Calculateur de croissance du patrimoine

Wealth Growth Calculator

Wealth grows through two forces working together: regular saving and compound investment returns. This calculator models both at once, projecting your net worth year by year based on your current savings balance, the amount you add each month, and the annual return rate you expect from your investments. Use it to set concrete milestones, measure how much a higher savings rate is worth over 20 years, or stress-test your plan against lower-return assumptions before retirement.

How Wealth Growth Is Calculated

Your projected wealth combines your current assets with all future contributions, each growing at a compounding rate from the day they are invested:

FV = PV(1 + r)^n + PMT x [(1 + r)^n - 1] / r

Where PV is your current savings or net worth, PMT is the periodic contribution amount, r is the return rate per period, and n is the total number of periods. The first term compounds your existing balance for the full time horizon. The second term treats each monthly contribution as a separate investment that compounds from the month it is made through to the end of the period. Both terms accelerate as the portfolio grows — a $200,000 portfolio earning 7% generates $14,000 in a single year, while a $500,000 portfolio earning the same rate generates $35,000 that year with no additional contributions required.

Worked Examples

Scenario 1 — Starting from scratch at 25: A 25-year-old with no savings contributes $600/month to a diversified index fund earning 7% annually. After 10 years the balance is $104,000; after 20 years $152,000 in contributions have grown to $313,000; after 40 years the portfolio reaches approximately $1,576,000. Total contributions over 40 years are $288,000 — meaning compound growth generated more than five times the contributed amount.

Scenario 2 — Mid-career catch-up with existing savings: A 40-year-old with $75,000 already saved increases monthly contributions to $1,500 and earns 7% annually. After 25 years (at age 65) the portfolio reaches about $1,635,000. The existing $75,000 grows to $407,000 on its own — illustrating that even a modest current balance provides a meaningful head start when time remains on your side.

Scenario 3 — Aggressive saver near retirement: A 50-year-old with $250,000 saved contributes $3,000/month and earns 6% annually. After 15 years the balance reaches approximately $1,503,000. Of that, $540,000 is total contributions and $713,000 is investment growth on top of the starting balance. This scenario shows that high contribution rates in the final 15 years before retirement can substantially close gaps for late starters.

Wealth Growth Reference Table

When to Use This Calculator

• You want to set a specific retirement savings target and work backward to determine the monthly contribution required to reach it given your current balance and expected return
• You are deciding between two job offers with different salaries and want to model how a $10,000 annual pay difference translates into long-term wealth if you invest the extra income
• You are evaluating whether to pay off a low-interest mortgage early or redirect that money to investments, and need to compare the compounded growth of investing versus the guaranteed debt savings
• You want to see how a 1% or 2% higher annual return affects your balance 20 years from now — the difference can be hundreds of thousands of dollars, making fee minimization highly visible
• You are setting age-based milestones (1x salary by 30, 3x by 40, etc.) and want to confirm your current trajectory will hit those markers given your savings rate

Common Mistakes

1. Using nominal return rates without adjusting for inflation. A portfolio growing at 8% nominally when inflation runs at 3% has a real return of about 5%. Project your wealth using 5-7% real returns to avoid overestimating future purchasing power — a $2 million nominal balance in 30 years may have the purchasing power of only about $820,000 in today’s dollars at 3% inflation.
2. Treating the projection as a guaranteed outcome. The compound growth formula assumes a steady annual return, but actual markets fluctuate. A sequence of poor returns early in retirement can deplete a portfolio much faster than the average return implies. Use the projection as a planning benchmark, not a promise.
3. Ignoring contribution increases over time. Most people earn more as their career progresses. Running the calculator with a flat $500/month contribution from age 25 to 65 understates realistic outcomes for someone who increases contributions from $500 to $2,000 between age 35 and 45. Re-run projections every few years with updated contribution amounts.
4. Conflating savings rate with contribution amount. A $1,000/month contribution means very different things on a $50,000 salary (24% rate) versus a $120,000 salary (10% rate). Research consistently shows that savings rate — the percentage of income saved, not the dollar amount — is the strongest predictor of whether someone achieves financial independence.

Wealth Growth in Context

The median U.S. household net worth is approximately $192,700 as of 2022 Federal Reserve data, but the average is skewed much higher by wealthy outliers. More actionable are age-cohort medians: roughly $39,000 for those under 35, $135,000 for ages 35-44, $247,000 for 45-54, and $364,000 for 55-64. If your balance trails these figures significantly, the calculator can help you quantify how quickly an aggressive savings increase can close the gap — because time is the one input you cannot buy back.

A commonly cited benchmark from Fidelity suggests having 1x your salary saved by 30, 3x by 40, 6x by 50, and 10x by 67. For a $75,000 earner those targets are $75,000, $225,000, $450,000, and $750,000. Run the calculator to see what monthly contribution rate achieves each milestone on schedule.

Tips

• Automate contributions so that a fixed percentage of every paycheck goes directly to your investment account before it reaches your checking account — behavioral research consistently shows that automatic saving is more effective than manual transfers
• Every time you receive a raise or bonus, route at least half of the after-tax increase into investments; this builds wealth faster than your previous trajectory while still allowing lifestyle improvement
• Model the impact of investment fees: a fund charging 0.9% annually versus one charging 0.04% annually costs roughly $200,000 more in fees on a $500,000 portfolio over 30 years at 7% growth
• Use a 5-6% real return assumption for stock-heavy portfolios rather than the 9-10% nominal historical average; this prevents overconfidence and keeps your target balance realistic in today’s purchasing power
• Check your net worth quarterly rather than monitoring daily account balances — it provides a cleaner view of trajectory and reduces the temptation to sell during short-term market drops
• Recalculate every two to three years as your income, expenses, and contribution capacity change; a projection built at 30 on a $50,000 salary needs updating at 40 when salary and savings rate have both grown