Investment Calculator
Project lump-sum + monthly contributions with inflation, step-ups, and a real DCA vs lump-sum comparison.
Investment Plan
Final balance
$345.7K
$345,742
You contributed
$130.0K
over 20 years
Investment growth
$215.7K
compound returns
Real value (today's $)
$191.4K
adjusted for 3% inflation
Growth Over Time
Lump Sum vs DCA Comparison
Same total ($130.0K) invested as lump sum on day one vs spread monthly:
Historically lump sum beats DCA ~70% of the time, but DCA hedges against bad market timing.
About this tool
A complete investment growth calculator. Combine an initial lump sum with monthly contributions, set an expected return, and see your projected balance year by year. Built-in inflation adjustment shows you the real purchasing power of your future balance, and an annual step-up models the contribution increases that come with raises.
How to use it
Quick steps to get the most out of this utility.
- 1
Enter your starting amount
Initial lump sum and monthly contribution.
- 2
Set the timeline and return
Years to invest and expected annual return (7–8% is realistic for stock-heavy portfolios).
- 3
Add inflation and step-up
Inflation shows real value; step-up grows monthly contributions each year.
- 4
Compare strategies
See lump sum vs DCA at the bottom — same total invested, very different outcomes.
Real returns are what matters
A nominal balance of $2 million in 30 years sounds amazing — until you realize that with 3% inflation, it has the purchasing power of about $824,000 in today's dollars. The "Real value" card on this calculator shows the inflation-adjusted balance, which is the only number that matters for retirement planning.
Why step-ups matter
Most people contribute a fixed dollar amount and never increase it. But your raises grow with inflation and career progression. Stepping up your contribution by 3–5% annually roughly doubles your final balance over 30 years compared to flat contributions, because you save more in your highest-earning years (when it compounds more aggressively).
Frequently asked questions
What is a realistic long-term return for stocks?+
The S&P 500 has averaged around 10% annual nominal return (7% real, after inflation) since 1957. For planning, assume 7% real return — anything higher is overly optimistic and risks under-saving.
Is lump sum or DCA better?+
Historically, lump sum beats dollar-cost averaging about 70% of the time because the market trends up over long periods, so getting money invested sooner means more compounding. DCA is better when you fear bad timing — it smooths volatility but accepts a lower expected return.
How does inflation affect my returns?+
Inflation reduces the purchasing power of your future balance. A 7% nominal return with 3% inflation gives a 4% real return. The "Real value" card on this calculator shows what your future balance is worth in today's dollars.
What is a step-up contribution?+
A step-up means increasing your monthly contribution each year, typically matching salary growth. A 3% annual step-up roughly doubles your final balance over 30 years compared to flat contributions, since you contribute more in your higher-earning years.
Why is compound growth so powerful?+
Compounding earns returns on prior returns. $1,000 invested at 8% becomes $4,661 in 20 years (4.7×) but $46,901 in 50 years (47×). The first 20 years feel slow; the last 20 years grow exponentially. This is why starting early matters so much.
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