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Finance

Free Compound Interest Calculator

Simulate your investments with monthly contributions and discover how much your money can grow over time. Instant results with interactive charts.

Simulation Data

Fill in the fields to calculate

$

Initial amount invested

$

Fixed monthly deposit

% p.y.

E.g. 10 = 10% per year

years

Period in whole years

💡

Quick Tip

Even small monthly contributions make a big difference long-term. Bump the monthly contribution by $50 and see the impact!

📊

Waiting for input

Fill in the fields on the left and click "Calculate" to see the results with interactive charts.

How the Compound Interest Formula Works

Understand the algorithm behind the simulation

Full Formula

M=C⋅(1+i)t+A⋅(1+i)t−1iM = C \cdot (1 + i)^{t} + A \cdot \frac{(1 + i)^{t} - 1}{i}
MFinal Amount
CInitial Capital
iRate per Period
t# of Periods
AMonthly Contribution

🧮 Step-by-step Example

1
Initial capital:$10,000

Amount invested upfront

2
Monthly contribution:$500

Fixed monthly deposit

3
Annual rate:6% p.y. (0.5% p.m.)

Investment yield

4
Term:5 years (60 months)

Investment period

📈 Calculated Result

After 5 years, the approximate amount would be $55,609.72, with $40,000.00 invested and $15,609.72 of compound interest generated.

💡 Key Concepts

Simple vs. Compound Interest

Simple interest applies only to the initial capital. Compound interest applies to capital + accrued interest — producing exponential growth.

The Snowball Effect

The longer money is invested, the bigger the impact. The later years of an investment yield far more than the early ones thanks to continuous reinvestment.

Regular Contributions

Each new contribution starts earning compound interest from the month it's made. The discipline of contributing monthly enormously boosts the end result.

Nominal vs. Real Rate

The nominal rate ignores inflation. To compare investments accurately, compute the real rate: ((1 + nominal) / (1 + inflation)) - 1.

Frequently Asked Questions

Common questions about compound interest

Compound interest is calculated on the principal plus already-accrued interest from previous periods — the famous "interest on interest". This makes your money grow exponentially over time, unlike simple interest which only applies to the initial capital.

Simple interest applies only to the initial capital across all periods. Compound interest adds each period's interest to the capital, and in the next period interest is calculated on this new value — producing exponential acceleration.

The formula is: M = C × (1 + i)^t + A × ((1 + i)^t − 1) / i. Where M = final amount, C = initial capital, i = monthly rate, t = number of months and A = monthly contribution. Our calculator does this automatically.

Depends on risk profile and term. Different products (savings, bonds, funds) offer different yields. Generally, the longer the term and the higher the risk, the higher the potential return. Use our calculator to simulate different scenarios.

Yes, a lot! Regular monthly contributions hugely amplify the compounding effect. Each new contribution starts compounding immediately. Consistency beats contribution size in importance.

Yes! calc/based offers all calculators 100% free, with no signup, login or payment. Our mission is to democratize access to quality financial tools.