits into your full financial plan with taxes, expenses, and more.

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The Power of Compound Interest

Albert Einstein reportedly called compound interest "the eighth wonder of the world." Whether or not he actually said it, the math behind it is genuinely remarkable. Here's a concrete example: if you invest $500 per month at an 8% annual return for 30 years, you'll end up with approximately $745,000. But here's the astonishing part — only $180,000 of that came from your own contributions. The remaining $565,000 was generated entirely by compound growth.

This happens because of the Rule of 72: divide 72 by your annual return rate to estimate how many years it takes to double your money. At 8%, your money doubles roughly every 9 years. After 9 years, your $1 becomes $2. After 18 years, it's $4. After 27 years, it's $8. Each doubling happens on a bigger base, which is why the growth curve accelerates dramatically in later years.

Your Contributions$180,000
Compound Growth$565,000

How to Start Investing with Any Amount

You don't need a large sum to begin building wealth. The most important step is to start — even with small amounts — and let time do the heavy lifting. Here's a practical order of operations:

1

Capture your employer's 401(k) match.

If your employer matches contributions (commonly 3-6% of salary), contribute at least enough to get the full match. This is an instant 50-100% return on your money.

2

Fund a Roth IRA.

After maxing the employer match, consider a Roth IRA (up to $7,000/year in 2025). Your contributions grow tax-free, and withdrawals in retirement are tax-free too.

3

Open a taxable brokerage account.

Once you've maxed tax-advantaged accounts, a standard brokerage account lets you invest with no contribution limits and full flexibility.

Even $100/month matters. At 8% annual returns, that becomes over $150,000 in 30 years. The key is consistency and time in the market.

Investment Accounts: 401(k) vs IRA vs Brokerage

Each account type offers different tax advantages:

Traditional 401(k)

Contributions reduce taxable income today. You pay taxes on withdrawals in retirement. Employer match is a major benefit. 2025 limit: $23,500 ($31,000 if 50+).

Roth IRA

Contributions are after-tax, but all growth and withdrawals are tax-free in retirement. Best if you expect a higher tax bracket later. 2025 limit: $7,000 ($8,000 if 50+).

Taxable Brokerage

No tax benefits on contributions, but no contribution limits or early withdrawal penalties. Long-term capital gains taxed at favorable rates (0%, 15%, or 20%). Most flexible option.

How to Choose Your Monthly Contribution Amount

Use the 50/30/20 rule as a starting framework: 50% of after-tax income for needs (housing, food, transportation), 30% for wants (dining out, entertainment, subscriptions), and 20% for savings and debt repayment. If 20% feels out of reach right now, start with whatever you can and increase it over time.

Set up automatic transfers to your investment accounts on payday, before you have a chance to spend the money. Treat investing like a bill that must be paid. Increase your contribution by 1% every six months, and direct any raises, bonuses, or windfalls toward investments.

See How Your Investments Fit Into Your Full Financial Plan

This calculator shows investment growth in isolation. Trajectoryy's full simulator shows how your investments interact with your income, taxes, expenses, loans, and retirement accounts — giving you a complete picture of your financial future.

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Frequently Asked Questions

What is compound interest and how does it work?
Compound interest is interest earned on both your original principal and on previously accumulated interest. Instead of earning a flat amount each year, your earnings grow exponentially because each year's returns are calculated on a larger base. Over long periods, this snowball effect is what turns modest monthly contributions into substantial wealth.
What is the Rule of 72?
The Rule of 72 is a quick way to estimate how long it takes to double your money. Divide 72 by your annual return rate. At 8% returns, your money doubles roughly every 9 years (72 / 8 = 9). At 10%, it doubles every 7.2 years. This rule highlights why even small differences in return rates matter enormously over decades.
What annual return rate should I use?
The S&P 500 has historically returned about 10% annually before inflation, or roughly 7% after inflation. A balanced portfolio of stocks and bonds might return 6-8%. Conservative investments like bonds or CDs typically return 3-5%. Use 7-8% for a diversified stock portfolio as a reasonable long-term estimate.
How does inflation affect my investment returns?
Inflation erodes purchasing power over time. If your investments grow at 8% but inflation is 3%, your real (inflation-adjusted) return is approximately 5%. A million dollars in 30 years will only buy about $412,000 worth of today's goods. Toggle the inflation adjustment in our calculator to see the difference.
Should I invest a lump sum or dollar-cost average?
Historically, lump-sum investing outperforms dollar-cost averaging about two-thirds of the time because markets tend to go up. However, dollar-cost averaging (investing a fixed amount monthly) reduces the risk of investing everything at a market peak and is psychologically easier. For most people with regular paychecks, automatic monthly contributions are the practical choice.
When does my money start earning more than I contribute?
The crossover point — when your annual investment earnings exceed your annual contributions — depends on your balance, return rate, and contribution amount. With $500/month at 8%, this typically happens around year 12-15. After this point, compound growth does more of the heavy lifting than your paycheck. Our calculator shows you this exact crossover year.
How much should I be saving and investing each month?
A common guideline is the 50/30/20 rule: 50% of after-tax income for needs, 30% for wants, and 20% for savings and investments. At minimum, contribute enough to get your employer's full 401(k) match — that's free money. Then build from there. Even $100/month invested at 8% grows to over $150,000 in 30 years.

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