Kids Savings Account Growth Calculator: What Saving for a Child Builds
Work out what a child's savings account grows to from a starting amount plus regular monthly contributions — and see how powerful starting early and letting time compound can be for a young child.
Adjust the inputs and select Calculate for a full breakdown.
Year-by-year growth schedule
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | Future value | Total contributions | Total interest earned |
|---|---|---|---|
| $500 + $50/mo · 5% · 18yr | $18,687.61 | $11,300.00 | $7,387.61 |
| $0 + $100/mo · 7% · 18yr (invested) | $43,072.10 | $21,600.00 | $21,472.10 |
| $1,000 + $25/mo · 4% · 18yr (cash) | $9,941.79 | $6,400.00 | $3,541.79 |
| $2,000 + $0/mo · 6% · 18yr (lump only) | $5,873.53 | $2,000.00 | $3,873.53 |
How This Calculator Works
Enter the starting amount, how much you'll add each month, the return you expect, and the years until the child needs the money. The calculator compounds the balance monthly and shows the ending value and how much is growth versus your contributions.
The Formula
Future Value with Regular Contributions
P = starting amount, PMT = monthly contribution, r = monthly rate (annual ÷ 12), n = number of months
Worked Example
Starting with $500 and adding $50 a month for 18 years at 5% grows to about $18,688 — of which roughly $7,388 is growth and the rest contributions. The long horizon is the magic: starting at birth gives nearly two decades for compounding, so even modest monthly amounts become a meaningful head start for college, a first car, or early adulthood. The same plan started at age 10 would grow far less, because the money has fewer years to compound.
Key Insight
Saving for a child is where compounding and time horizon do their most dramatic work, but the account choice matters and shapes the result. The options trade off control, taxes, and purpose: a basic kids' savings account or CD is simple and safe but low-return; a custodial account (UGMA/UTMA) can be invested for higher long-run growth but legally becomes the child's at adulthood and can affect financial aid; and a 529 plan offers tax-free growth specifically for education. For a long horizon, investing for growth typically far outpaces a cash savings account — though it adds volatility, which matters less the earlier you start and the longer the runway. Two caveats this calculator doesn't model: investment income above certain thresholds in a child's account can trigger the 'kiddie tax,' and account fees erode returns, so favor low-cost options. The biggest lever, by far, is starting early and contributing consistently — time, not the size of the monthly deposit, is what turns small regular savings into a substantial sum by adulthood.
Frequently Asked Questions
How is the kids savings account growth calculated?
The starting amount and each monthly contribution compound at the expected return (annual rate ÷ 12 per month). $500 plus $50/month for 18 years at 5% grows to about $18,688, with roughly $7,388 of that being growth.
What account should I use for a child?
Options include a basic kids' savings account or CD (simple, safe, low-return), a custodial UGMA/UTMA account (can be invested for growth but becomes the child's at adulthood and may affect aid), or a 529 plan (tax-free growth for education). Choose based on purpose, your desired control, and tax treatment.
Should the account be cash or invested?
Over a long horizon, investing for growth typically far outpaces a cash savings account, and the early start gives time to ride out volatility. For money needed soon or that can't drop, cash or CDs are safer. Match the expected return in this calculator to how the account is actually held.
Are there taxes on a child's investment income?
Possibly. Investment income above certain thresholds in a child's account can trigger the 'kiddie tax,' which taxes some of it at higher rates. The rules and thresholds change, so for larger balances consult a tax professional. Tax-advantaged options like a 529 avoid this for qualified education use.
Why does starting early matter so much?
Because time is compounding's biggest lever. Starting at birth gives nearly 18 years for growth, so even small monthly amounts build substantially. Waiting until the child is older sharply reduces the final amount — the same contributions have far fewer years to compound. Start early, contribute consistently.
Related Calculators
Data Sources & Benchmarks
This calculator draws on 1 independent, dated source. The starting values for expected annual return are taken from the benchmarks below and refresh whenever the snapshots are updated.
Methodology & Review
The future value compounds a starting balance and a fixed monthly contribution at the annual return, compounded monthly. It assumes deposits at month end and a constant return; it ignores tax, account fees, and any 'kiddie tax' on investment income above thresholds.
Written by Ugo Candido · Last updated May 22, 2026.