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FINANCE & BUDGETING

Compound Interest Calculator

Calculate compound interest growth for savings and investments with recurring contributions, nominal or effective rates, a growth chart, and cumulative yearly balance tables.

Tool statusRuns in your browser
Preview
prontouso://finance/compound-interest01. PLAN → 02. RESULT → 03. GROWTH
01. PLAN
02. RESULT
03. GROWTH

Build the scenario

What matters comes first. Technical conventions stay explicit.

INPUT
R$
R$
From 1 month to 1,000 years. Decimals are rounded to the nearest month.
Changes the display unit only; no currency conversion is performed.
What does the rate you typed mean?
Effective annual: 8% represents a full year's growth. The compounding frequency doesn't matter here.
Quick scenarios

Simulation result

Final balance split between what you put in and what grew.

LIVE
ESTIMATED FINAL VALUE8% EFFECTIVE / YEAR
R$111,651.39
You will have put in R$70,000.00. The R$41,651.39 difference comes from compound growth under these assumptions.
120 MONTHS37.3% OF BALANCE = GROWTH
R$70,000.00TOTAL CONTRIBUTED
R$41,651.39INTEREST / GROWTH
8%EFFECTIVE ANNUAL RATE
0.6434%EQUIVALENT MONTHLY RATE
Wealth over timeCONTRIBUTIONS × BALANCE
total contributedbalance
Year by yearBREAKDOWN
PeriodContributedInterestBalance
1 yearR$16,000.00R$1,016.94R$17,016.94
2 yearsR$22,000.00R$2,595.24R$24,595.24
3 yearsR$28,000.00R$4,779.80R$32,779.80
4 yearsR$34,000.00R$7,619.13R$41,619.13
5 yearsR$40,000.00R$11,165.61R$51,165.61
6 yearsR$46,000.00R$15,475.80R$61,475.80
7 yearsR$52,000.00R$20,610.80R$72,610.80
8 yearsR$58,000.00R$26,636.61R$84,636.61
9 yearsR$64,000.00R$33,624.48R$97,624.48
10 yearsR$70,000.00R$41,651.39R$111,651.39
Assumptions usedNO BLACK BOX
annual rate used = effective rate entered
equivalent monthly rate = (1 + effective annual rate)^(1/12) − 1
contribution = end of month
months = round(years × 12)

final balance = R$111,651.39
total contributed = R$70,000.00
growth = R$41,651.39

How it works

  1. Enter your input

    Fill in the values, paste your text, or upload the file this tool works with.

  2. See results instantly

    Most tools update live as you type; a few use a single button. Either way, the result appears right on this page.

  3. Use your results

    Copy, download, or share what the tool produces — you're always in control of the output.

Privacy and processing — Runs locally in your browser. This tool does not upload your input.

What is Compound Interest Calculator?

The Compound Interest Calculator projects savings or investment growth with an initial amount, monthly contributions, an annual rate, and a period. It separates contributions from growth and provides a chart and cumulative yearly breakdown.

UNDERSTAND THE TOOL

How to calculate compound interest with monthly contributions

Learn how compounding affects a balance over time, how recurring deposits change the projection, and how to read the cumulative yearly table.

The power of compound interest and exponential growth

Unlike simple interest, which only accrues on the initial principal, compound interest generates earnings on both the original capital and accumulated past interest, creating the snowball effect.

The balance shown by the calculator depends on the initial amount, recurring contribution, rate, period, and contribution timing. The result is a deterministic projection under those constant assumptions, not a return forecast.

Recurring monthly contributions and deposit timing

Recurring contributions increase the amount added to the simulated balance. Depositing at the beginning of each month lets each new contribution participate in that month's growth.

Depositing at the end of each month adds the contribution after that month's growth. The difference between the two modes depends on the rate, contribution, and period entered.

Nominal vs effective rates and compounding frequencies

A nominal annual rate compounded more frequently (such as monthly, quarterly, or daily) yields a higher effective annual return due to earlier reinvestment of interest earnings.

In nominal mode, the simulator converts the entered nominal annual rate and selected compounding frequency into an effective annual rate, then derives its equivalent monthly rate. In effective mode, the entered annual rate is used directly.

Interpreting charts, yearly breakdown tables, and multiplier metrics

The output panel breaks down your final portfolio value into two core pillars: out-of-pocket contributions versus pure compound interest gains.

The cumulative table shows total contributions, accumulated growth, and balance at each completed year, plus a final partial-year row when needed. It does not report each year's standalone return.

Future Value with End-of-Month Deposits
FV = P * (1 + r)^n + PMT * [((1 + r)^n - 1) / r]
Equivalent Monthly Rate
r_monthly = (1 + r_annual)^(1 / 12) - 1

Example: 10-Year investment projection

Starting with $10,000 and contributing $500/month at 10% annual return for 10 years:

Initial Principal: $10,000.00 Monthly Deposit: $500.00 for 10 years (120 months) Total Invested: $70,000.00 Compound Interest Earned: $55,869.35 Final Balance: $125,869.35 (Interest accounts for 44.4% of the balance)

Local calculations in your browser

The amounts and rates entered in this calculator are processed in your browser to build the projection, chart, and table. This tool does not upload or store those values on a server.

Frequently Asked Questions

What period can I simulate?

You can enter a period from 1 month to 1,000 years. Decimal years are converted to months and rounded to the nearest month before the simulation runs.

How does compounding frequency impact the final balance?

Compounding frequency is used only when you choose a nominal annual rate. A higher frequency changes the effective annual rate derived from that nominal rate; an effective annual rate already includes compounding effects.

Does depositing at the beginning of the month make a noticeable difference?

A contribution made at the start of the month participates in that month's growth, while an end-of-month contribution does not. The resulting difference depends on the values and period entered.

Does the calculator account for taxes and inflation?

Taxes and fees are not deducted. The optional purchasing-power setting deflates the final nominal balance using the constant inflation rate you enter; it is an illustration, not an inflation forecast.

Does changing the currency convert the amounts?

No. The currency selector changes only the symbol and number formatting shown with the existing values. It does not apply an exchange rate.

Is my personal financial data stored on your servers?

No. The values entered in this calculator are processed locally in your browser and are not uploaded or stored by the tool.

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