Gabriel Malenowitch

Compound Interest Calculator

Compound Interest

Simulate the growth of your investment and estimate monthly retirement income

Settings

R$

R$

%

Investment composition:
Accumulated interest
Monthly contributions
Initial deposit
Início
1
2
3
4
5
6
7
8
9
10
Breakdown at end of period:

Accumulated interest

R$ 42.473,44

26.1%

Monthly contributions

R$ 120.000,00

73.9%

Initial deposit

R$ 0,00

0.0%

Your final amount

R$ 162.473,44

Monthly retirement income
Moderate Withdrawal — 4% per year

R$ 541,58

Monthly income

Annual income: R$ 6.498,94

≈ 30-year estimated sustainability
Conservative Withdrawal — 3% per year

R$ 406,18

Monthly income

Annual income: R$ 4.874,20

≈ Long-term wealth preservation
Important

The 3% and 4% withdrawal rules are based on historical US market research: the Trinity Study (Cooley, Hubbard & Walz, 1998) and Bill Bengen's research (1994), which analyzed diversified stock and bond portfolios over decades. Other markets, including Brazil, have different characteristics — higher volatility, historically higher inflation, and shorter market history. Safe withdrawal rates may differ significantly. Use these estimates as a reference, not a guarantee.


Sources: Cooley, Hubbard & Walz — "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable" (1998) • Bill Bengen — "Determining Withdrawal Rates Using Historical Data" (1994)

Compound Interest Formula with Contributions

The final amount is calculated using the compound interest formula with periodic monthly contributions. The equivalent monthly rate is derived from the nominal annual rate.

M = P × (1 + i)ⁿ + C × [(1 + i)ⁿ − 1] / i
MFinal amount
PInitial deposit (principal)
iEquivalent monthly interest rate
nNumber of periods (months)
CMonthly contribution
Annual Rate References

Selic

Brazil's benchmark interest rate (Mar/2026 ≈ 13.75% p.a.)

IPCA+5%

Inflation + 5% real return (common Brazilian equity benchmark)

S&P 500

S&P 500 historical annual average in USD (~10% p.a.)

CDI

Very close to Selic; Brazilian fixed-income benchmark

Poupança

Minimum savings return (~6–7% p.a.); usually loses to inflation

Safe Withdrawal Rule

The 4% rule estimates how much you can withdraw annually without depleting your portfolio over 30 years. The 3% rule is more conservative and aims for indefinite sustainability. Both assume a diversified portfolio and historical US market returns.