_title: Big Number _section: BigNumber @ Explain about BigNumber here... _heading: Importing _code: bignumber-import.source _subsection: Types _heading: BigNumberish @ Many functions and methods in this library take in values which can be non-ambiguously and safely converted to a BigNumber. These values can be sepcified as: _definition: **//string//** A [hexstring](hexstring) or a decimal string, either of which may be negative. _definition: **//BytesLike//** A [BytesLike](byteslike) Object, such as an Array or Uint8Array. _definition: **//BigNumber//** An existing BigNumber instance. _definition: **//number//** A number that is within the safe range for JavaScript numbers. _definition: **//BigInt//** A JavaScript [BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt) object, on environments that support BigInt. _subsection: Creating Instances The constructor of BigNumber cannot be called directly. Instead, Use the static ``BigNumber.from``. _property: BigNumber.from(aBigNumberish) => [[bignumber]] Returns an instance of a **BigNumber** for //aBigNumberish//. _heading: Examples: _code: bignumber-create.js _subsection: Methods The BigNumber class is immutable, so no operations can change the value it represents. _heading: Math Operations _property: bignumber.add(otherValue) => [[bignumber]] Returns a BigNumber with the value of //bignumber// **+** //otherValue//. _property: bignumber.sub(otherValue) => [[bignumber]] Returns a BigNumber with the value of //bignumber// **–** //otherValue//. _property: bignumber.mul(otherValue) => [[bignumber]] Returns a BigNumber with the value of //bignumber// **×** //otherValue//. _property: bignumber.div(divisor) => [[bignumber]] Returns a BigNumber with the value of //bignumber// **÷** //divisor//. _property: bignumber.mod(divisor) => [[bignumber]] Returns a BigNumber with the value of the **remainder** of //bignumber// ÷ //divisor//. _property: bignumber.pow(exponent) => [[bignumber]] Returns a BigNumber with the value of //bignumber// to the power of //exponent//. _property: bignumber.abs() => [[bignumber]] Returns a BigNumber with the absolute value of //bignumber//. _property: bignumber.maskn(bitcount) => [[bignumber]] Returns a BigNumber with the value of //bignumber// with bits beyond the //bitcount// least significant bits set to zero. _heading: Two's Compliment [Two's Complicment](https://en.wikipedia.org/wiki/Two%27s_complement) is a method used to encode and decode fixed-width values which can be positive or negative, without requiring a separate sign bit. Most users will not need to interact with these. _property: bignumber.fromTwos(bitwidth) => [[bignumber]] Returns a BigNumber with the value of //bignumber// converted from twos-compliment with //bitwidth//. _property: bignumber.toTwos(bitwidth) => [[bignumber]] Returns a BigNumber with the value of //bignumber// converted to twos-compliment with //bitwidth//. _heading: Comparison and Equivalence _property: bignumber.eq(otherValue) => boolean Returns true if and only if the value of //bignumber// is equal to //otherValue//. _property: bignumber.lt(otherValue) => boolean Returns true if and only if the value of //bignumber// **<** //otherValue//. _property: bignumber.lte(otherValue) => boolean Returns true if and only if the value of //bignumber// **≤** //otherValue//. _property: bignumber.gt(otherValue) => boolean Returns true if and only if the value of //bignumber// **>** //otherValue//. _property: bignumber.gte(otherValue) => boolean Returns true if and only if the value of //bignumber// **≥** //otherValue//. _property: bignumber.isZero() => boolean Returns true if and only if the value of //bignumber// is zero. _heading: Conversion _property: bignumber.toNumber() => number Returns the value of //bignumber// as a JavaScript value. This will **throw an error** if the value is greater than or equal to //Number.MAX_SAFE_INTEGER// or less than or equal to //Number.MIN_SAFE_INTEGER//. _property: bignumber.toString() => string Returns the value of //bignumber// as a base-10 string. _property: bignumber.toHexString() => string Returns the value of //bignumber// as a base-16, `0x`-prefixed [hexstring](hexstring). _heading: Inspection _property: BigNumnber.isBigNumber(object) => boolean Returns true if and only if the //object// is a BigNumber object. _heading: Examples _code: bignumber-examples.js _subsection: Notes A few short notes on numbers... _heading: Why can't I just use numbers? The first problem many encounter when dealing with Ethereum is the concept of numbers. Most common currencies are broken down with very little granularity. For example, there are only 100 cents in a single dollar. However, there are 10^^18^^ **wei** in a single **ether**. JavaScript uses [IEEE 754 double-precision binary floating point](https://en.wikipedia.org/wiki/Double-precision_floating-point_format) numbers to represent numeric values. As a result, there are //holes// in the integer set after 9,007,199,254,740,991; which is problematic for //Ethereum// because that is only around 0.009 ether (in wei), which means any value over that will begin to experience rounding errors. To demonstrate how this may be an issue in your code, consider: _code: bignumber-ieee754.js To remedy this, all numbers (which can be large) are stored and manipulated as [Big Numbers](bignumber). The functions [parseEther( etherString )](http://linkto) and [formatEther( wei )](http://linkto) can be used to convert between string representations, which are displayed to or entered by the user and Big Number representations which can have mathematical operations handled safely.