529 Plan: How Much You Actually Need to Save for College
Most 529 plan advice is vague. Here is the actual math — with real numbers, state tax breaks, and the overfunding fix that changed in 2024.
A 529 plan is the single best way to save for college in the US. Growth is tax-free. Withdrawals for qualified expenses are tax-free. And since 2024, you can roll unused funds into a Roth IRA. There is no real downside — only the mistake of not starting one.
The numbers that matter
College costs have risen about 5% annually for decades — roughly double the general inflation rate. A four-year public university now averages $28,000/year (in-state, including room and board). Private: $60,000/year. In 18 years, at 5% inflation, those numbers become $67,000 and $143,000 per year.
That means a child born today needs roughly $270,000 for a public university or $570,000 for a private one. Fully funding that requires $800–$1,700/month depending on your investment returns. Most families can't do that. The point is not to cover 100% — it is to cover enough that your child graduates with manageable debt, not crushing debt.
Enter your child's age, current balance, and monthly contribution — see exactly how much you'll have at college time and the funding gap.
Open the 529 Calculator →How the math works
A 529 grows through monthly compounding. Your annual return converts to a monthly rate. The future value formula accounts for your existing balance (growing as a lump sum) and your ongoing contributions (growing as an annuity). The calculator uses binary search to find the exact monthly contribution that fully funds the gap.
The key variables: child's current age, years until college, current balance, monthly contribution, expected return, current college cost, and cost inflation rate. Change any one of these and the required contribution shifts dramatically.
Worked example
Child is 5. College in 13 years. Current balance: $8,000. Monthly contribution: $300. Expected return: 6%. Current annual cost: $30,000. Cost inflation: 5%.
- Four-year total cost at inflation: ~$236,000
- Projected 529 balance at college start: ~$95,400
- Funding shortfall: ~$140,000
- To fully fund: increase contribution to ~$840/month
That $300/month gap is the difference between your child graduating debt-free and graduating with $140,000 in loans. The calculator shows you this number instantly.
State tax deductions: free money most people miss
About 30 states offer a tax deduction or credit for 529 contributions. This is not a federal benefit — it is state-level. The rules vary wildly:
- New York: up to $5,000 deduction (single) or $10,000 (married)
- Illinois: up to $10,000 deduction per taxpayer
- Indiana: 20% credit on contributions, up to $1,000 credit
- California, Florida, Texas: no state tax deduction
If your state offers a deduction, contribute at least enough to max it out. That is a guaranteed return on your money before any investment growth. If your state has no deduction, choose a plan based purely on fees and investment options — Vanguard-based plans in Nevada, Utah, and New York are consistently rated highest.
You can use any state's plan
The 2024 overfunding fix: 529 to Roth IRA rollover
Before 2024, overfunding a 529 was risky. If your child got a scholarship or chose not to college, you faced a 10% penalty on earnings for non-qualified withdrawals. The SECURE 2.0 Act changed this.
Starting in 2024, you can roll unused 529 funds directly into a Roth IRA for the beneficiary. Three rules: the account must be at least 15 years old, rollovers count against the annual Roth contribution limit ($7,000 in 2025), and the lifetime rollover cap is $35,000.
This does not make overfunding risk-free — $35,000 is a fraction of what a well-funded 529 might hold. But it removes the worst-case scenario. If your child does not need the money, it becomes tax-free retirement savings for them.
K-12 tuition: technically allowed, usually a bad idea
Since 2017, you can withdraw up to $10,000/year per student from a 529 for K-12 tuition. Federal tax-free. But most states do not conform to this rule for state tax purposes. In many states, K-12 withdrawals trigger state income tax and possibly a penalty on earnings. Check your state before using 529 funds for private school.
More importantly: the money you pull out for kindergarten is money that will not compound for 13 more years. At 7% annual return, $10,000 withdrawn at age 5 would have grown to $24,000 by age 18. Only use 529 funds for K-12 if you are already maxing out the plan and have no other source.
What to actually do
- Open a 529 now. Even $50/month starts the clock. The biggest cost of 529 plans is delay.
- Check your state's deduction. If one exists, contribute at least enough to max it.
- Use the calculator. Enter your real numbers. See the gap. Decide what you can afford.
- Set up automatic monthly contributions. Treat it like a bill, not a discretionary savings goal.
- Revisit annually. As your income grows, increase contributions. A 10% annual step-up nearly doubles your final balance over 18 years.
See exactly how much you need to save monthly to fully fund your child's college education.
Calculate Your 529 Savings Gap →Key Takeaways
- A 529 plan offers tax-free growth and tax-free withdrawals for education expenses.
- College costs inflate at ~5% annually — a four-year public university will cost ~$270,000 for a child born today.
- About 30 states offer tax deductions for 529 contributions. Max your state's deduction first.
- Since 2024, unused 529 funds can roll into a Roth IRA (up to $35,000 lifetime).
- The biggest 529 mistake is not starting one. Even small contributions compound significantly over 18 years.