How much is $100,000 invested at 8% for 20 years worth?

$100,000 invested at 8% for 20 years grows to $492,680. You contributed $100,000 and earned $392,680 from compound growth — 80% of your final balance came from compounding alone.

Is 8% realistic for 20 years?

8% is moderate — typical of balanced stock/bond portfolios. S&P 500 long-run real return is ~7%. For most retirement planning, 7% is a reasonable middle estimate.

What if I change the rate?

Use the live calculator below — change the annual rate slider to see how a 1-percentage-point increase or decrease impacts your final balance over 20 years. The math: balance = $100,000 × (1 + r/12)^240.

Compound scenario · Verified 2026-07-02

$100,000 invested at 8% for 20 years

Grows to $492,680 over 20 years. You contribute $100,000; the remaining $392,680 (80%) comes from compound growth.

Final balance

$492,680

You contributed

$100,000

From compounding

$392,680

Live calculator (pre-filled with this scenario)

Change any input to explore variations. Or open this exact scenario in the full calculator.

Year-by-year breakdown

Year	Total contributed	Interest earned	Balance
1	$100,000	$8,300	$108,300
2	$100,000	$17,289	$117,289
3	$100,000	$27,024	$127,024
4	$100,000	$37,567	$137,567
5	$100,000	$48,985	$148,985
… 10 more years …
16	$100,000	$258,139	$358,139
17	$100,000	$287,865	$387,865
18	$100,000	$320,057	$420,057
19	$100,000	$354,922	$454,922
20	$100,000	$392,680	$492,680

How this number was calculated

Standard compound interest formula with monthly compounding (n = 12):

Balance = P × (1 + r/n)^(n × t)  +  PMT × [((1 + r/n)^(n × t) − 1) / (r/n)]

where:
  P   = $100,000        (initial amount)
  PMT = $0        (monthly contribution)
  r   = 0.0800            (annual rate as decimal)
  n   = 12                  (compounding periods per year)
  t   = 20                  (years)

Final balance = $492,680

Same closed-form math used by Investor.gov (SEC) and 7 other major calculators we tested — all produce identical results to the cent.

Related scenarios

$10,000 invested at 7% for 30 years

→ $81,165 (30 years at 7%)

$10,000 invested at 10% for 20 years

→ $73,281 (20 years at 10%)

$25,000 invested at 7% for 30 years

→ $202,912 (30 years at 7%)

$50,000 invested at 7% for 25 years

→ $286,271 (25 years at 7%)

Try other scenarios

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Educational tool. Past performance does not predict future returns. Verified 2026-07-02. Math validated against Robert Shiller's S&P 500 historical dataset.