A walkthrough, end to end.
- 1
Enter your starting balance, expected annual return, monthly contribution, and time horizon.
- 2
The calculator runs the future-value annuity formula and gives the projected balance plus a breakdown of contributions vs. growth.
- 3
Try different return rates and contribution levels to see the leverage of consistency over time.
Future value of an annuity
Combines lump-sum compound growth on the initial balance with the future value of regular contributions made each period. Both components are summed for the total projected value.
What you can do with this.
Stock market historical returns
S&P 500 has averaged ~10% nominal / ~7% real (after inflation) since 1928. Use 7% as a conservative real-return assumption for long-horizon projections; 10% nominal is fine for shorter pre-retirement modeling.
Index fund vs individual stock projections
The 7–10% number is for diversified index funds (VOO, VTI). Individual stocks can blow this up or down by orders of magnitude — use the calculator only for index-fund-like portfolios.
Dollar-cost averaging math
Contributing $X every month vs. lump-sum $12X once a year produces nearly identical long-term outcomes (within 1–2%). DCA's value is behavioral consistency, not return optimization.
Power of starting early
Investing $500/mo from age 25 to 35 then stopping ends with MORE than starting at 35 and contributing $500/mo until 65. Time + compounding outweighs total amount contributed.
Inflation-adjusted projections
If you use a 7% return, that's already roughly real (after inflation). If using 10% nominal, subtract ~3% to get real purchasing power. Always project in real terms for retirement planning.
Roth IRA / 401k projections
Tax-advantaged accounts have a ~25% effective bonus over taxable accounts at most marginal brackets. Same math, but the final number represents tax-free spending in Roth — not directly comparable to taxable accounts.
Sequence-of-returns risk
This calculator assumes constant return. Real markets vary. A bad return sequence in early retirement can permanently impair the portfolio — Monte Carlo tools (Engineering-Your-FI, FICalc) handle this; this calculator gives the average outcome.
Investment calculator 2026 — what's current
10-year forward expected returns for US large-cap (per Vanguard's 2026 outlook) are 4–6% real, below the historical 7%. Plan with conservative assumptions; pleasant surprises are nicer than disappointments.
Frequently asked.
For long-term US stock-heavy portfolios, 7% real (or 10% nominal) is a defensible historical average. Bond-heavy portfolios trend toward 3–4% real. Pick the rate matching your asset allocation.
Total returns (price appreciation + dividends reinvested) are what 7%/10% historical figures already include. Don't add dividends separately — that would double-count.
Taxable account: subtract ~15–20% from gains for capital gains tax (or up to 37% for ordinary-income on dividends). Tax-advantaged accounts (Roth, 401k) skip this.
Yes — markets can go down for years. The calculator shows the average outcome. Diversification, time, and not panic-selling are your tools against losses.
No. Calculations run entirely in your browser.