---
title: "UOMs"
space: "ERPNext"
url: "https://www.prilk.com/docs/erpnext/uoms"
updated: "2026-05-15"
---

## UOMs (Units of Measure)

A UOM is how an item is measured — Nos (number of), Litre, Kg, Hour, Box, Pallet. Every Item has a Default UOM, and quantities on documents inherit from it.

### Where to manage

**UOM** in the Awesome Bar → list view. ERPNext seeds standard UOMs (Nos, Box, Pcs, Kg, Litre, Meter, Hour, Day, Minute, …).

### Adding a new UOM

For specialised units (Roll, Sheet, M³, Carton):

1. **UOM → New**
2. **UOM Name** — what it's called
3. **Must be Whole Number** — Yes for countable units (Nos, Box), No for measurable (Kg, Litre)
4. Save

Items can now use this UOM as Default.

### Setting an item's Default UOM

On the Item record:
- **Default Unit of Measure** — primary unit; quantities on all documents default to this

For most items, "Nos" (number of pieces) is fine. For materials sold by weight (Kg, Litre), pick accordingly.

### Selling and buying in different UOMs

Often you buy in one unit and sell in another — buy by Box, sell by Piece. ERPNext handles this via **UOM Conversion**:

1. Open the Item → **UOMs** child table
2. Add the alternate UOM (e.g., Box)
3. Set **Conversion Factor** (e.g., 1 Box = 24 Pcs)

Now when you create a Purchase Order in Box, ERPNext multiplies by the conversion factor for stock posting in the Default UOM (Pcs).

### Pricing across UOMs

Item Prices can be in any UOM. The conversion factor handles math:
- Buying Price: €100 per Box (= 24 Pcs)
- Selling Price: €5 per Pc
- ERPNext computes margins and totals correctly

### Stock UOM vs Transaction UOM

Stock is always tracked in the Item's Default UOM (the Stock UOM). Even if you buy in Boxes and sell in Pcs, your warehouse balance shows Pcs.

This means:
- Stock Balance reports show Default UOM only
- Re-order levels and quantities are in Default UOM
- UOM Conversion Factors must be accurate — wrong factor = wrong stock balance

### Common situations

- **Bulk materials** — Kg or Litre default, with Drum / Tank as alternate UOMs for buying
- **Items with case packs** — Pcs default, Box as buying UOM
- **Services billed by Hour** — Hour as default, no alternate UOMs needed
- **Items sold by length** — Meter or Foot default; Roll as alternate (1 Roll = 50 Meters)

### Changing an item's Default UOM

You can change Default UOM **only before** the item has had stock movements. After that, the historical stock entries are tied to the original UOM — changing it would break the math.

If you really need to change: create a new Item with the new UOM, transfer balance over via Stock Reconciliation, retire the old item.