# Adding a dimension with derived units in Unitful

**URL:** https://discourse.julialang.org/t/adding-a-dimension-with-derived-units-in-unitful/127476
**Category:** New to Julia
**Created:** [March 28, 2025, 11:39pm UTC](https://discourse.julialang.org/t/adding-a-dimension-with-derived-units-in-unitful/127476 "2025-03-28T23:39:29Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![mjmat](https://avatars.discourse-cdn.com/v4/letter/m/85f322/32.png) [@mjmat](https://discourse.julialang.org/u/mjmat)
#### Post date: [March 28, 2025, 11:39pm UTC](https://discourse.julialang.org/t/adding-a-dimension-with-derived-units-in-unitful/127476/1 "2025-03-28T23:39:29Z")

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Hello,  
I am trying to add a dimension to Unitful. I can do that, and I can create (and use) a refunit, but I can’t seem to be able to create derived units.  
In the code below, the commented line in the module (trying to create a bigthing) causes an error (ERROR: LoadError: ArgumentError: Symbol thing could not be found in unit modules Module[Unitful])

```julia
using Unitful
module MyUnits
    using Unitful
    @dimension Stuff "Stuff" TheStuff false
    @refunit thing "thing" thing Stuff true
    # @unit bigthing "bigthing" thebigthing 4u"thing" false
end
Unitful.register(MyUnits)
using .MyUnits
test = 1u"thing" |> u"kthing" # OK for predefined SI prefixes, but I would like a bigthing!

```

Could someone shed some light on what I am doing wrong?