# Convert decimal to hex and back after transformation
**URL:** https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280
**Category:** General
**Created:** [24 September 2020 10:52 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280 "2020-09-24T10:52:38Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@John245](https://discourse.nodered.org/u/John245)
#### Post date: [24 September 2020 10:52 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280/1 "2020-09-24T10:52:39Z")
I want to do the following.
msg.payload[8]=12
msg.payload[9]=39161
I want to convert msg.payload[8] and [9] to Hex numbers (respectively C and 98F9).
I have several issues.
1. how do I convert to Hex numbers
2. how do I convert from Hex to decimal. I tried
var HexNumber = 'C98F9';
msg.payload = parseInt(HexNumber);
return msg;
But that resulted in NaN
0xF will result in 15
I'm a newbie in Node-Red, any help is appreciated.
* * *
John
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [24 September 2020 11:05 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280/2 "2020-09-24T11:05:39Z")
When you say you want to convert it to a hex number, do you mean that you want a string containing "98f9"? If you are not sure what that means then tell us what do you want to do with the hex number.
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### Author:  [@John245](https://discourse.nodered.org/u/John245)
#### Post date: [24 September 2020 11:17 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280/3 "2020-09-24T11:17:07Z")
I want to convert both payloads to Hex and then combine both Hex numbers and convert to a decimal number
So If I can convert the payloads to Hex (resulting in C and 98FG) and combine these strings (resulting in C98FG) it is ok. After that the string containing the Hex number should be converted to a decimal value (end result 825593).
* * *
John
---
### Author:  [@Colin](https://discourse.nodered.org/u/Colin)
#### Post date: [24 September 2020 11:35 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280/4 "2020-09-24T11:35:56Z")
You don't need to convert it at all, just shift the first value left 16 bits and add on the second
```auto
msg.payload = (msg.payload[8] <<16) + (msg.payload[9] & 0xffff)
return msg
```
The and with 0xffff is to force it to an unsigned value, as, for example, if the second word was -1 it would actually mean 65535
---
### Author:  [@John245](https://discourse.nodered.org/u/John245)
#### Post date: [24 September 2020 12:21 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280/5 "2020-09-24T12:21:01Z")
Thanks a lot, this is much simpler as in C++.
* * *
John
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### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [23 November 2020 12:21 UTC](https://discourse.nodered.org/t/convert-decimal-to-hex-and-back-after-transformation/33280/6 "2020-11-23T12:21:05Z")
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