College Savings Calculator: Monthly Amount to Save

Is $622.97 a month the right college saving?

On the defaults — a $120,000.00 target college cost, 10 years until enrollment, a 6% expected annual return, and $10,000.00 already saved — the $10,000.00 grows to $17,908.48, leaving $102,091.52 still to save, which is $622.97 a month; you will pay in $74,756.40 and earn $35,243.60 of interest. A four-year degree at an in-state public university commonly costs past $100,000 all-in, and private colleges cost far more; college costs rise roughly 3% a year, faster than general inflation. A 529 plan lets savings grow tax-free when spent on education, and a 6% long-run return is a common planning assumption for a balanced investment mix — an assumption, not a promise.

Five things about the model are worth stating plainly. First, the future value of what you already have is the current savings times one plus the return, raised to the years — $10,000.00 × 1.06^10 = $17,908.48. Second, the amount still to save is the target minus that future value — $120,000.00 − $17,908.48 = $102,091.52. Third, the monthly payment spreads that amount over 120 months at 0.5% a month — $102,091.52 × 0.005 ÷ ((1.005)^120 − 1) = $622.97. Fourth, the total you will pay in is the monthly payment times the months — $622.97 × 120 = $74,756.40. And fifth, the interest earned is the target minus what you already had minus what you pay in — $120,000.00 − $10,000.00 − $74,756.40 = $35,243.60; all listed in Accuracy & limitations.

The worked example, line by line

Setup: $120,000.00 target college cost, 10 years until enrollment, 6% expected annual return, $10,000.00 current savings.

Line 1 — the future value of what you already have. The future value is $10,000.00 × 1.06^10 = $17,908.48.

Line 2 — still to save. The amount still to save is $120,000.00 − $17,908.48 = $102,091.52.

Line 3 — the monthly payment. The monthly rate is 6% ÷ 12 = 0.5% a month and there are 120 months, so the monthly payment is $102,091.52 × 0.005 ÷ ((1.005)^120 − 1) = $622.97.

Line 4 — total you will pay in. The total paid is $622.97 × 120 = $74,756.40.

Line 5 — interest earned. The interest earned is $120,000.00 − $10,000.00 − $74,756.40 = $35,243.60.

Line 6 — the check. $10,000.00 + $74,756.40 + $35,243.60 = $120,000.00, the target.

Every branch, checked

Target college cost $200,000.00: Future value of current savings $17,908.48, still to save $182,091.52, monthly saving $1,111.13, total paid $133,335.60, interest earned $56,664.40 — A $200,000.00 target needs $1,111.13 a month — the same $17,908.48 of growth from the $10,000.00 already saved, so the whole extra $80,000.00 of cost lands on the monthly payment.

Years until enrollment 5: Future value of current savings $13,382.26, still to save $106,617.74, monthly saving $1,528.13, total paid $91,687.80, interest earned $18,312.20 — With only 5 years the $10,000.00 grows to just $13,382.26, so $106,617.74 is still to save in 60 months — $1,528.13 a month, nearly two and a half times the 10-year figure.

Expected annual return 8%: Future value of current savings $21,589.25, still to save $98,410.75, monthly saving $537.92, total paid $64,550.40, interest earned $45,449.60 — At 8% the $10,000.00 grows to $21,589.25, leaving $98,410.75 to save — $537.92 a month. A higher assumed return lowers the monthly amount, but it is an assumption, not a promise.

Current savings $0.00: Future value of current savings $0.00, still to save $120,000.00, monthly saving $732.25, total paid $87,870.00, interest earned $32,130.00 — Starting from nothing means the full $120,000.00 is still to save — $732.25 a month, $109.28 a month more than with $10,000.00 already saved.

Current savings $50,000.00: Future value of current savings $89,542.38, still to save $30,457.62, monthly saving $185.85, total paid $22,302.00, interest earned $47,698.00 — With $50,000.00 already saved it grows to $89,542.38 on its own, leaving only $30,457.62 to save — $185.85 a month.

Target college cost $60,000.00: Future value of current savings $17,908.48, still to save $42,091.52, monthly saving $256.84, total paid $30,820.80, interest earned $19,179.20 — Halving the target to $60,000.00 leaves $42,091.52 to save — $256.84 a month, less than half the $622.97, because the $10,000.00 already saved still grows to $17,908.48.

Years until enrollment 18: Future value of current savings $28,543.39, still to save $91,456.61, monthly saving $236.11, total paid $50,999.76, interest earned $59,000.24 — Starting at birth gives the $10,000.00 eighteen years to grow to $28,543.39, leaving $91,456.61 to save over 216 months — $236.11 a month.

The reverses, worked backwards

Smallest whole-dollar target for the monthly saving to reach $1,000.00: At the displayed $181,788 the monthly saving is $1,000.00, the total paid is $120,000.00 and the interest is $51,788.00. At $181,787 the monthly saving is $999.99 — one dollar of target short.

Smallest whole number of years for the monthly saving to fall to $500.00 or less: At the displayed 12 years the monthly saving is $475.27, the future value is $20,121.96, the total paid is $68,438.88 and the interest is $41,561.12. At 11 years the monthly saving is $542.16 — above $500.

Smallest return (in 0.1% steps) for the monthly saving to fall to $500.00 or less: At the displayed 9.0% the monthly saving is $497.77, the future value is $23,673.64, the total paid is $59,732.40 and the interest is $50,267.60. At 8.9% the monthly saving is $501.72 — above $500.

Smallest whole-dollar current savings for the monthly saving to fall to $500.00 or less: At the displayed $21,253 the monthly saving is $500.00, the future value is $38,060.89, the total paid is $60,000.00 and the interest is $38,747.00. At $21,252 the monthly saving is $500.01 — above $500.

Largest whole-dollar target for the monthly saving to stay at $750.00 or less: At the displayed $140,818 the monthly saving is $750.00, the total paid is $90,000.00 and the interest is $40,818.00. At $140,819 the monthly saving is $750.01 — above $750.

Smallest whole-dollar current savings for no monthly saving at all: At the displayed $67,007 the future value is $119,999.33, leaving $0.67 still to save — which rounds to a monthly saving of $0.00, a total paid of $0.00 and interest of $52,993.00. At $67,006 the monthly saving is $0.02 — not zero yet.

What the defaults assume

The defaults are a $120,000.00 target college cost, 10 years until enrollment, a 6% expected annual return, and $10,000.00 of current savings — Future value of current savings $17,908.48, still to save $102,091.52, monthly saving $622.97, total paid $74,756.40, interest earned $35,243.60. With a Target college cost $200,000.00, Future value of current savings $17,908.48, still to save $182,091.52, monthly saving $1,111.13, total paid $133,335.60, interest earned $56,664.40 — A $200,000.00 target needs $1,111.13 a month — the same $17,908.48 of growth from the $10,000.00 already saved, so the whole extra $80,000.00 of cost lands on the monthly payment. With a Years until enrollment 5, Future value of current savings $13,382.26, still to save $106,617.74, monthly saving $1,528.13, total paid $91,687.80, interest earned $18,312.20 — With only 5 years the $10,000.00 grows to just $13,382.26, so $106,617.74 is still to save in 60 months — $1,528.13 a month, nearly two and a half times the 10-year figure. With a Expected annual return 8%, Future value of current savings $21,589.25, still to save $98,410.75, monthly saving $537.92, total paid $64,550.40, interest earned $45,449.60 — At 8% the $10,000.00 grows to $21,589.25, leaving $98,410.75 to save — $537.92 a month. A higher assumed return lowers the monthly amount, but it is an assumption, not a promise. With a Current savings $0.00, Future value of current savings $0.00, still to save $120,000.00, monthly saving $732.25, total paid $87,870.00, interest earned $32,130.00 — Starting from nothing means the full $120,000.00 is still to save — $732.25 a month, $109.28 a month more than with $10,000.00 already saved. With a Current savings $50,000.00, Future value of current savings $89,542.38, still to save $30,457.62, monthly saving $185.85, total paid $22,302.00, interest earned $47,698.00 — With $50,000.00 already saved it grows to $89,542.38 on its own, leaving only $30,457.62 to save — $185.85 a month. With a Target college cost $60,000.00, Future value of current savings $17,908.48, still to save $42,091.52, monthly saving $256.84, total paid $30,820.80, interest earned $19,179.20 — Halving the target to $60,000.00 leaves $42,091.52 to save — $256.84 a month, less than half the $622.97, because the $10,000.00 already saved still grows to $17,908.48. With a Years until enrollment 18, Future value of current savings $28,543.39, still to save $91,456.61, monthly saving $236.11, total paid $50,999.76, interest earned $59,000.24 — Starting at birth gives the $10,000.00 eighteen years to grow to $28,543.39, leaving $91,456.61 to save over 216 months — $236.11 a month. With Years until enrollment 0, Input error — the years until enrollment must be above 0; the calculator shows an error, not a result. With Current savings $150,000.00, Future value of current savings $268,627.15, still to save $0.00, monthly saving $0.00, total paid $0.00 — already covered — The $150,000.00 grows to $268,627.15 — already more than the $120,000.00 target, so nothing more to save and the monthly saving is $0.00. With Expected annual return 0%, Future value of current savings $10,000.00, still to save $110,000.00, monthly saving $916.67, total paid $110,000.40, interest earned $0.00 — With no return there is no growth: the future value stays $10,000.00, $110,000.00 is still to save and the monthly saving is $916.67, so the total paid is $110,000.40 — 40 cents over the remaining, because $916.6667 rounds up to $916.67 a month. The interest is $0.00. With Target college cost $0.00, Future value of current savings $17,908.48, still to save $0.00, monthly saving $0.00, total paid $0.00 — already covered — A target of $0.00 means nothing to save for, so the monthly saving is $0.00. With Newborn, 18 years, target $250,000.00, return 7%, current $5,000.00, Future value of current savings $16,899.66, still to save $233,100.34, monthly saving $541.19, total paid $116,897.04, interest earned $128,102.96 — A newborn saving for a $250,000.00 education at 7% with $5,000.00 already saved: the $5,000.00 grows to $16,899.66, leaving $233,100.34 to save — $541.19 a month. With Target $500,000.00, 15 years, return 7%, current $25,000.00, Future value of current savings $68,975.79, still to save $431,024.21, monthly saving $1,359.86, total paid $244,774.80, interest earned $230,225.20 — A $500,000.00 target over 15 years at 7% with $25,000.00 saved: the $25,000.00 grows to $68,975.79, leaving $431,024.21 to save — $1,359.86 a month. With Years until enrollment 1, Future value of current savings $10,600.00, still to save $109,400.00, monthly saving $8,868.67, total paid $106,424.04, interest earned $3,575.96 — With one year left the $10,000.00 grows to just $10,600.00, leaving $109,400.00 to save in 12 months — $8,868.67 a month.

Output · formula · meaning

Who uses this

• The parent of a 10-year-old saving for a $120,000.00 degree: they learn the monthly amount is $622.97 — and they check the 18-year branch to see it fall to $236.11 if they had started at birth.
• The parent who waited and has 5 years left: they learn the monthly amount jumps to $1,528.13 — and they check the $21,253 reverse to see how much saved already would bring it back under $500.00.
• The saver with $50,000.00 already put away: they learn their money grows to $89,542.38 on its own, so the monthly amount is only $185.85 — and they check the $67,007 reverse to see the savings that would make the monthly amount $0.00.
• The planner testing a higher return: they learn at 8% the monthly amount is $537.92 — and they check the 9.0% reverse to see the return that would bring it under $500.00.

Accuracy & limitations

The math is first-principles: the future value is the current savings times one plus the return, raised to the years, rounded to cents; the amount still to save is the target minus that future value; the monthly payment is computed from the unrounded amount still to save at the monthly rate over the months, then rounded to cents half-up; the total paid is the displayed monthly payment times the months; the interest earned is the target minus the current savings minus the total paid. What the model cannot do is predict your actual return: the 6% is an assumption, not a promise, and a bad decade can leave the fund well short; the target is today’s cost, but college costs rise roughly 3% a year, so a $120,000.00 target in 10 years may really be a $160,000.00 target; the calculator counts no taxes, fees, or financial aid; and it assumes you save the same amount every month, which a real budget rarely allows. Use it to set the monthly habit — then re-check the target and the return every year.

Frequently asked questions