Your plan
Wealth curve - balance vs what you put in
The gap between the lines is compounding - $176,649 you never had to earn.
Your wealth growth plan
Your compounding trajectory
Starting with $5,000 and adding $300/month at 7.0% annual growth, you'd reach $271,649 in 25 years.
• You contribute $95,000; compounding contributes $176,649. That's 2.86× your money.
The cost of waiting 10 years
The identical plan started 10 years later ends at $109,333 - waiting costs $162,315. Time in the market is the input you can't buy back.
How to actually capture this
• Automate the monthly contribution on payday - compounding only works on money that actually arrives every month.
• Raise the contribution with every raise: +10% of each pay bump is invisible to your lifestyle and enormous at the horizon.
• Guard the rate: high-fee funds quietly eat the growth - see our Investment Fee Drag calculator for what a 1% expense ratio does to this exact projection.
• This is a fixed-rate illustration; real markets vary year to year. The long-run average is what compounds - stay in through the noise.
How the compound interest calculator works
The projection compounds monthly: each month your balance grows by the annual return divided by 12, then your contribution is added. Over decades this produces the famous hockey-stick curve - not because anything changes, but because growth starts earning growth. The chart splits your ending balance into what you contributed and what compounding added, which is the clearest way to see the machine working.
The most valuable number here is the cost of waiting. The same plan started ten years later doesn't end 25% smaller - it can end 50% or more smaller, because the years you cut are the steep end of the curve. Time in the market is the one input you cannot buy back, which is why the standard advice is to start with whatever amount you can automate today rather than waiting until you can invest 'properly'.
It's also worth separating the two ways this projection can grow: a larger starting balance and a larger monthly contribution compound differently. The starting balance has the most time to grow, so it's most sensitive to the return rate; the contribution stream adds new principal every month, so it's more sensitive to consistency than to any single year's return. Neither substitutes for the other - the chart's split between contributed and grown dollars shows exactly how much each is doing.
Frequently asked questions
- What annual return should I assume?
- Long-run averages for diversified stock portfolios have historically been in the 7-10% range before inflation, but nothing is guaranteed. Run the projection at 5%, 7%, and 9% to see a realistic range instead of a single guess.
- Is this projection guaranteed?
- No - it's a fixed-rate illustration. Real markets swing year to year; the long-run average is what compounds. The lesson that survives the noise: contributions plus time dominate the outcome.
- How often does compounding happen?
- This calculator compounds monthly, matching how most investment growth and contribution schedules work in practice. The difference between monthly and daily compounding at these rates is negligible.
- What matters more: the starting amount or the monthly contribution?
- Over long horizons, the monthly contribution usually dominates. A modest start with a consistent automated contribution beats a large lump sum with nothing added - drag the sliders and watch which one moves the ending balance more.
- Should I account for taxes in this projection?
- This model shows pre-tax growth, matching how most people think about their investment goal. In a taxable account, dividends and realized gains create tax drag along the way; in a 401(k), IRA, or Roth account, growth is tax-deferred or tax-free, so the projection here is closest to reality for tax-advantaged accounts.