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How to have BC Dynamics365 convert different units of measure?

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Posted on by CU06110724-0

Hi all,

We are in the process of switching to Dynamics 365, and in this context, I have a question about a problem that I simply cannot solve no matter what I try. For our inventory management, we have different units of measure – this is because the base unit is one thing (for inventory counting, issuing, etc.) and the purchase unit is something else (set up according to what we are invoiced for). For example, we have a canister (DK) as the base unit, but the purchase unit is KG. One canister equals 3.5 kg, so when I create a purchase order, it should convert to canisters. For example, I buy 87.5 KG at a time, which equals 25 canisters – but when it is received into inventory, it is posted as 24.99963 canisters, which in our view is incorrect – because we will never issue 0.99963 of a canister.

My question is whether something can be done with the conversion factor and rounding precision – I have tried, but I get errors. Under units, I have chosen to say that KG quantity per unit is 0.28571 canisters, since you cannot have more decimals, but I cannot set the quantity rounding precision to 1; I simply get an error. What can be done? It is critical for me to have the purchase unit in KG because we are invoiced in KG and the base unit in canisters because we issue and count in canisters.

Thanks in advance.

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Dynamics 365 Business Central

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Pallavi Phade 5,420 Super User 2026 Season 1 on at

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Namaste @CU06110724-0

In Item card there are three unit of measure , Base unit of measure , purchase unit of measure , Sales unit of measure

Base is used as Inventory calculation , Purchase unit of measure will appear while doing purchase and sales unit of measure while doing sales .

I have set an example 1 Carton = 100 pcs , PC is Base UOM

To put relation

1 CARTON = 100 PCS ;defined as below

Check Qty. Rounding Precision in Item

If you have done any transaction it will not allow to change any unit of measure . In that case you have to block that item

Regards

Pallavi Phade

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CU06110724-0 34 on at

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Hi Pallavi Phade

First of all, thank you for your message and for your help.

Unfortunately, our base unit is in canisters (DK), and therefore it is higher than the purchase unit, which is in KG. This is the reason why I am getting this error. If the base unit were the smallest "number," then it would have no problem converting, but as mentioned, it is the other way around in the case of this item.

I am currently working in a test environment, so fortunately it’s “free play” to try out different solutions.

Kind regards,

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Rishabh Kanaskar 6,219 Super User 2026 Season 1 on at

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Hi,

Business Central handles unit conversions through the Units of Measure setup and the Qty. per Unit of Measure field.

> Set the base unit (e.g., Canister) on the item card. Add KG as an additional unit of measure and define Qty. per Unit of Measure (e.g., 1 KG = 0.28571 Canisters).
> Business Central uses the Quantity Rounding Precision from the Unit of Measure setup. If you set it to 1, the system will round to whole numbers, but this only works if the conversion does not break consistency with the decimal precision allowed in transactions. If you get an error, it means the rounding conflicts with the calculated quantity.

Best Practice

> Keep the conversion factor accurate (e.g., 1 Canister = 3.5 KG).
> Use Qty. per Unit of Measure for KG as 3.5.
> Set Quantity Rounding Precision to 1 for the base unit (Canister) and a suitable precision for KG (e.g., 0.00001).

Accept that Business Central will calculate decimals internally, but you can configure Item Tracking or Lot Handling to ensure you only issue whole canisters operationally.

There is no way to force Business Central to always round to whole units during posting without custom development or an extension, because the system maintains financial accuracy.

Thanks

Rishabh

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CU06110724-0 34 on at

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Hi Rishabh Kanaskar

While I appreciate you taking the time to help sorting out this problem - it just doesn't seem to work.
I think it is as you mentioned above - that BC can not be forced to always round to whole units without custom development or an extension.

Thank you very much nevertheless.

Kind regards

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Jainam M. Kothari 15,732 Super User 2026 Season 1 on at

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Hello,

You're facing a unit conversion issue in Dynamics 365 where your base unit is canisters (DK) and your purchase unit is kilograms (KG), with 1 canister = 3.5 KG. When receiving inventory, the system posts fractional canisters (e.g., 24.99963 instead of 25), which is problematic since partial canisters aren't usable. This happens due to decimal precision limits and rounding settings.

To resolve it, you can define unit conversions with rounding precision at the product level, use a custom purchasing unit like “KG-Canister,” or manually override PO line conversions.

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Valentin Castravet 32,152 Super User 2026 Season 1 on at

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Best practice is to set the smallest unit as the Base Unit of Measure. In your case, use kg as the base, not canisters, this avoids the rounding issue you’re seeing.

If you can’t use kg as the base, adjust the Quantity Rounding Precision on the Item Units of Measure page. More info here - Rounding for base unit of measure - Dynamics 365 Release Plan | Microsoft Learn

Valentin Castravet
Work: Zander ERP Services
Blog: Dynamics 365 Business Central Insights
LinkedIn: www.linkedin.com/in/valentin-c-0500a247/

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Gregory Mavrogeorgis 992 Super User 2026 Season 1 on at

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Hi,

Yep—this is just rounding from the KG→canister conversion.
What’s happening
You set KG as a purchase UOM with Qty. per UOM ≈ 0.28571 (because 1 canister = 3.5 KG ⇒ 1 KG = 0.285714… canister). When you buy 87.5 KG, BC multiplies 87.5 × 0.28571 = 24.99963 canisters. If BC is allowed to keep many decimals on the base unit, you’ll see 24.99963 instead of 25.
The fix (keep base in whole canisters)
Do not round KG to 1. You want to round the base unit (canister) to whole numbers.

Item → Related > Units of Measure

DK (base):

Qty. per UOM = 1

Qty. Rounding Precision = 1

Rounding Type = Nearest (or Up if you never allow half cans)

KG (purchase):

Qty. per UOM = 0.28571 (≈ 1/3.5)

Qty. Rounding Precision = 0.001 (or 0.01) so you can buy/invoice by weight

Try your test again (87.5 KG). The posted base quantity should round to 25 canisters.

If you still get an error when setting DK’s Qty. Rounding Precision to 1, you’re probably editing the KG line or a generic UOM, not the Item’s DK line. Open the item’s Units of Measure lines (per-item), not the global UOM list, and change DK there. If it still blocks you, tell me the exact error text and I’ll pinpoint the setting that’s in the way.

If you have found this helpful please mark it as verified

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CU06110724-0 34 on at

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Hi Gregory Mavrogeorgis,

Thank you for the comment.

Can you confrim if I am on the right track? Rounding precision for DK is set to 1 but I'm not sure as of where I should set the rounding precision for KG.

Thank you in advance.

Kind regards,

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OussamaSabbouh 12,760 Super User 2026 Season 1 on at

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Hello,

Set the base unit to canister and purchase unit to KG. Then, on Item Units of Measure, adjust:

Qty. Rounding Precision (try 1 or a small value like 0.00001).

Qty. per Unit slightly (e.g., 3.49999).

This minimizes decimal rounding so received quantities stay whole.

Ref: Set Up Units of Measure – Microsoft Learn

Regards,

Oussama Sabbouh

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CU06110724-0 34 on at

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Hi OussamaSabbouh,

Thank you for your comment.

The system won't let me chance the QTY pr. base unit as it must be 1.

Kind regards,

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