Fuel TS SDK

⌘K

Unit Conversion

Icon LinkUnit conversion

Internally, we use Arbitrary-precision Icon Link arithmetic (also known as Big Number arithmetic) to allow for the handling of large numbers and different assets.

On the Fuel network, we work with 9 decimals to represent amounts under a unit. This differs from chain to chain, so it is important to know the number of decimals used on the chain you are working with.

Icon InfoCircle
Note: The package @fuels/assets Icon Link provides a list of assets and their decimals.

Below we will go over some common use cases for unit conversion.

Using our BN class we can instantiate these numbers.

const myBigNumberOne = '100000000';
 
const resultOne = new BN('100000000').toString();

Or using our bn utility function.

 
const resultTwo = bn('100000000').toString();

Icon LinkContract calls

Generally, we will need to convert u64 and u256 numbers to a BN object when passing them to a Sway program from JavaScript. More information on this can be found here .

 
// Let's deploy a contract that has a function that takes a u64 as input
const provider = await Provider.create(LOCAL_NETWORK_URL);
 
const wallet = await Wallet.fromPrivateKey(WALLET_PVT_KEY, provider);
 
const deployedContract = await new EchoValuesFactory(wallet).deploy();
const { contract } = await deployedContract.waitForResult();
 
const MAX_U64 = bn('18446744073709551615');
 
const { waitForResult } = await contract.functions.echo_u64(MAX_U64).call();
const { value } = await waitForResult();

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Note: If a contract call returns a number that is too large to be represented as a JavaScript number, you can convert it to a string using the toString method instead of toNumber.

Icon LinkParsing

Parsing string-represented numbers (from user input) has never been easier, than using the parseUnits function.

const resultThree = bn.parseUnits('0.000000001').toString();

We can parse large numbers.

const myBigNumberFour = '100100000000000';
const resultFour = bn.parseUnits('100100').toString();

Or numbers formatted for human readability.

const myBigNumberFive = '100100000200001';
 
const resultFive = bn.parseUnits('100,100.000200001').toString();

We can also parse numbers in other units of measure.

const myBigNumberSix = '1000000000';
 
const resultSix = bn.parseUnits('1', DECIMAL_GWEI).toString();

Icon LinkFormatting

We can format common units of measure using the format function.

In the following example, we format a BigNumber representation of one Gwei, into units for the Fuel network (with 3 decimal place precision).

const myBigNumberSeven = '1.000';
const oneGwei = bn('1000000000');
 
const resultSeven = oneGwei.format();

We can also format numbers in other units of measure by specifying the units variable.

const myBigNumberEight = '2.000';
 
const twoGwei = bn('2000000000');
 
const resultEight = twoGwei.format({ units: DECIMAL_GWEI });

A precision variable will allow for the formatting of numbers with a specific number of decimal places.

const oneDecimalGwei = '1.0';
 
const formattedGwei = oneGwei.format({ precision: 1 });

Icon LinkFormat units

The formatUnits function is a lesser alternative to the format function, as it will maintain the same precision as the input value.

const myFormattedGwei = '1.000000000';
 
const formattedUnitsGwei = oneGwei.formatUnits();

We can also format numbers in other units of measure by specifying the units variable.

const myFormattedKwei = '1.000000000000000';
 
const oneKwei = bn('1000000000000000');
 
const formattedUnitsKwei = oneKwei.formatUnits(DECIMAL_KWEI);

Icon LinkSee also

Sway Numbers

Icon LinkFull Example

For the full example of unit conversion see the snippet below:

import { BN, DECIMAL_GWEI, DECIMAL_KWEI, bn, Provider, Wallet } from 'fuels';
 
import { LOCAL_NETWORK_URL, WALLET_PVT_KEY } from '../../../env';
import { EchoValuesFactory } from '../../../typegend/contracts/EchoValuesFactory';
 
const myBigNumberOne = '100000000';
 
const resultOne = new BN('100000000').toString();
 
 
const myBigNumberTwo = '100000000';
 
 
const resultTwo = bn('100000000').toString();
 
 
// Let's deploy a contract that has a function that takes a u64 as input
const provider = await Provider.create(LOCAL_NETWORK_URL);
 
const wallet = await Wallet.fromPrivateKey(WALLET_PVT_KEY, provider);
 
const deployedContract = await new EchoValuesFactory(wallet).deploy();
const { contract } = await deployedContract.waitForResult();
 
const MAX_U64 = bn('18446744073709551615');
 
const { waitForResult } = await contract.functions.echo_u64(MAX_U64).call();
const { value } = await waitForResult();
 
 
const myBigNumberThree = '1';
 
const resultThree = bn.parseUnits('0.000000001').toString();
 
 
const myBigNumberFour = '100100000000000';
const resultFour = bn.parseUnits('100100').toString();
 
 
const myBigNumberFive = '100100000200001';
 
const resultFive = bn.parseUnits('100,100.000200001').toString();
 
 
const myBigNumberSix = '1000000000';
 
const resultSix = bn.parseUnits('1', DECIMAL_GWEI).toString();
 
const myBigNumberSeven = '1.000';
const oneGwei = bn('1000000000');
 
const resultSeven = oneGwei.format();
 
const myBigNumberEight = '2.000';
 
const twoGwei = bn('2000000000');
 
const resultEight = twoGwei.format({ units: DECIMAL_GWEI });
 
const oneDecimalGwei = '1.0';
 
const formattedGwei = oneGwei.format({ precision: 1 });
 
const myFormattedGwei = '1.000000000';
 
const formattedUnitsGwei = oneGwei.formatUnits();
 
const myFormattedKwei = '1.000000000000000';
 
const oneKwei = bn('1000000000000000');
 
const formattedUnitsKwei = oneKwei.formatUnits(DECIMAL_KWEI);