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Token Quantity Conversion

{% hint style="warning" %} You are referring to the Legacy version of KyberSwap docs.

For the most updated information, please refer to:

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.