How Much Will My Retirement Savings Grow?

The split is the point, not the total

$25,000 now, $500 a month, 30 years, 7% assumed:

You put in	$205,000
Growth added	$607,898
Projected value	$812,898

Growth is 74.8% of the total.

A single projected figure hides that completely — which is why the calculator always shows the two halves apart. The ratio between them is the whole argument for starting early, and over long periods it crosses over quite suddenly rather than gradually. That crossover is what compounding looks like from the inside.

Five more years beats a bigger contribution

The single most persuasive number here:

Years	Projected	Growth share
30	$812,898	74.8%
35	$1,188,181	80.2%

Those five extra years add $375,283 — for $30,000 of extra deposits.

The gap is more than twelve times the money that produced it. Almost all of it is growth on contributions that now have longer to work.

That's why years added at the start of a working life are worth so much more than the same years added at the end. Early contributions are the ones with the longest runway.

The return assumption is doing most of the work

7% is a common assumption, not a fact — and it dominates the answer.

Long-run historical averages for broad stock markets are often quoted around 7–10% before inflation. But nobody knows what the next thirty years will do, and the sequence of returns matters as well as the average.

Run it at two or three assumptions. The spread between them tells you how much of the projection is arithmetic and how much is hope.

These are nominal dollars

Not adjusted for inflation. Over 30 years, that's a very large omission — the final figure buys substantially less than the same number would today.

The fix is simple: enter a real return instead. Roughly your expected return minus expected inflation.

7% expected with 3% inflation becomes 4% — and the projection drops from $812,898 to $429,862, with growth falling to 52.3% of the total.

Smaller. Considerably more honest. That's the number worth planning against.

Why the starting balance matters less than it feels like it should

$25,000 sitting there today is real money, and it's easy to treat it as the foundation of the projection.

It isn't. Over 30 years at 7% that lump grows to roughly $203,000 — meaningful, but almost exactly a quarter of the total. The other $610,000 comes from the $500 a month.

The calculator shows contributions alone ($180,000) separately from the total you put in ($205,000) for that reason. What you're building is mostly made of the habit, not the head start.

That cuts both ways, and it's the encouraging direction: starting from nothing costs you the lump's growth, not the plan. Someone beginning at zero with the same monthly contribution still reaches roughly $610,000 over the same period.

What it doesn't model

Four things, each of which matters:

Fees. They compound against you exactly as returns compound for you. A percentage point of fees over decades costs about what a percentage point of return gains — so subtract them from your return assumption rather than ignoring them.

Taxes. Entirely dependent on account type and jurisdiction.

Employer matching. If you get it, add it to the monthly figure. It's the highest-return money in this entire calculation.

Sequence of returns. Matters little at the start and a great deal near retirement — a bad few years just as you begin drawing down does far more damage than the same years early on.

What it's actually good for

Comparing scenarios against each other.

Five more years against a higher contribution. One return assumption against another. Nominal against real.

The relationships it shows are far more reliable than any single figure it produces — because every assumption feeding it is doing more work than the formula is.

Print the projection sheet — it has a scenario table, because running it once and writing down one number is the least useful thing you can do with it.

Arithmetic on assumptions you supply. Not financial advice — it cannot know your circumstances, tax position or plans.