Rounding error when converting from alternative UoM to base UoM

[marko_kunsic]

Hi guys,

Let's say we have material 500392 with base UoM KG and alternative UoM M2.

When I convert quantity 293,000 KG (which is also in quant table and quantity in transfer order...) to alternative UoM,

I get 75,075 M2, but this is already rounded value (the exact value is 75,074733096... - see picture below).

The problem is that on label is bar code with quantity 75,075M and if I convert this value back to base UoM, I get

293,001 KG ! (because 75,075 was already rounded value)

If I look material quantity in LS26 and convert back and forth between different UoM, I've got proper result ( 293,000 KG vs 75,075 M2 ).

But this is probably because SAP do not internaly convert (recalculate) explicitly from alternative UoM back to base UoM (it already has exact value in base UoM).

Any suggestions how to solve the problem?

Probably with this concept there is no way to properly do conversion (garbage in, garbage out).

Thank you very much,

Marko

[Former Member]

Marko,

I stumbled upon your post as I was searching for something.  I realize this is a very old post and that you have probably given up on ever finding and a solution, but on the slight chance that you would still welcome a solution, I'll reply.  First, here's http://scn.sap.com/docs/DOC-51334 a paper that gives a detailed description of how to resolve this issue.  The key is to eliminate the residual error (the difference between the theoretical calculation and the rounded value) so that the conversion is exact in both directions (Alt to Base, and Base to Alt).  In this situation it looks like your global conversion factors are 72 M2 <> 281 KG.  There are two basic scenarios generally encountered: Fixed Increment Materials and Variable size Materials.  Each scenario and solution are explained below.

Fixed Increment – This basically means that you have a fixed size product.  So if all of the rolls (I assume we are talking about rolls, but it doesn’t really matter) are the same size, that’s the scenario we are dealing with.  In this situation you will need to adjust the conversion factors ever so slightly so that 75.075000… M2 = 293.000000… KG.  Using the technique described in the aforementioned paper we calculate new conversion factors to be 3003 M2 <>11720 KG.  If you use these new conversion factors everything will work as you hoped.  (If you are concerned about adjusting the global factor let’s compare the two ratios.  The theoretical ratio is 281/72 = 3.90277777777778.  The proposed new value is 293/75 = 3.9027639027639 which is a difference of -0.00036%.  So it's a miniscule difference AND it gives the correct result).

Variable Size – This basically means that the rolls are different sizes.  To resolve this scenario you will need to use batch specific UOMs.  Rather than trying to explain how that works here (it is fairly complex) I suggest you check out the paper.

I hope this helps.  If you are still looking for an answer and want to chat more, just let me know.

Good luck,

Dave