Your Roth IRA's future value depends on three inputs: annual contributions, average annual return, and time horizon. The compound-interest formula is: FV = P × ((1 + r)n − 1) / r, where P is the annual contribution, r is the annual return, n is the number of years. $7,500/year at a 7% real return for 30 years compounds to roughly $755,000 — entirely tax-free in a Roth IRA. The exact number depends on your inputs; the math doesn't lie about the power of starting early.
Quick Facts
- check_circleCompound interest formula: FV = P × ((1+r)^n − 1) / r
- infoHistorical real returns (after inflation): S&P 500 ~7%, total bond market ~2-3%, balanced portfolio ~5-6%.
- info$7,500/year at 7% for 30 years = ~$755,000. Same contribution at 5% real = ~$498,000. Difference: $257,000 from 200 basis points of return.
- warningPast returns aren't future returns. Use real (inflation-adjusted) returns for retirement planning to keep purchasing-power assumptions consistent.
- check_circleUse the Growth Projection tool to model your specific contribution + return + time horizon scenarios.
The Compound-Interest Math
For a constant annual contribution P at the end of each year, growing at rate r for n years:
FV = P × ((1 + r)n − 1) / r
Worked example: $7,500/year, 7% real return, 30 years.
- (1.07)30 = 7.612
- (7.612 − 1) / 0.07 = 94.46
- $7,500 × 94.46 = $708,450
That's the end-of-year version. If contributions are made at the START of each year (more accurate for annual lump-sum contributors), multiply by an additional (1+r): $708,450 × 1.07 ≈ $758,000. Round to ~$755,000 in real (after-inflation) dollars.
Real returns (after inflation) matter more than nominal returns for retirement-planning. A 10% nominal return with 3% inflation = ~7% real return. The math above uses real returns throughout for consistent purchasing-power projections.
Worked Examples by Starting Age
$7,500/year contribution, 7% real return:
| Start age | Years to 65 | Total contributed | Roth IRA value at 65 |
|---|---|---|---|
| 25 | 40 | $300,000 | ~$1,600,000 |
| 30 | 35 | $262,500 | ~$1,109,000 |
| 35 | 30 | $225,000 | ~$755,000 |
| 40 | 25 | $187,500 | ~$507,000 |
| 45 | 20 | $150,000 | ~$329,000 |
| 50 | 15 | $112,500 | ~$201,000 |
The 25-year-old's $300,000 of total contributions becomes $1.6M; the 50-year-old's $112,500 becomes $201,000. Same dollar-per-year, same return — but 40 years of compounding vs. 15 years is the dominant variable.
Sensitivity to Return Assumption
$7,500/year for 30 years, varying return:
- 4% real: ~$437,000
- 5% real: ~$523,000
- 6% real: ~$632,000
- 7% real: ~$755,000
- 8% real: ~$910,000
- 9% real: ~$1,103,000
The range is wide. A 200-basis-point swing in the assumed return (5% vs. 7%) changes the end balance by ~$232,000 over 30 years. Don't anchor on a single number — model multiple scenarios.
Conservative planning often uses 5% real for diversified portfolios; aggressive uses 7-8%. The S&P 500's historical real return is ~7% over rolling 30-year periods, but specific 30-year windows have ranged from 4% to 11%.
What Could Change This Math
- Contribution limit increases. The 2026 limit is $7,500. Indexed limits will rise — by 2055 the limit is likely to exceed $15,000 in nominal terms (~$10,000 in 2026 real terms). Higher contributions = higher final balance.
- Sequence-of-returns risk. Average return over 30 years tells you the geometric mean, but bad returns early followed by good ones produce a different end balance than the reverse. For accumulation phase, this is a small risk; for decumulation, it's the dominant risk.
- Fees. A 1% expense ratio over 30 years cuts the end balance by ~25-30%. Use the Fee-Drag Calculator to see the impact.
- Withdrawals before retirement. Pulling contributions out (which the IRS allows tax-free) breaks compounding on the withdrawn dollars.
- Tax-rate changes. The Roth IRA's tax-free withdrawal benefit is contingent on Congress not changing IRC §408A. Most projections assume current rules; changes would affect the after-tax value of the projected balance.