529 Calculator

Formula audit and timing assumptions

The projection treats the stated annual investment return as an effective annual rate and converts it to an equivalent monthly rate:

Monthly rate = (1 + annual return)^(1/12) − 1

The current balance compounds until college begins. Monthly contributions are assumed to arrive at the end of each month, so their future value uses an ordinary-annuity factor:

Projected savings = current balance × (1 + monthly rate)^months + monthly contribution × [((1 + monthly rate)^months − 1) ÷ monthly rate]

When the return is 0%, the annuity factor is simply the number of contribution months. No division by zero is used.

Education costs are modeled as one annual cost at the beginning of each academic year. The first cost is inflated for the full number of years until college; each later year receives one more year of inflation:

Total education cost = Σ current annual cost × (1 + education inflation)^(years until college + academic year index)

Because later academic-year bills do not all have to be held as cash on the first day of college, the calculator also discounts years 2 onward back to the college-start date using the assumed investment return:

College-start funding goal = Σ projected annual cost ÷ (1 + annual return)^academic year index

Worked example

Assume a $25,000 balance, $500 contributed at each month-end, 10 years until college, a 6% annual return, $30,000 current annual cost, 4% education inflation, and four years of attendance.

The required monthly contribution solves the same future-value formula backward against the college-start funding goal. If the future value of the existing balance already covers that goal, the additional required contribution is zero. If college begins now and a gap remains, there are no contribution months left, so the calculator reports that a monthly contribution cannot close the gap before college starts.

Limits of the estimate

• Returns are assumptions, not guaranteed account performance.
• The college-start goal assumes the same return during attendance when discounting later annual costs. It does not simulate an actual withdrawal portfolio, taxes, fees, financial aid, scholarships, or changes in attendance.
• 529 plan rules, qualified expenses, state tax treatment, contribution limits, and financial-aid effects vary and can change. Confirm current rules with the plan and an appropriate tax or financial professional.
• Use the total education-cost input for tuition, housing, meals, books, transport, and other costs only to the extent they belong in your planning estimate. Not every expense is necessarily a qualified 529 withdrawal.