I am new to testing and I want to know how to convert a big number to a real number.

I use bignumber in the following command:

console.log(await this.crowdsale.rate());

This is what gets printed in the terminal:

BigNumber { s: 1, e: 2, c: [ 500 ] }

2 Answers 2


It depends what you mean by real number. You can check out here the divisions used in Ethereum.

For wei:

let bigNo = await this.crowdsale.rate();

For ether add this:


If you're using version ^1.0.0 of web3, use web3.utils.fromWei instead of web3.fromWei.

  • 1
    thanks paul .i forgot about toNumber() thanks for reminding me about it .
    – AVATAR
    Commented Sep 25, 2018 at 15:20

Not every BigNumber can be converted into a Javascript Number with an equivalent value.

If that had been the case, then we wouldn't have needed a BigNumber class to begin with.

Referring to your actual question - you haven't really explained why you need to perform this conversion.

Your question implies that you don't like the printout, in which case you can fix your code as follows:

let rate = await this.crowdsale.rate();

If you're interested in performing additional calculations, then you can simply use BigNumber functions.

So technically speaking, there shouldn't be any need convert your BigNumber into a Javascript Number.

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