Missing SI derived unit for Force per Length (kN/m, N/m) in Mathcad Prime 12

Question

I recently started using Mathcad Prime 12 for structural engineering / Eurocode calculations and I noticed something frustrating regarding the unit system.

Mathcad correctly understands that: kg/s² = N/m. However when working with line loads (common in structural engineering), Prime often displays results as “kg/s²” instead of the expected engineering SI unit: N/m or kN/m.

The strange part is that under “Insert Derived Units → Force per Length” there are several imperial units available: kpi, klf, plf. but there is NO SI alternative such as N/m or kN/m.

This creates a awkward workflow in SI-based calculations, especially for Eurocode and structural design where line loads are constantly used.

Currently the only workaround that i found seems to be manually dividing by (kN/m) , creating display variables or manually writing the unit as text. This partly defeats the purpose of the otherwise very capable engineering unit system.

Questions:

Is there any hidden way to add custom SI derived units for “Force per Length”?
Is this a known limitation in Prime 12?
Are there plans to add proper SI derived units like N/m and kN/m in future versions?

It feels very strange that imperial force-per-length units are included by default, while the most common SI engineering equivalent is missing.

I would really appreciate clarification or a better workflow from experienced users or PTC staff.

LucMeekes · Answer

You don’t need to divide the result by the desired unit (N/m), but you can multiply the displayed unit ( kg/s² ) with the desired unit (N/m), to make kg/s² disappear. But you'd have to do that for every result.

Custom units are possible since Prime 11, but it's not the holy grail, apparently.

I Assume, in your example, you have chosen SI as the base for your custom units. Then it's a shame (or rather crime!) that you only can choose non-SI units to choose from for force per length.
Consider submitting this as a severe bug.

Note that kpi, klf and plf are (defined as) ‘single’ units, which may be a limitation for the Custom units functionality. You can define N/m as a ‘single’ unit as well using: