Investment Planner

The Investment Growth Planner projects how a starting lump sum plus regular contributions grow over time. It factors in your expected return, contribution frequency, and optional inflation adjustment. Unlike a simple compound interest calculator, it models the realistic investor scenario: a starting balance with ongoing contributions, and shows both nominal and inflation-adjusted growth side by side.

The difference between starting to invest at 25 versus 35 is not just 10 years of contributions. It is a decade of compounding on every dollar that follows. At $500/month and 7% annual return: starting at 25 gives about $2,413,000 at age 65. Starting at 35 gives about $1,197,000. The 10-year delay costs over $1.2 million — far more than the $60,000 in missed contributions. This is the compounding effect this planner shows you.

Who should use this calculator?

• Early-career investors establishing savings rates and contribution targets for 401(k), IRA, or taxable accounts.
• Mid-career accumulators assessing whether current savings trajectories are sufficient to meet retirement targets in real purchasing power terms.
• Goal-based planners working backward from a target balance (e.g., $2 million at retirement) to determine the required monthly contribution or required rate of return.
• Parents funding education projecting 529 plan growth alongside tuition inflation assumptions.
• Business owners comparing wealth accumulation in taxable accounts versus tax-advantaged retirement accounts (SEP-IRA, Solo 401(k)).

The SEC's investor education on compound interest puts it clearly: time in the market is the strongest driver of long-term wealth — stronger than timing, stock selection, or even the return rate within a reasonable range. Given enough years of consistent investing, annual gains eventually exceed annual contributions in dollar terms — the point where compounding takes over.

The investment planner combines two standard time-value-of-money formulas: the future value of a present lump sum (FV of PV) and the future value of an annuity (FV of PMT). Together they model the realistic investor scenario of both an initial deposit and ongoing contributions.

For beginning-of-period contributions (annuity due), multiply FV_annuity by (1 + r) for the extra period of compounding. Beginning-of-month contributions earn slightly more over long periods. Per FINRA, even small timing adjustments accumulate meaningfully over decades.

The planner works both forward (given inputs, what will I have?) and backward (given a target, what inputs do I need?). Walk through both approaches:

1. Enter your starting balance.
   Any existing investable asset — 401(k), IRA, taxable account, or $0 if starting fresh. Example: $25,000 existing Roth IRA balance.
   Tip: For goal-based planning, set this to $0 and see what regular investing alone achieves.
2. Set your periodic contribution and frequency.
   Enter the amount you plan to invest per period. Example: $600/month. Choose monthly, bi-weekly, quarterly, or annual.
   2026 limits per IRS: 401(k) $24,500 ($32,500 if 50+); IRA $7,500 ($8,600 if 50+). Maxing both means $32,000/year in tax-advantaged contributions.
3. Enter your expected annual return.
   Use a conservative assumption: stocks have historically earned more than bonds, and bonds more than cash, but no return is guaranteed. Run the plan at a lower rate as well to see how sensitive it is.
4. Set your time horizon and inflation rate.
   Time horizon: years until you need the money (e.g., 30 years). Inflation rate: 2.5–3.0% for conservative planning. The calculator shows both nominal and real future values so you can see what your projected balance is worth in today's purchasing power.
5. Run the reverse calculation for contribution targeting.
   Switch to "solve for contribution" mode and enter your target balance. Example: Target $1,500,000 real in 25 years at 7% nominal and 3% inflation. Required monthly contribution: ~$1,862 starting from $0, or ~$967 with $100,000 already invested. This shows the exact trade-off between time, return, and contribution.
6. Compare tax-advantaged vs. taxable growth.
   Toggle the tax-drag setting. A taxable portfolio at 8% with a 25% effective tax rate on gains and dividends effectively compounds at ~6%. Over 30 years on $10,000 + $500/month: tax-advantaged ≈ $605,000; taxable with 25% drag ≈ $482,000. That $123,000 gap is the value of tax deferral.

The planner gives you a complete picture of your wealth-building trajectory. Here is how to read each output.

Projected Final Balance (Nominal): The total dollar value at the end of the time horizon, if your inputs hold. For $10,000 start + $500/month at 7% for 30 years: $605,265. This is the account statement number — what your portfolio will read in 30 years, not what it buys.

Projected Final Balance (Real / Inflation-Adjusted): What your nominal balance buys in today's dollars. At 3% inflation over 30 years, $605,265 nominal has the purchasing power of about $249,600 today. To retire on $60,000/year in today's money, you need roughly $1,500,000 in real terms at a 4% withdrawal rate. The real FV output shows whether your plan gets there.

Total Contributions vs. Total Gains Chart: A dual-line chart of cumulative deposits vs. cumulative gains. Early in the timeline, contributions dominate. As years pass, gains accelerate and overtake contributions — the visual "hockey stick" of compounding. In the example: $190,000 in contributions vs. $415,265 in gains, more than twice the invested capital from compounding alone.

Year-by-Year Growth Table: A detailed schedule: beginning balance, contributions, return earned, ending balance per year. Use it to find milestone years and see the acceleration as the base grows. In year 1: investment gains ~$4,900. In year 30: annual gains exceed $39,700 — an 8× increase from the same 7% rate applied to a much larger base.

Rate of Return Sensitivity: The calculator shows your final balance across return scenarios (5%, 6%, 7%, 8%, 9%). The spread between 5% and 9% over 30 years on $500/month is enormous: 5% → $416,000; 9% → $907,000. As SEC education materials note, a 2–3% difference in annual return produces life-changing differences in wealth over long horizons — making asset allocation one of the most important decisions in personal finance.

• Max tax-advantaged accounts before taxable investing. Per IRS, the 2026 401(k) limit is $24,500 ($32,500 if 50+); IRA limit is $7,500 ($8,600 if 50+). Traditional contributions reduce taxable income dollar-for-dollar. In the 22% bracket, a $7,000 IRA contribution saves $1,540 in federal taxes right now. Reinvested over 30 years, those tax savings can add $120,000+ to final wealth — nearly as valuable as the investment return itself.
• Automate contributions and never skip months. Missing 12 contributions of $600 does not cost $7,200. It costs $7,200 plus decades of compounding. A 25-year-old who skips one year of $600/month contributions loses about $44,000 by age 65 at 7%. Set automatic monthly transfers on payday. Paying yourself first beats any investment selection decision.
• Increase contributions 1% per year with each raise. Capturing lifestyle inflation before spending habits adjust is the easiest way to grow savings. If your salary rises $3,000, redirecting $100/month to retirement costs nothing in felt spending power — but adds about $73,000 to your portfolio over 20 years at 7%. Many 401(k) plans offer "auto-escalation" that does this automatically each year.
• Don't confuse return rate with risk tolerance. A high long-run average return hides large year-to-year swings, and poor returns early in retirement can wreck a plan that looks fine on paper. Build the plan around a conservative return assumption and test it at lower rates too.
• Use the planner to quantify the cost of any financial decision. A $15,000 401(k) loan does not just cost $15,000. It costs $15,000 plus all the growth that money would have earned. At 7% for 5 years, $15,000 becomes $21,038. The planner shows the trajectory with and without the withdrawal, making the true opportunity cost clear. Cashing out a 401(k) during a job change instead of rolling it over destroys not just the balance but decades of compounding on that capital.
• For Canadian investors: TFSA and RRSP contribution optimization matters. The 2025 TFSA contribution limit is $7,000/year (cumulative room from 2009 up to $102,000), and RRSP contributions are deductible at your marginal rate (18% of prior year earned income, up to $32,490 in 2025). A common rule of thumb is RRSP-first when your marginal tax rate is high now and TFSA-first when it is low, since TFSA withdrawals are tax-free while RRSP withdrawals are taxable income (see the Canada Revenue Agency for the rules).