How do I remove decimals from a uint256

Asked Aug 13 '22 at 07:27

Active Aug 13 '22 at 08:04

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I am calculating a buyPrice that has a factor of 1.2 times the normal price.

To do this I get the token price and multiply it by 1200000000000000000 (18). It looks something like:

uint256 buyPrice = get18DecimalPrice() * 18DecimalBuyMultiplier;

This works, but it leaves me with a 36 decimal integer. I need it to be 18 decimals for further calculations. How can I slice off the last 18?

I am aware that when you divide a 36 decimal uint with an 18 decimal uint, the result is an 18 decimal uint. I'm just not sure what to do to achieve such a result in this case.

EDIT: Thanks to Paul Razvan Berg I started using PRBMath, which does not produce the same problem. I am still looking for an answer to the question as I am curious about how these math libraries handle the problem laid out in the question.

edited Aug 13 '22 at 08:04

asked Aug 13 '22 at 07:27

Pim Hakkert

2

You may need to use a fixed-point math library. See PRBMath. – Paul Razvan Berg Aug 13 '22 at 07:35
@PaulRazvanBerg This worked, thank you. I would still like to know how it is able to remove the last 18 decimals, or even if it approaches this method in another way. – Pim Hakkert Aug 13 '22 at 07:58
No worries. Reading the README of the PRBMath should automatically answer this question for you. But in short, the idea is that you divide by 1e18 after you make the multiplication. – Paul Razvan Berg Aug 13 '22 at 08:23

How do I remove decimals from a uint256

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