Capital.js

Installation

In a browser:

<script src="capital.js"></script>

Using npm:

$ npm install capitaljs

Usage

In a browser:

var rate = capitaljs.compoundAnnualGrowthRate({...});

In an AMD loader:

require(['capitaljs'], function(capitaljs) {...});

In Node:

var capitaljs = require('capitaljs');
var rate = capitaljs.compoundAnnualGrowthRate({...});

Or if you just want a single formula (to reduce your browser bundle's filesize):

var cagr = require('capitaljs/compoundAnnualGrowthRate');
var rate = cagr({...});

Current formulae

Amortization

Calculate the monthly payment of an amortizing loan (like a mortgage) and how the loan has amortized after a specified period of time.

Options

Option	Format	Details
amount	number	Total amount of the loan
rate	number	Annual interest rate of the loan
totalTerm	number	Total length of the loan, in months
amortizeTerm	number	Point in time after the start of the loan you’d like to check the amortization, in months

Returns

Property	Format	Details
balance	number	Total amount of principal left to be paid after the number of months specified in amortizeTerm
balanceRound	string	balance rounded to the nearest cent
interest	number	Total amount of interest paid on the loan after the number of months specified in amortizeTerm
interestRound	string	interest rounded to the nearest cent
payment	number	Monthly payment
paymentRound	string	payment rounded to the nearest cent
principal	number	Total amount of principal paid on the loan after the number of months specified in amortizeTerm
principalRound	string	principal rounded to the nearest cent

Example

var amortization = require('capitaljs/amortization');

// What’s the amortization like after 5 years for a 30-year, $180,000 mortgage
// with a 4.25% interest rate?
amortization( {
  amount: 180000,
  rate: 4.25,
  totalTerm: 360,
  amortizeTerm: 60
} );

/*
{
  balance: 163453.85387151438,
  balanceRound: "163453.85",
  interest: 36583.362108097754,
  interestRound: "36583.36",
  payment: 885.4918039430557,
  paymentRound: "885.49",
  principal: 16546.146128485594,
  principalRound: "16546.15"
}
*/

Cash flow

Calculate how much money is left after subtracting expenses from income.

Options

Option	Format	Details
income	positive number or array	Total income or an array with all sources of income
expenses	positive number or array	Total expenses or an array with all expenses

Returns

Property	Format	Details
cash	number	Total cash left over after subtracting expenses from income
expenses	number	Total expenses
income	number	Total income

Examples

var cashFlow = require('capitaljs/cashFlow');

// How much money is left over given $50,000 of expenses and a $100,000 income?
cashFlow( {
  income: 100000,
  expenses: 50000
} );

/*
{
  cash: 50000,
  expenses: 50000,
  income: 100000
}
*/

// How much money is left over given a bunch of different income sources and
// a bunch of different expenses?
cashFlow( {
  income: [300, 14000, 189],
  expenses: [90, 681, 15980, 670]
} );

/*
{
  cash: -2932,
  expenses: 17421,
  income: 14489
}
*/

Compound annual growth rate

Calculate a compounded annual rate of return on an investment.

Options

Option	Format	Details
startValue	number	Starting value of the investment
endValue	number	Ending value of the investment
years	number	Length of the investment, in years

Returns

Property	Format	Details
percent	number	Compound annual growth rate of the investment, as an unrounded percent
raw	number	Raw compound annual growth rate of the investment
rounded	number	Raw compound annual growth rate of the investment, rounded to the nearest thousandth

Example

var compoundAnnualGrowthRate = require('capitaljs/compoundAnnualGrowthRate');

// What’s the compound annual growth rate of an investment that started at
// $50,000 and grew to $100,000 in 10 years?
compoundAnnualGrowthRate( {
  startValue: 50000,
  endValue: 100000,
  years: 10
} );

/*
{
  percent: 7.199999999999999,
  raw: 0.07177346253629313,
  rounded: 0.072
}
*/

Inflation-adjusted return

Calculate the return on an investment, accounting for inflation over the lifetime of the investment.

Options

Option	Format	Details
investmentReturn	number	Investment’s lifetime return, as a decimal (so “8%” is ".06")
inflationRate	number	Inflation rate over the lifetime of the investment, as a decimal (so “3%” is “.03”)

Returns

A single number, the inflation-adjusted return, as a percent rounded to the nearest hundredth

Example

var inflationAdjustedReturn = require('capitaljs/inflationAdjustedReturn');

// Adjusting for a 3% inflation rate, what’s the return for an investment that
// grew by 8%?
inflationAdjustedReturn( {
  investmentReturn: .08,
  inflationRate: .03
} );

// 4.85

Interest accrued

Calculate how much interest has been earned on an initial investment after a period of time.

Options

Option	Format	Details
principal	number	Initial amount invested
rate	number	Periodic interest rate, as a percent
periods	number	Years since the investment was started
compoundings	number	How often the interest rate is compounded per year (12 would be monthly, 4 is quarterly, 1 is yearly)

Returns

Property	Format	Details
interest	number	Total interest earned on the investment
total	number	Total current value of the investment, rounded to the nearest cent

Examples

var interest = require('capitaljs/interest');

// What’s a $10,000 investment with a 6% interest rate that compounds yearly
// worth after 10 years
interest( {
  principal: 10000,
  rate: 6,
  periods: 10,
  compoundings: 1
} );

/*
{
  interest: 7908.48,
  total: 17908.48
}
*/

// What’s a $10,000 investment with a 6% interest rate that compounds monthly
// worth after 10 years
interest( {
  principal: 10000,
  rate: 6,
  periods: 10,
  compoundings: 12
} );

/*
{
  interest: 8193.970000000001,
  total: 18193.97
}
*/

Return on investment

Calculate the return on an investment.

Options

Option	Format	Details
earnings	number	Final value of the investment
initialInvestment	number	Initial value of the investment

Returns

Property	Format	Details
percent	number	Return on investment, as an unrounded percent
raw	number	Raw return on investment
rounded	number	Raw return on investment, rounded to the nearest ten thousandth

Example

var returnOnInvestment = require('capitaljs/returnOnInvestment');

// What’s the return on a $70,000 investment that grew to $89,700?
returnOnInvestment( {
  earnings: 89700,
  initialInvestment: 70000
} );

/*
{
  percent: 28.139999999999997,
  raw: 0.2814285714285714,
  rounded: 0.2814
}
*/

Contributing

Please read the Contributing guidelines.

Running Tests

$ npm test

License

The project is in the public domain within the United States, and copyright and related rights in the work worldwide are waived through the CC0 1.0 Universal public domain dedication.

All contributions to this project will be released under the CC0 dedication. By submitting a pull request, you are agreeing to comply with this waiver of copyright interest.

Software source code previously released under an open source license and then modified by CFPB staff is considered a "joint work" (see 17 USC § 101); it is partially copyrighted, partially public domain, and as a whole is protected by the copyrights of the non-government authors and must be released according to the terms of the original open-source license.

For further details, please see: http://www.consumerfinance.gov/developers/sourcecodepolicy/