Token Quantity Conversion

You are referring to the Legacy version of KyberSwap docs.

For the most updated information, please refer to:

• Classic

• Elastic

• Limit Order

• Aggregator

Token Amount Conversion​

Since getExpectedRate returns a rate, not the amount, the following code snippets show how to convert to both source and destination token amounts, taking their decimals into account.

calcSrcQty​

Parameter	Description
dstQty	ERC20 destination token amount in its decimals
srcDecimals	ERC20 source token decimals
dstDecimals	ERC20 destination token decimals
rate	src -> dst conversion rate, independent of token decimals

Returns: ERC20 source token amount in its decimals.

Javascript​

// DISCLAIMER: Code snippets in this guide are just examples and you
// should always do your own testing. If you have questions, visit our
// https://t.me/KyberDeveloper.

function calcSrcQty(dstQty, srcDecimals, dstDecimals, rate) {
  const PRECISION = 10 ** 18;
  //source quantity is rounded up. to avoid dest quantity being too low.
  if (srcDecimals >= dstDecimals) {
    numerator = PRECISION * dstQty * 10 ** (srcDecimals - dstDecimals);
    denominator = rate;
  } else {
    numerator = PRECISION * dstQty;
    denominator = rate * 10 ** (dstDecimals - srcDecimals);
  }
  return (numerator + denominator - 1) / denominator; //avoid rounding down errors
}

Solidity​

Refer to the Utils contract.

calcDstQty​

Parameter	Description
srcQty	ERC20 source token amount in its decimals
srcDecimals	ERC20 source token decimals
dstDecimals	ERC20 destination token decimals
rate	src -> dst conversion rate, independent of token decimals

Returns: ERC20 destination token amount in its decimals.

Javascript​

// DISCLAIMER: Code snippets in this guide are just examples and you
// should always do your own testing. If you have questions, visit our
// https://t.me/KyberDeveloper.

function calcDstQty(srcQty, srcDecimals, dstDecimals, rate) {
  const PRECISION = 10 ** 18;
  if (dstDecimals >= srcDecimals) {
    return (srcQty * rate * 10 ** (dstDecimals - srcDecimals)) / PRECISION;
  } else {
    return (srcQty * rate) / (PRECISION * 10 ** (srcDecimals - dstDecimals));
  }
}

Solidity​

Refer to the Utils contract.

calcRateFromQty​

Parameter	Type	Description
srcAmount	Number	ERC20 source token amount in its decimals
destAmount	Number	ERC20 destination token amount in its decimals
srcDecimals	Number	ERC20 source token decimals
dstDecimals	Number	ERC20 destination token decimals

Returns: Token conversion rate independent of token decimals

Javascript​

// DISCLAIMER: Code snippets in this guide are just examples and you
// should always do your own testing. If you have questions, visit our
// https://t.me/KyberDeveloper.

function calcRateFromQty(srcAmount, destAmount, srcDecimals, dstDecimals) {
  const PRECISION = 10 ** 18;
  if (dstDecimals >= srcDecimals) {
    return (
      (destAmount * PRECISION) / (10 ** (dstDecimals - srcDecimals) * srcAmount)
    );
  } else {
    return (
      (destAmount * PRECISION * 10 ** (srcDecimals - dstDecimals)) / srcAmount
    );
  }
}

Solidity​

Refer to the Utils2 contract.