Estimate what college will cost by the time you get there, what that bill is worth in today's dollars, and the monthly saving that would cover it — or a chosen share of it — from the savings you already have.
Formula
Each college year is inflated, then discounted at the after-tax return
r = return × (1 − tax):
cost_k = today × (1 + g)^(start + k)
total cost = sum of cost_k
today's money (PV) = sum of cost_k / (1 + r)^(start + k)
monthly saving = PMT of (PV − current savings) over (start + N) years
at a monthly rate r / 12
g is the college-cost increase rate, start is years until freshman year, and
N is the number of years attended. A 529 plan uses tax = 0 so r equals the
stated return.
College Board 2025–2026 published averages (tuition, fees, and living) are $65,470 private four-year, $30,990 in-state public, $50,920 out-of-state public, and $21,320 two-year public. Pick one to fill today's cost, or enter a net price from a specific school's calculator.
Average annual U.S. college cost (2025–2026)
| Type | Annual cost |
|---|---|
| 4-year private | $65,470 |
| 4-year public (in-state) | $30,990 |
| 4-year public (out-of-state) | $50,920 |
| 2-year public | $21,320 |
Source: the College Board (tuition, fees, and living).
Examples
Default plan (in-state public, 3 years out)
Today's annual cost $30,990, rising 5%, four years of college starting in 3 years, 35% paid from savings, no current balance, 5% return taxed at 25%. Total college cost is $154,625 ($130,836 in today's money). Covering the full bill takes $1,773 per month for 7 years. The 35% savings share is $54,119 ($45,792 today), or $621 per month.
Newborn, 65% from a 529
Today's cost $28,840, 5% increases, four years starting in 19 years, 65% from savings, $10,000 already saved, 7% return and 0% tax (a 529). Total cost $314,110 ($78,373 today). After the $10,000 already saved, the full bill needs $499 per month for 23 years; the 65% share needs $299 per month, with $47,370 due freshman year.