Kids Investment Calculator: What Could Your Child's Account Grow To?
Enter a starting amount, a monthly contribution and your child's age to see what the account could grow to, and what waiting costs.
Key takeaways
- At a hypothetical 6% return, $50 a month from birth is $10,800 of deposits and grows to about $19,368 by 18.
- Starting five years later costs more than the skipped deposits: $1,000 plus $50 a month from birth reaches about $22,304 at 18, versus about $13,950 starting at age 5.
- The calculator ignores taxes, fees and inflation, and the account type decides how much of the growth your child keeps.
Enter what's in the account today, what you can add each month, and your child's age. The calculator shows what it could grow to at the return you pick, and how much of that is growth rather than your own deposits.
18 years of growth. Start the same plan five years later and it reaches about $13,950 at 18, on $8,800 put in.
Illustration only. Assumes the return you picked, every year, compounded monthly, with deposits at the end of each month. Real returns vary year to year and can be negative. No taxes, fees or inflation are included. Not a prediction or a recommendation.
What $25 to $250 a month looks like at 18
These start at birth with nothing in the account and run to the 18th birthday, compounded monthly. The returns are hypothetical. No account is promised any of them.
| Each month | You put in | At 4% | At 6% | At 8% |
|---|---|---|---|---|
| $25 | $5,400 | $7,890 | $9,684 | $12,002 |
| $50 | $10,800 | $15,780 | $19,368 | $24,004 |
| $100 | $21,600 | $31,559 | $38,735 | $48,009 |
| $250 | $54,000 | $78,898 | $96,838 | $120,022 |
Why the start date matters more than the amount
Take $1,000 at birth plus $50 a month at a hypothetical 6%. At 18 that's about $22,304, on $11,800 of deposits.
Start the same plan at age 5 instead and it reaches about $13,950 at 18, on $8,800 of deposits. Waiting five years saved $3,000 in contributions and cost roughly $8,350 at the finish line. That gap is compound interest at work: early dollars earn growth, and then the growth earns growth.
Which return should you pick?
Nobody knows what the next 18 years will return, so treat the rate as a dial you can turn. Run the calculator at 4% and again at 8% and you'll see a realistic range instead of one comforting number.
- Savings accounts pay interest that moves with the rates banks offer. See savings accounts for kids. Over long stretches that has usually been well below what stock funds earned.
- Broad stock funds have historically grown more over long periods, with sharp drops along the way. See what an index fund is for why many kids' accounts start there.
- Bonds usually land in between, with smaller swings. The trade-off is covered in stocks vs. bonds.
The account changes the real number
The calculator ignores taxes. The account you use decides how much of the growth your child keeps.
- UTMA or UGMA custodial account: growth is the child's income and can be taxed each year under the kiddie tax.
- 529 plan: growth is tax-free when it's spent on qualified education. See 529 plans explained.
- Custodial Roth IRA: growth can come out tax-free in retirement, but your child needs earned income to contribute. See the custodial Roth IRA rules.
- Trump Account: a federal account for kids with its own contribution cap and tax rules. See Trump Accounts.
What happens if the money keeps growing after 18
The $50-a-month plan from birth reaches about $19,368 at 18 at 6%. If no one adds another dollar and it keeps earning the same hypothetical 6%, it's about $322,653 at 65. That long tail is the idea behind Coast FIRE for kids. Set the calculator's target to 65 to try your own numbers.
Where MemoryBank fits
This page works from numbers you type in. MemoryBank connects the accounts you've already opened and shows your child their real balance, with a projection of what it could grow to in 1, 5, 10, 25 and 50 years. It uses the same kind of math, applied to the money your kid actually has.
Figures on this page are illustrations at hypothetical returns, not predictions. Real returns vary and can be negative, and taxes, fees and inflation reduce what you keep. MemoryBank is an education and display tool, not a financial or tax advisor. For choices about accounts or investments, talk with a financial professional.
Frequently asked questions
How much will my child's investment be worth at 18?
It depends on how much goes in, when it starts, and what it earns. As a hypothetical example, $50 a month from birth is $10,800 of deposits and grows to about $15,780 at 4%, $19,368 at 6%, or $24,004 at 8% by 18. Real returns vary year to year.
How much should I invest for my child each month?
There's no right number; it's whatever fits your budget consistently. What matters more is starting early, because the first years of contributions have the longest time to compound. Even $25 a month from birth is $5,400 of deposits and about $9,684 at 18 at a hypothetical 6%.
What rate of return should I use in a kids investment calculator?
No one can know the rate in advance. Running the numbers at a low and a high hypothetical rate, such as 4% and 8%, shows how wide the outcomes can be. Savings accounts usually earn less than stock funds over long periods, and stock funds swing more along the way.
Does this calculator include taxes and inflation?
No. It shows growth before taxes, fees and inflation. The account type changes what your child keeps: growth in a 529 spent on education or in a qualified custodial Roth IRA withdrawal is tax-free, while a UTMA's earnings can be taxed each year under the kiddie tax.
Is a lump sum better than investing monthly for a child?
Money invested earlier has more time to compound, so a lump sum at birth grows more than the same total spread out over years. For example, $5,000 at birth is about $14,684 at 18 at a hypothetical 6%. Most families add money over time because that's how their budget works, and a steady habit gets them most of the way.
Can MemoryBank project my child's real account?
Yes. MemoryBank connects the accounts you've already opened and shows your child their actual balance with a projection of what it could grow to in 1, 5, 10, 25 and 50 years. It's a display and teaching tool; it doesn't hold or move money.
What to do next
- Run the calculator twice, at 4% and at 8%, to see your range.
- Check which account fits the goal with how to start investing for your child.
- Find a monthly amount that fits with how to plan a family budget, then automate it at your brokerage or plan.
Written by Josh Ackerman
Founder of MemoryBank. A computer scientist and M.B.A. with 20+ years of investing and technology experience, Josh built the first MemoryBank in his basement so his three kids could watch their own accounts grow. More about Josh →
See it in one place
MemoryBank shows your kid's UTMA, 529, Roth IRA, brokerage, and savings in one place — across every institution — and explains their accounts and how investing works in age-appropriate terms they actually understand. It runs in any browser and as an app on iPhone and Android.
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Coast FIRE for Kids: Could You Set Your Child Up to Never Worry About Money?
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MemoryBank is a display and education tool, not a financial advisor. Nothing here is investment, tax, or legal advice. Verify program details with the IRS, your tax advisor, or a licensed financial professional before making decisions.