Calculadora de Juros Compostos Grátis
Veja exatamente como seu dinheiro cresce com o poder dos juros compostos.
Compound interest is interest calculated on both the initial principal and all previously accumulated interest, described by the formula A = P(1 + r/n)^(nt). The S&P 500 has delivered an average annual return of approximately 10.3% before inflation and roughly 7% after inflation over the past 50 years (Damodaran, NYU Stern, 'Historical Returns on Stocks, Bonds and Bills,' 2025, https://pages.stern.nyu.edu/~adamodar/New_Home_Page/datafile/histretSP.html). CalcMyCompound models this growth instantly with adjustable inputs for principal, contributions, rate, compounding frequency, and time.
Como Usar Esta Calculadora
- 1
Insira seu valor inicial — a quantia disponível para investir hoje.
- 2
Defina seu aporte mensal — o valor que planeja adicionar todo mês.
- 3
Escolha o retorno anual esperado — 7% é uma estimativa conservadora comum.
- 4
Selecione a frequência de capitalização — mensal é a mais comum.
- 5
Ajuste o horizonte temporal — deslize até o número de anos desejado.
O Que São Juros Compostos?
Juros compostos são juros calculados tanto sobre o capital inicial quanto sobre os juros acumulados de períodos anteriores.
A Fórmula
A = P(1 + r/n)^(nt)Onde:
- A = Montante final
- P = Capital (investimento inicial)
- r = Taxa de juros anual (decimal)
- n = Número de capitalizações por ano
- t = Número de anos
Exemplo Rápido
Invista R$10.000 a 7% de juros anuais capitalizados mensalmente por 10 anos. Sem adicionar nenhum centavo, seu investimento cresce para R$20.097.
Written by Kymata Labs Editorial Team·Finance Tools Division
Reviewed by Kymata Labs QA·Technical Review
Simple Interest vs Compound Interest
The chart below shows how $10,000 grows over 20 years at 7% annual return. With simple interest, you earn a flat $700 each year. With compound interest, your earnings accelerate as interest earns interest — resulting in $24,719 more by year 20.
After 20 years at 7%, compound interest earns $24,719 more than simple interest on the same $10,000 investment.
Read our full guide: Compound vs Simple Interest — What's the Difference?
The Rule of 72
A quick mental math shortcut to estimate how long it takes for an investment to double:
Years to double = 72 ÷ interest rateAt 8% annual returns: 72 ÷ 8 = 9 years to double your money.
Read our full guide: The Rule of 72 Explained
Understanding the Compound Interest Formula Step by Step
The compound interest formula A = P(1 + r/n)^(nt) calculates the future value of an investment by applying the interest rate repeatedly over compounding periods. Here is a worked example: $5,000 principal, 6% annual rate, monthly compounding, 15 years.
Given: $5,000 principal | 6% annual rate | Monthly compounding | 15 years
- 1Convert annual rate to periodic rate:
r/n = 0.06 ÷ 12 = 0.005 (0.5% per month) - 2Calculate total compounding periods:
n × t = 12 × 15 = 180 periods - 3Calculate the growth factor:
(1 + 0.005)^180 = 2.4541 - 4Multiply by principal:
$5,000 × 2.4541 = $12,270.47
Your $5,000 grows to $12,270.47 — a gain of $7,270.47 purely from compound interest, without adding a single dollar in contributions. CalcMyCompound performs this calculation instantly with any values you enter.
Common Investing Questions
How much money do I need to invest monthly to become a millionaire?
To reach $1,000,000 with compound interest at a 7% annual return compounded monthly, a 25-year-old needs to invest approximately $381 per month for 40 years, while a 35-year-old needs approximately $820 per month for 30 years (Vanguard, 'Principles for Investing Success,' 2024, https://investor.vanguard.com/investor-resources-education/investment-principles). CalcMyCompound models these exact scenarios — adjust the monthly contribution slider and time horizon to see your personalized projection.
Does compounding daily instead of monthly make a big difference?
Daily compounding produces marginally higher returns than monthly compounding, but the difference is small in practice. On a $10,000 investment at 7% over 30 years, daily compounding yields $81,165 versus $81,007 for monthly compounding — a difference of only $158 or 0.19%. The real drivers of growth are contribution amount, rate of return, and time horizon, not compounding frequency.
What is the average annual return of the stock market after inflation?
The S&P 500 has delivered an average inflation-adjusted annual return of approximately 7% over the past 50 years, compared to approximately 10.3% in nominal terms before inflation (Damodaran, NYU Stern, 'Historical Returns on Stocks, Bonds and Bills,' 2025, https://pages.stern.nyu.edu/~adamodar/New_Home_Page/datafile/histretSP.html). This 7% real return is the most commonly used conservative estimate for long-term investment projections and is the default rate many financial planners recommend.