How Much Will My Child Have Saved by 18?
Enter what you're putting away each week and see what it reaches by their eighteenth birthday — plus what the same amount would have reached if you had started earlier or later.
What $10/week reaches by 18, by starting age
Same weekly amount, same 4% rate, starting from nothing — only the start age changes. The table updates as you change the inputs above.
| Start age | Years saving | You contribute | Balance at 18 |
|---|---|---|---|
| 4 | 14 | $7,280 | $9,754 |
| 5 | 13 | $6,760 | $8,862 |
| 6 | 12 | $6,240 | $8,005 |
| 7 | 11 | $5,720 | $7,182 |
| 8 | 10 | $5,200 | $6,391 |
| 9 | 9 | $4,680 | $5,631 |
| 10 | 8 | $4,160 | $4,900 |
| 11 | 7 | $3,640 | $4,199 |
| 12 | 6 | $3,120 | $3,525 |
| 13 | 5 | $2,600 | $2,877 |
| 14 | 4 | $2,080 | $2,255 |
| 15 | 3 | $1,560 | $1,657 |
| 16 | 2 | $1,040 | $1,082 |
| 17 | 1 | $520 | $530 |
How much will my child's savings grow by the time they turn 18?
It depends on three things: the weekly amount, the age you start, and the rate. The table below holds the first two fixed and changes only the rate, so you can see how much of the answer comes from the account. Each cell is the balance at 18 as 0.38% / 4% (national average / high-yield).
The account you pick changes the answer more than the age you start
| Weekly deposit | Start at 4 | Start at 8 | Start at 12 | Start at 16 |
|---|---|---|---|---|
| $5 | $3,738 / $4,877 | $2,650 / $3,195 | $1,578 / $1,762 | $522 / $541 |
| $10 | $7,477 / $9,754 | $5,300 / $6,391 | $3,156 / $3,525 | $1,044 / $1,082 |
| $20 | $14,954 / $19,508 | $10,600 / $12,781 | $6,311 / $7,049 | $2,088 / $2,165 |
| $40 | $29,907 / $39,015 | $21,199 / $25,563 | $12,623 / $14,099 | $4,176 / $4,329 |
Method: a deposit at the end of every week, interest compounded weekly, starting from a zero balance, the same as the calculator above. The 0.38% rate is the FDIC national average savings rate (fdic.gov national rates, effective 19 October 2026, checked 21 October 2026). The 4% rate is rounded down from the top APY of 4.27% on Bankrate's best high-yield savings list (bankrate.com, rates as of 19 October 2026). Bank rates change, so check a current list before relying on either figure. Not inflation-adjusted.
Why the early rows are so much larger
The gap between starting at 6 and starting at 12 is far wider than the six years of extra contributions would suggest. The early deposits have the longest time to compound, so each one contributes more than a later deposit of the same size. Money added at 17 barely compounds at all — it is essentially just saved.
That is also why the "cost of waiting one more year" figure above is usually larger than a year of deposits. You lose the contributions and the growth they would have produced.
What rate should you use?
For a real savings account, use whatever your bank actually pays. For a family bank where you pay the interest yourself, the rate is whatever you decide — see the compound interest calculator for what different rates cost you, and how to run a bank of mom and dad for how to set one up.
Set the rate to 0 to see contributions alone. The difference between that and your real rate is exactly what the interest is doing for you.
Track it without a spreadsheet
Bank of Dad keeps a running balance for each child, applies interest automatically on the schedule you set, and logs every deposit and withdrawal. Free to use. Optional Premium, $2.99/mo.
Frequently asked questions
How much should I save for my child each week?
There is no correct amount — it depends entirely on what your family can sustain. Consistency matters far more than size: $5 a week from age 6 reaches more by 18 than $15 a week started at 14, because the early deposits compound for twelve years instead of four.
Is it too late to start saving for my teenager?
No, but the maths changes. With four years left, interest contributes relatively little and the balance is close to what you put in. Set the rate to 0 in the calculator to see that directly. Saving still works; it just behaves like saving rather than like compounding.
How much will my child's savings grow by the time they turn 18?
It depends on the weekly amount, the start age and the rate. See the comparison table above for $5 to $40 a week at the FDIC national average rate and at a high-yield rate, or enter your own numbers in the calculator for a personalised figure.
What's a realistic interest rate to plug into this calculator?
The FDIC national average savings rate is 0.38% (effective 19 October 2026), which is a conservative floor. High-yield accounts pay several times that; Bankrate's list topped out at 4.27% APY on 19 October 2026. Rates move, so check a current rate table before assuming a number.
Does this account for inflation?
No. Every figure is in today's dollars at face value, so a balance shown for eighteen years from now will buy less then than the same number would buy today. Treat the output as a nominal balance, not as purchasing power.
Want the balance tracked for you?
Bank of Dad gives each child a savings account you control, applies interest automatically, and logs every transaction. Free to use. Optional Premium, $2.99/mo.
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