Token Quantity Conversion

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​

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​

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​

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.

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