What This Calculator Does

"How much will I actually have by the time I retire?" is a simpler question than most retirement planning tools treat it as, and this calculator answers just that part of it directly. Give it your current age, the age you plan to retire, what you've already saved, how much you'll add every year, and the growth rate you expect, and it projects your balance the year you retire, along with how much of it came from your own contributions versus investment growth. It also turns that balance into a rough monthly income estimate, and lets you add your own Social Security or pension estimate on top to get a fuller monthly income picture.

How to Use It

Enter Current Age and Retirement Age (the calculator needs the second to be later than the first, since it's projecting forward), then Current Savings, Annual Contribution, and Annual Growth Rate. The last field, Estimated Monthly Social Security/Pension, is optional — leave it at 0 if you'd rather see the savings projection on its own. Click Calculate and the Retirement Projection panel shows your projected Balance at Retirement, Years to Retirement, Total Contributions over that span, and Total Interest Earned, followed by an Estimated Monthly Income panel: your projected income from savings (using the common 4% withdrawal rule), your own SS/pension estimate, and the two added together as a Total Estimated Monthly Income. That total isn't a calculated benefit — the SS/pension portion is exactly whatever number you typed in, with no government formula applied to it.

The Formula

Each year runs the same two-step recurrence: first your annual contribution is added to the current balance, then the whole balance — savings plus that year's contribution — is grown by the annual rate. In other words, B = (B + contribution) × (1 + rate), repeated once per year for every year between your current age and your retirement age. Because the contribution is added before growth is applied each year, it earns a full year of growth in the very year it's made, rather than being tacked on at the end with no growth of its own.

The Estimated Monthly Income figures are a separate calculation layered on afterward — they never feed back into the balance projection above. Income from savings = Balance at Retirement × 4% ÷ 12 (the standard 4% annual withdrawal rule, converted to a monthly figure). Total Estimated Monthly Income = that number + your own monthly Social Security/Pension estimate, added exactly as entered with no adjustment or calculation applied to it.

A Worked Example

Someone who is 30 years old, plans to retire at 35, has $10,000 saved already, adds $5,000 a year, and expects 7% annual growth would see the balance evolve like this: year 1 takes ($10,000 + $5,000) × 1.07 = $16,050.00; year 2 takes ($16,050 + $5,000) × 1.07 = $22,553.50; and so on for five years total. By the end of year 5, the projected Balance at Retirement is $44,791.97. Total Contributions over those five years come to exactly $25,000 (five payments of $5,000), which means the remaining $9,791.97 of the final balance was earned purely through growth on the account.

From that same $44,791.97 balance, the 4% rule gives an Estimated Monthly Income from Savings of $149.31 ($44,791.97 × 4% ÷ 12). If that same person also enters $2,000 as their own Social Security/pension estimate, the Total Estimated Monthly Income becomes $2,149.31 — $149.31 from savings plus the $2,000 they typed in directly, unchanged.

Understanding the 4% Rule — and Its Real Limitations

The 4% rule comes from research (most commonly traced back to the "Trinity Study") that looked at historical U.S. market returns and asked: what withdrawal rate, taken from a retirement portfolio and adjusted for inflation each year, would have let that portfolio last at least 30 years across most historical starting points? 4% came out as a rate that held up in the large majority of those historical scenarios — not all of them, and not as a rate that guarantees a portfolio never runs out.

It's a widely-used planning guideline, not a promise. It doesn't account for market volatility in the years right around retirement — sequence-of-returns risk, where a few bad years early in retirement can do lasting damage to a portfolio that a much later bad year of the same size wouldn't, because withdrawals keep coming out of a shrunken balance before it has time to recover. It also doesn't account for unplanned healthcare costs, which tend to rise later in retirement and are one of the largest sources of budget surprises for retirees. This calculator applies the 4% figure as a flat, static rate to a single projected balance — a useful rough estimate to plan around, not a substitute for stress-testing a real retirement plan against market downturns and unexpected expenses.

How Contribution Consistency and Time Horizon Change the Outcome

Two variables tend to matter more than people expect: whether you keep contributing, and how long the money has to grow. Isolating contributions first — take the same $10,000 starting balance at the same 7% growth rate over the same 5 years used in the worked example above. With $5,000 added every year, it grows to $44,791.97. With no contributions at all, that identical starting balance only reaches $14,025.52 over the same 5 years. The $25,000 in contributions accounts for most of that $30,766.45 difference, but not all of it — the remaining $5,766.45 is growth earned on those contributions themselves, money that wouldn't exist if the contributions had been made all at once at the very end instead of steadily along the way.

Isolating time horizon next — take a $10,000 balance with no contributions at a flat 5% growth rate (the same rate and principal as the no-contribution worked example above). Over 3 years it reaches $11,576.25. Over 20 years, the same balance at the same rate reaches $26,532.98 — more than double, from time alone, with nothing else changing. This is the practical case for starting early: a longer horizon lets compounding do proportionally more of the work, even without adding a single extra dollar of contribution.