# Unitful quantities of something
**URL:** https://discourse.julialang.org/t/unitful-quantities-of-something/101978
**Category:** General Usage
**Tags:** unitful
**Created:** [July 23, 2023, 7:19pm UTC](https://discourse.julialang.org/t/unitful-quantities-of-something/101978 "2023-07-23T19:19:44Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@jar1](https://discourse.julialang.org/u/jar1)
#### Post date: [July 23, 2023, 7:19pm UTC](https://discourse.julialang.org/t/unitful-quantities-of-something/101978/1 "2023-07-23T19:19:44Z")
Say I want to represent concentrations like “milligrams of salt per milligrams of sugar”. Unitful.jl doesn’t seem to support this:
```julia
julia> typeof(3u"mg"/100u"mg")
Float64
```
What would you suggest?
---
### Author:  [@gdalle](https://discourse.julialang.org/u/gdalle)
#### Post date: [July 23, 2023, 7:30pm UTC](https://discourse.julialang.org/t/unitful-quantities-of-something/101978/2 "2023-07-23T19:30:46Z")
maybe [Defining new units · Unitful.jl](https://painterqubits.github.io/Unitful.jl/stable/newunits/) ?
---
### Author:  [@jar1](https://discourse.julialang.org/u/jar1)
#### Post date: [July 23, 2023, 7:46pm UTC](https://discourse.julialang.org/t/unitful-quantities-of-something/101978/3 "2023-07-23T19:46:59Z")
Following that example I can get
```julia
julia> 3u"myMeter" / 2u"m"
1.5 m m^-1
julia> 3u"myMeter" / 2u"m" |> typeof
Quantity{Float64, NoDims, Unitful.FreeUnits{(m^-1, m), NoDims, nothing}}
julia> 3u"myMeter" / 2u"m" == 3u"m" / 2u"myMeter"
true
```
which is better than nothing but doesn’t really distinguish between the two quantities.
---
### Author:  [@bertschi](https://discourse.julialang.org/u/bertschi)
#### Post date: [July 24, 2023, 5:14pm UTC](https://discourse.julialang.org/t/unitful-quantities-of-something/101978/4 "2023-07-24T17:14:22Z")
Guess, in order to distinguish between such quantities you need to make them different `Dimensions`. In the example, you are just defining a different unit of measurement, i.e., `myMeter`, with a corresponding conversion factor into the standard unit of measurement `m`. It still applies to the same physical quantity/dimension and thus \frac{3 \; \mathrm{myMeter}}{2 m} is a unitless quantity.
Not sure what the proper physical quantity for `salt per sugar` would/should be? Maybe better to use standard concentration or mass units and separately track to which substances these apply?
---
### Author:  [@briochemc](https://discourse.julialang.org/u/briochemc)
#### Post date: [September 19, 2023, 2:02pm UTC](https://discourse.julialang.org/t/unitful-quantities-of-something/101978/5 "2023-09-19T14:02:33Z")
A bit late to the party but maybe @Raf’s [UnitfulMoles.jl](https://github.com/rafaqz/UnitfulMoles.jl) is helpful?
AFAIK, you can work with custom moles, as below (copy-pasted from the ReadMe):
```julia
julia> using UnitfulMoles, Unitful
julia> @mol A
molA
julia> @mol B
molB
julia> 0.5molA/molB
0.5 molA molB⁻¹
```
but you can’t do the same for other units, like grams. You can maybe create your own package called UnitfulGrams.jl that just replaces UnitfulMoles.jl’s moles for grams? 🤷♂️