How Much to Save for College: 529 Rules of Thumb

🏦 $5–15 CPC cluster🎓 College Board 2025-26 data⏱️ 6 min read

A public in-state degree runs about $25,350 a year at today's published prices, and it'll cost more by the time your kid enrolls. The good news buried in the math: starting early does most of the work. Fully funding a 529 for in-state public costs $563 a month from birth, but $1,576 if you wait until age 12. Here's the framework, the numbers by age, and the rules that keep parents sane.

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What college actually costs (2025-26)

SectorTuition & feesApprox. all-in year
Public 4-year, in-state$11,950≈$25,350
Public 4-year, out-of-state≈$32,700≈$46,100
Private nonprofit≈$45,000≈$59,900
Public 2-year, in-district≈$4,150

College Board's 2025-26 data puts in-state tuition and fees at $11,950, up 2.7% from the year before, with room and board adding roughly $13,400. Sticker prices run well ahead of what most families pay after grants: published prices are the worst case, and the average net price at publics is thousands lower.

Run your child's exact numbers

Age, school type, current balance, and contribution in; projected cost, coverage, and the monthly number that closes the gap out.

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The monthly numbers, by age

Child's age when you startIn-state, full fundingOne-third rule target
Newborn$563/mo≈$190/mo
Age 4$711/mo≈$235/mo
Age 8$972/mo≈$325/mo
Age 12$1,576/mo≈$525/mo
Age 15$3,078/mo≈$1,025/mo

Assumes 4% college cost inflation and 6% investment returns, starting from zero, covering the full four-year sticker. The one-third column applies the rule below. The pattern matters more than any single cell: every year you wait, the required contribution steps up, and after age 10 the curve gets steep.

The one-third rule

Most planners now recommend splitting college costs three ways: one-third from savings, one-third from current income during the college years, and one-third from grants, scholarships, and reasonable loans. Families who try to pre-pay 100% often shortchange retirement, the one goal with no scholarship program. The rule also happens to be realistic: paying $9,000 a year out of earnings while a kid is in school is ordinary; paying $25,000 a year out of earnings usually isn't.

For a newborn targeting an in-state public, one-third funding means about $190 a month. That's the number that fits real budgets, and it's why the calculator shows you the coverage percentage rather than only the full-funding figure.

Tuition inflation: what to assume

The scary "college costs rise 7% a year" statistic is decades stale. Reality check: in-state tuition rose 2.7% for 2025-26, and the ten-year average has run roughly 2% to 3% a year. So why do planners still model 4% to 5%? Because tuition spikes cluster in recessions, when state budgets get cut, exactly when your investments are also down. Assuming 4% is deliberately conservative; assuming 7% is paying for anxiety you probably don't need. Whatever you choose, the point of a projection is a target, not a prophecy; you'll re-run it every year.

Why 529s beat taxable accounts

Contributions grow federal-tax-free and come out tax-free for qualified education expenses. Over 18 years on a newborn's account, the tax-free compounding is worth tens of thousands compared with a brokerage account spinning off taxable gains. Add the state tax angle: more than 30 states plus D.C. deduct contributions or grant credits, worth, for example, about $495 a year to an Illinois couple contributing $10,000, or $1,000 straight back for an Indiana contributor. The full state-by-state table lives in the calculator.

What if my kid doesn't go to college?

The old knock on 529s, "what if they get a scholarship or skip college?", has mostly been legislated away. Today you can change the beneficiary to a sibling or nearly any family member, hold the account for graduate school, withdraw up to the scholarship amount with no penalty (earnings taxed, no 10% hit), pay up to $10,000 in student loans or K-12 tuition, and, since 2024, roll up to $35,000 lifetime into the beneficiary's Roth IRA. The money is far more flexible than its reputation.

Financial aid, briefly

A parent-owned 529 reduces aid eligibility by at most 5.64% of the account's value each year, and under the simplified FAFSA, qualified withdrawals no longer count as income at all. Translation: $20,000 in a 529 costs at most about $1,128 in aid eligibility, and usually less. Not saving to "qualify for more aid" trades a certain dollar for a maybe-dollar.

Questions people also ask

How much should I save for college by my child's age?

One widely-used benchmark: aim to have about 50% of the projected cost of a public in-state degree saved by age 18 if you're following a savings-heavy plan. By the halfway point (around age 9), roughly 25% to 30% saved keeps you on track. More practical for most families: a fixed monthly amount started early beats catch-up savings. Fully funding a public in-state 529 takes $563 a month from birth, $972 from age 8, and $1,576 from age 12.

What is the one-third rule for college costs?

A common planning split: one-third from savings, one-third from current income during the college years, and one-third from grants, scholarships, and reasonable student loans. It keeps families from over-saving at the expense of retirement, and it means your monthly 529 target is about one-third of the full-funding number.

What happens to a 529 if my child doesn't go to college?

You have options, and none involve losing the money to penalties by default. You can change the beneficiary to a sibling or another family member, keep the account for graduate school, withdraw up to a scholarship amount penalty-free, use it for qualified K-12 tuition or up to $10,000 in student loans, or roll up to $35,000 lifetime into the beneficiary's Roth IRA under SECURE 2.0.

Should I save for college or retirement first?

Retirement first. Your child can borrow for school; you cannot borrow for retirement. Capture any employer 401(k) match before funding a 529, and treat college savings as the next priority after that. The one-third rule exists precisely so parents don't raid their future to fully pre-pay a degree.

Educational estimates, not tax or investment advice. Projections use simple compound growth and ignore market volatility and plan fees; state deduction rules change often, so verify limits with your state's plan or a tax professional.

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