@toolsnap/compound-interest-calculator

A lightweight, zero-dependency JavaScript library for calculating compound interest, monthly contribution growth, and effective annual rates.

Features

• 📈 Compound interest calculation with configurable frequency (annual, quarterly, monthly, daily)
• 💰 Monthly contribution support (annuity formula)
• 📊 Year-by-year growth schedule
• 🔢 Effective annual rate (EAR) computation
• 🪶 Zero dependencies
• ✅ Full input validation

Installation

npm install @toolsnap/compound-interest-calculator

Usage

Basic Compound Interest

const { compoundInterest } = require('@toolsnap/compound-interest-calculator');

const result = compoundInterest(10000, 0.06, 10, 12);
// {
//   principal: 10000,
//   totalInterest: 8193.97,
//   totalValue: 18193.97,
//   effectiveRate: 6.1678
// }

With Monthly Contributions

const { withMonthlyContribution } = require('@toolsnap/compound-interest-calculator');

const result = withMonthlyContribution(5000, 200, 0.07, 20);
// {
//   principal: 5000,
//   totalContributions: 53000,
//   totalInterest: 34664.42,
//   totalValue: 87664.42
// }

Effective Annual Rate

const { effectiveAnnualRate } = require('@toolsnap/compound-interest-calculator');

const ear = effectiveAnnualRate(0.05, 12);
// 0.05116... (~5.12%)

Year-by-Year Growth Schedule

const { growthSchedule } = require('@toolsnap/compound-interest-calculator');

const schedule = growthSchedule(10000, 500, 0.06, 5);
// [
//   { year: 1, deposit: 6000, interest: 648.42, balance: 16648.42 },
//   { year: 2, deposit: 6000, interest: 1030.56, balance: 23678.98 },
//   ...
// ]

API

compoundInterest(principal, rate, time, frequency)

Calculate compound interest on a principal amount.

| Parameter | Type | Description | |-------------|--------|------------------------------------------------| | principal | number | Initial investment amount | | rate | number | Annual interest rate (decimal, e.g. 0.05) | | time | number | Time period in years | | frequency | number | Compounding frequency/year (default: 12) |

withMonthlyContribution(principal, monthly, rate, years)

Calculate growth with regular monthly contributions using the annuity formula.

effectiveAnnualRate(nominalRate, frequency)

Convert a nominal rate to the effective annual rate (EAR).

growthSchedule(principal, monthly, rate, years)

Generate a year-by-year breakdown of deposits, interest earned, and balance.

Online Calculator

For a full-featured interactive calculator, visit:

👉 Compound Interest Calculator

Related tools:

• Investment Return Calculator
• Risetop - Free Online Tools

License

MIT © ToolSnap