How much does $500 a month grow to in 30 years?

Saving $500 a month when you are starting from zero

Most people who search for this question are not sitting on a lump sum. They have a paycheck, a rough idea of what they can set aside, and a long stretch of working years ahead. This page takes that situation literally. The initial amount is zero, so every dollar in the final balance traces back to one of the monthly deposits or to growth earned on them. Five hundred dollars a month is a common target because it is large enough to matter and small enough to keep up through ordinary years, and thirty years is roughly the distance between a first serious job and the age many people start thinking about drawing on their savings.

The calculator walks through those thirty years one month at a time. At the start of each month it adds $500, then applies one month of growth to the whole balance: the 7% annual return divided by twelve, because the compounding setting is monthly. The very first deposit therefore earns growth for the full thirty years, while the last one, made at the start of the final month, earns a single month. Every deposit in between sits somewhere on that ladder. That is why the chart is not a straight line. The lower band is what you have paid in, rising by the same amount every year; the area above it is growth, and because growth is earned on earlier growth as well as on deposits, that area widens year after year.

Read the headline as the answer to a precise question: if the return averaged exactly 7% and you never missed a month, where would thirty years of $500 deposits end up before tax, fees and inflation. Real markets do not deliver the same return each year, so treat it as one point in a range rather than a forecast. The year-by-year table below the chart lets you check any single year, and the share link opens the main calculator with these same inputs filled in so you can adjust them there.

Why the starting amount is zero on this page

The main calculator opens with a $10,000 starting amount, which blurs a question many savers actually have: what does the habit alone produce. Setting the initial amount to zero isolates it. Everything above the contributions band in the chart comes from the deposits compounding on themselves. To see how much a head start would change the picture, type a starting amount into the first field, or pin this result on the comparison card and then change the years to see what starting five years later would cost.

Compound interest compared with simple interest

Simple interest pays a return only on the money you put in, never on earlier returns. The calculator works out that alternative for the same deposits so you can see what compounding itself adds. Your initial amount earns the stated rate once per year for the whole period, and each monthly deposit earns the same rate for the months it has been in the account, with nothing reinvested. The card that compares the two shows the simple-interest total and the difference between it and the compounded balance. Early on the two lines sit almost on top of each other, because the returns that could earn returns are still small. The gap opens slowly and then quickly, and in the chart it is the widening space between the curve and the straight line of contributions. That gap is the reason time in the account matters so much: most of it appears in the last third of a long period.

The rule of 72 and its exact form

The rule of 72 is a mental shortcut for doubling time: divide 72 by the annual return in percent and you get roughly how many years it takes for money to double with nothing added. At 6% the rule says 12 years. The exact answer comes from logarithms, the natural log of two divided by the natural log of one plus the rate, which at 6% gives about 11.9 years. At 9% the rule says 8 years and the exact figure is very close to it. The shortcut works because it is tuned for the middle of the range people usually use, and it drifts at very low or very high rates. The callout on the result shows both numbers for the rate you enter, so you can see how close the shortcut is. Doubling time applies to a single lump sum. With monthly deposits the balance grows faster than that, because new money keeps arriving.

What this calculator assumes, and what it leaves out

Every figure on this page comes from the same few assumptions. Deposits are made at the start of each month and never skipped. The annual return is constant for the whole period. Nothing is withdrawn. The results are before tax and before fees, and they are in future dollars, not adjusted for inflation, so a large balance decades from now will buy less than the same number would today. Taxes on interest and gains depend on the account type and where you live, and fund or platform fees reduce the return you actually keep, so a real account will usually end below the figure shown here. If you want a rough sense of the effect of fees, lower the annual return by the yearly cost you pay and run the numbers again. To think in today's money instead, enter a return that is already reduced by the inflation you expect. Neither adjustment is exact, but both move the projection closer to what you are likely to see.