Retirement Savings Calculator
Around $1.6 million. That's what you land on at 65 if you put $1,000 away every month, earn 7% a year, and start today with just $50,000 saved. Scary or encouraging? Depends on where you're standing. This retirement savings calculator takes five numbers you actually know (your age, when you want to stop working, what you've saved, what you can put away each month, and a realistic return) and projects your balance at retirement. It splits the answer into what you deposited and what compounding added, so the math stops feeling abstract and starts looking like a plan.
How this retirement calculator works
Give it five numbers and it compounds them month by month until your retirement age, then shows the projected balance split into what you contributed and what returns added. That's the whole machine. Two engines, one number.
The first engine is what you've already saved. It sits there compounding untouched, like a snowball that started rolling before you were born. The second engine is your monthly deposit. Every single payment gets its own little growth runway, and the calculator adds up all of them. The split between the two is usually the surprise. Most people overestimate their own contributions and underestimate what compounding did on its own. The split makes the invisible half visible.
A few assumptions sit under the hood. The annual return is converted to a monthly rate, and deposits are assumed to land at the end of each month. (Deposits made at the start of the month would earn one extra month of growth each, a difference so small you can ignore it.) Returns are smooth, because no formula can predict crashes. Inflation, taxes, and fees are not modeled directly. If they worry you, use a lower return, like 5 or 6%, and let the conservative math protect you.
Formula
In plain language: P is what you've already saved. PMT is your monthly deposit. r is your annual return divided by 12, and n is the number of months between now and retirement. The first term grows today's savings untouched. The second term is the future value of every deposit you will ever make, each compounded for the months it has left. Add them together and you get the balance at retirement.
Example
Let's do one by hand so you trust the machine. You're 25, you have $0 saved, you invest $500 a month, you earn 7% a year, and you retire at 65. That's 40 years.
First, the monthly rate: 0.07 ÷ 12 ≈ 0.005833. Months: 40 × 12 = 480. The growth factor: (1.005833)480 ≈ 16.31. The annuity factor: (16.31 − 1) ÷ 0.005833 ≈ 2624.8. Multiply: $500 × 2624.8 ≈ $1,312,400.
The calculator says $1,312,407. The tiny difference is my rounding, not its math. Your deposits totaled $500 × 480 = $240,000. Growth added $1,072,407, about four and a half times what you put in. Your wallet covered a quarter of the final number. Time covered the rest.
How to read your results
Compare the projected balance to a target. The usual starting target is 25 times your expected annual spending in retirement. Plan to spend $60,000 a year? Your target is roughly $1.5 million. It's a rough guide, not a law, but it turns an abstract number into a pass or fail.
If you're short, you have three levers, and they're not equal. Raising the monthly deposit is the one you control most. Adding just $100 a month to the default plan (35 to 65, 7%) grows the balance by about $121,997. Small input, big output. Delaying retirement is lever two: one extra year near the end, when the balance is largest, adds roughly one year's worth of growth, close to 7% of the total. Spending less in retirement is lever three, and it's the most powerful on paper because the 25× rule multiplies every dollar you trim.
If you're ahead of target, you're in interesting territory. Once compounding alone can finish the job without new deposits, you've reached what early retirees call Coast FIRE. Our guide on how much you need to Coast FIRE at 35 walks through that exact scenario. And watch the curve, not just the final number. After 10 years the default plan holds $273,568 on $170,000 contributed. The first decade looks slow. The last decade does the sprint.
Scenario comparison
Same 7% return, three different starting ages, all retiring at 65. Read the last column first.
| Scenario | Monthly deposit | Total contributed | Final balance | From growth |
|---|---|---|---|---|
| Start at 25 ($5,000 saved) | $500 | $245,000 | $1,393,964 | 82% |
| Start at 35 ($50,000 saved) | $1,000 | $410,000 | $1,625,796 | 75% |
| Start at 45 ($150,000 saved) | $1,500 | $510,000 | $1,387,201 | 63% |
The 45-year-old deposits more than twice what the 25-year-old does and retires with slightly less. The 35-year-old lands the biggest balance mostly by having more time than the 45-year-old and more money than the 25-year-old. That's the whole lesson of this calculator in one table: time is the highest-paying input you own.
Frequently asked questions
How much do I need to retire comfortably?
What annual return rate should I use?
Does this calculator account for inflation?
I'm 50 with nothing saved. Is it too late?
Should I include Social Security or a pension?
How often should I re-run my numbers?
For the idea behind the target itself, read what Coast FIRE is — it reframes this projection as a finish line you can reach early and then coast past.
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Sources & methodology
The math here is the standard future-value formula: a lump sum compounded over n periods, plus the future value of a monthly annuity. Growth compounds monthly, and each deposit is assumed to land at the end of the month. Every calculation runs locally in your browser, which means no numbers are sent to a server or stored anywhere. Read our retirement calculation methodology page for the full set of assumptions in plain English.