The question most parents ask about college savings is 'should I open a 529 plan.' The more useful question — the one that actually helps you calibrate — is 'how much do I need to contribute each month to hit my target, given how old my child is right now.' The answer changes dramatically based on starting age, and the difference between starting at 5 versus starting at 8 can be $173/month in required contributions for the same $100,000 goal. That's $2,076/year more, for three fewer years of compounding.
This is the specific math guide. It covers what $100,000 actually covers in projected college costs, how much you need to contribute monthly at each starting age to hit that target, the 529 tax advantages that make this account worth using over a regular brokerage account, and the three things that genuinely change the calculation for your family.
What $100,000 Actually Covers in 2038-2041
The Target in Context of Projected Costs
A child who is 5 years old in 2024 will start college around 2037-2038. College costs have historically increased at approximately 3-4% per year above general inflation. Applying a conservative 3% annual increase to current costs:
Public university, in-state (2024 average: $11,260/year tuition and fees):
With room, board, and books, total cost of attendance approximately $28,000-$32,000/year currently. At 3% annual increase for 13 years: approximately $42,000-$48,000/year by 2037. Four-year total: $168,000-$192,000.
Public university, out-of-state (2024 average: ~$44,000/year total cost of attendance):
At 3% annual increase for 13 years: approximately $65,000/year by 2037. Four-year total: $260,000.
Private university (2024 average: ~$58,000/year total cost of attendance):
At 3% annual increase for 13 years: approximately $87,000/year by 2037. Four-year total: $348,000.
$100,000 in a 529 plan covers:
– Roughly 55-65% of a public in-state four-year degree
– Roughly 38% of a public out-of-state degree
– Roughly 29% of a private university degree
Most families don't aim to fund 100% of college costs from savings. The typical planning framework is 33-50% from savings (the 529), with the remainder covered by scholarships, grants, student work, and manageable loan amounts. A $100,000 529 balance at college entry is a meaningful and achievable target for a middle-class family that significantly reduces the loan burden on their child.
If your goal is closer to full funding — or if your child seems likely to attend a private or out-of-state school — the $200,000+ target is more appropriate. The monthly contribution math for a $200,000 goal is simply double the figures below.
Monthly Contribution Required by Child's Current Age
The Cost of Waiting, in Real Dollars
All calculations assume a 7% average annual return, which reflects the historical average return of a diversified stock-heavy portfolio over 10+ year periods. 529 plans invest in mutual funds and index funds — the same types of investments that produce this return in a brokerage account — with the added benefit of tax-free growth on qualifying withdrawals.
Start at birth (18 years to college):
Monthly contribution needed: $236/month
Total contributed: $50,976
Investment growth provides: $49,024 of the $100,000
Start at age 2 (16 years to college):
Monthly contribution needed: $276/month
Total contributed: $52,992
Investment growth provides: $47,008
Start at age 5 (13 years to college):
Monthly contribution needed: $406/month
Total contributed: $63,336
Investment growth provides: $36,664
Start at age 8 (10 years to college):
Monthly contribution needed: $579/month
Total contributed: $69,480
Investment growth provides: $30,520
Start at age 10 (8 years to college):
Monthly contribution needed: $759/month
Total contributed: $72,864
Investment growth provides: $27,136
Start at age 12 (6 years to college):
Monthly contribution needed: $1,074/month
Total contributed: $77,328
Investment growth provides: $22,672
Start at age 15 (3 years to college):
Monthly contribution needed: $2,551/month
Total contributed: $91,836
Investment growth provides: $8,164
Notice the pattern: the later you start, the more you contribute in total AND you get less investment growth to help. Starting at birth versus starting at age 12 means contributing $26,352 less in total contributions, while investment growth provides more than double the work. Compound interest rewards early starters in both directions.
If your child is already 5-8 years old and you haven't started a 529, the contribution required may feel steep. Two practical approaches: start with a smaller amount ($200-300/month) and step it up annually as income grows, or accept a smaller 529 balance target ($50,000-$70,000) and plan for the child to contribute through work, loans, or scholarships for the remainder.
The 529 Tax Advantages: Why This Account vs a Regular Account
The Free Government Boost You Get by Using the Right Account Type
You could invest for college in a regular taxable brokerage account — the same index funds, the same returns — and it would mostly work. But you'd pay annual taxes on dividends and capital gains, and taxes again on gains when you sell the investments to pay tuition. A 529 plan eliminates both of those taxes on money used for qualifying education expenses.
On $100,000 in investment gains in a taxable account, assuming 15% long-term capital gains tax: you lose $15,000 to taxes. In a 529 plan, that $15,000 stays in the account and goes toward tuition. The 529 advantage on a 13-year, $100,000 goal is roughly $8,000-$15,000 in avoided taxes, depending on your bracket and dividend income along the way.
State income tax deductions: Approximately 35 states offer a state income tax deduction or credit for 529 contributions. In states like New York, deductible up to $5,000/year (single) or $10,000/year (married). In Indiana, a 20% tax credit up to $1,500/year. Check your state's specific benefit — it can add $200-$1,500/year in real tax savings on top of the growth advantage.
New SECURE 2.0 rollover provision (2024+): One of the persistent objections to 529 plans was 'what if my child doesn't go to college — I'm stuck with a tax penalty on the money.' The SECURE 2.0 Act created a partial solution: starting in 2024, unused 529 funds can be rolled over to a Roth IRA in the beneficiary's name, up to $35,000 lifetime, subject to annual Roth IRA contribution limits. The 529 must have been open for at least 15 years. This means excess 529 savings for a child who gets a scholarship or doesn't need the full balance can become a Roth IRA head start for that child — a genuinely useful outcome. Our guide to how Roth IRA contribution limits, income rules, and investment choices work covers how this rollover intersects with normal Roth contribution rules.
Should You Fund a 529 Before Maxing Retirement Accounts?
The Priority Order Question Most Parents Ask
The standard financial planning answer: retirement first, then college savings. The reasoning is sound. You can borrow for college. You cannot borrow for retirement. Your child has 40+ years to pay off manageable student loan debt; you don't have 40 years to rebuild a depleted retirement account in your 50s.
The practical priority order for most families:
1. Capture full employer 401k match (100% instant return, always first)
2. Build 3-6 month emergency fund
3. Max Roth IRA ($7,000/year in 2024)
4. Increase 401k contribution (toward $23,000 limit)
5. Open and fund 529 plan
6. Taxable brokerage or additional savings
For families where retirement savings are on track, funding both retirement accounts and a 529 simultaneously is completely reasonable. The challenge is when parents feel pressure to fund the 529 at the expense of their own retirement. A child with $0 in a 529 plan but parents who will retire comfortably is in a better family financial position than a child with $100,000 in a 529 and parents who will depend on Social Security alone. For context on what retirement savings benchmarks look like at 30, 35, and 40 — and whether your own retirement trajectory is on track before adding the 529 obligation — see our savings benchmark guide covering how much you should have saved at each stage of your career to retire comfortably.
Where to Open a 529 Plan and What to Invest In
The Specific Account Setup
You are not required to use your home state's 529 plan (unless your state's tax deduction is only available for in-state plan contributions — check this first). Consistently top-rated plans available to all US residents:
Utah my529: No fees on most investment options, excellent age-based index fund portfolios, FDIC-insured option available. Accessible to any US resident at my529.org.
Fidelity-managed plans: New Hampshire (Fidelity Index Investments Plan) has no fees on Fidelity index fund investments. Excellent for Fidelity account holders who want everything in one place.
Vanguard 529 (Nevada): Nevada's plan managed by Vanguard, low expense ratios on index fund options. Good choice for Vanguard-oriented investors.
What to invest in: An age-based portfolio that automatically shifts from equity-heavy (80-100% stocks) to conservative (40-60% bonds) as your child approaches college age. This is the standard approach and appropriate for most families. For a 5-year-old with 13 years until college: an aggressive or moderate-aggressive portfolio (80-90% equities) is appropriate and what produces the 7% return assumption in the calculations above.
For the family where a 529 plan is the right next step after retirement accounts are funded, a comprehensive college savings and financial aid guide is a good companion read — particularly the chapters on FAFSA impact (529 plans count as parental assets at 5.64% in the financial aid formula, much lower than student-owned assets at 20%), how grandparent-owned 529 plans work, and how to choose between the 529 and other education savings vehicles. And since the 529-to-Roth IRA rollover provision makes the investment strategy inside the 529 matter more than ever, understanding how to choose index funds with the lowest expense ratios — the same principles discussed in our analysis of when to use a taxable brokerage account versus a 401k after your Roth IRA is maxed — applies directly to 529 fund selection. A college admissions and financial aid guide rounds out the picture, since the amount you need from a 529 plan depends significantly on what your child is likely to receive in merit and need-based aid — factors worth estimating early rather than assuming the full sticker price.