@gibme/finance

A simple collection of financial equations for Node.js and the browser.

Documentation

https://gibme-npm.github.io/finance/

Requirements

• Node.js >= 22

Installation

npm install @gibme/finance
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yarn add @gibme/finance
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Features

Amortization

• Payment - Calculate monthly payment breakdown (principal, interest, balance)
• Table - Generate a full amortization schedule with optional extra payment support
• Loan Information - Summarize total interest, savings from extra payments, and effective rates
• Principal from Payment - Reverse-calculate the loan principal given a known payment amount

Interest

• Annual Percentage Yield (APY) - Convert a nominal rate to its effective annual yield given a compounding period
• Compound Interest - Calculate the future value of a principal using the compound interest formula
• Simple Interest - Calculate the future value of a principal using the simple interest formula
• Simple Interest Loan - Summarize payment, total interest, and effective rate for a simple interest loan

Pricing

• Margin - Calculate the margin on a product given cost and selling price
• Markup - Calculate the markup on a product given cost and selling price

Valuation

• Present Value from Future Value - Discount a future value back to its present value at a constant rate

Moving Averages

• SMA - Simple Moving Average
• EMA - Exponential Moving Average
• LWMA - Linearly Weighted Moving Average
• EWMA - Exponentially Weighted Moving Average
• CMA - Cumulative Moving Average

Usage

import {
    calculate_amortization_loan,
    calculate_compound_interest,
    calculate_apy,
    calculate_sma
} from '@gibme/finance';

// 30-year mortgage at 6% with $200 extra/month starting month 1
const loan = calculate_amortization_loan(200000, 0.06, 360, [
    { month: 1, amount: 200, fill: true }
]);
console.log(loan.payment);        // monthly payment
console.log(loan.months_saved);    // months saved by extra payments
console.log(loan.interest_saved);  // interest saved by extra payments

// Compound interest: $10,000 at 5% compounded monthly for 5 years
const futureValue = calculate_compound_interest(10000, 0.05, 'monthly', 60);
console.log(futureValue);

// APY for 5% compounded daily
const apy = calculate_apy(0.05, 'daily');
console.log(apy);

// Simple moving average with a 3-period window
const sma = calculate_sma([10, 20, 30, 40, 50], 3);
console.log(sma); // [20, 30, 40]
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Compounding Periods

The following compounding periods are supported wherever a CompoundPeriod is accepted:

daily | weekly | biweekly | semimonthly | monthly | bimonthly | quarterly | semiannually | annually | biannually

APR Handling

Functions that accept an apr parameter will automatically convert values greater than 1 to a decimal (e.g. 5 becomes 0.05). You can pass either form.

License

MIT