Inventory

Secondary Unit

An alternate unit of measurement used alongside the primary unit for an item

Definition

A secondary unit is an alternate unit of measurement assigned to an inventory item in addition to its primary unit. It allows businesses to buy, sell, and track the same item in two different measurement units with a defined conversion factor between them. For Indian small businesses, secondary units are practical because goods are often purchased in one unit (like kilograms or boxes) and sold in another (like grams or pieces). For example, you may buy rice in 50 kg bags from a wholesaler but sell it in 1 kg packets to retail customers. The secondary unit feature lets you maintain stock in both units simultaneously, with automatic conversion. This eliminates manual calculation errors and provides flexibility in billing — you can create purchase invoices in bags and sales invoices in kilograms without confusion. Secondary units are also useful for businesses dealing in liquid goods (litres vs. millilitres), length-based goods (metres vs. feet), or packaged goods (boxes vs. individual pieces).

How It Works

  1. 1You define a primary unit (e.g., Kilogram) and a secondary unit (e.g., Gram or Packet) for an inventory item, along with the conversion factor between them.
  2. 2When purchasing, you can enter quantities in whichever unit the supplier bills — for example, 50 kg bags — and the system stores it in both units.
  3. 3During sales, you bill in the unit your customer prefers — for example, 250g packets — and the stock is automatically deducted in both units using the conversion factor.
  4. 4All stock reports, valuation, and reorder alerts work correctly in both units, so you always know your inventory regardless of which unit you think in.

Example

You sell cooking oil in Coimbatore. Primary unit: Litre, Secondary unit: 500ml Bottle. Conversion: 1 Litre = 2 Bottles. You purchase 200 Litres (= 400 Bottles) at Rs. 150/Litre = Rs. 30,000. A retail customer buys 6 Bottles — the system calculates this as 3 Litres and bills Rs. 450 (6 x Rs. 75 per bottle). Your stock reduces to 197 Litres or 394 Bottles. Both units stay in sync automatically.

How Stock Register Handles This

  • Define custom conversion factors for any unit pair — kg to grams, boxes to pieces, litres to bottles, metres to feet
  • Bill customers in either unit and the app auto-converts stock deductions to keep both units in sync
  • Purchase in bulk units and sell in retail units without any manual conversion calculations
  • View stock reports in your preferred unit with the option to toggle between primary and secondary units

Related Terms

Related Guides

Frequently Asked Questions

Can I set different selling prices for primary and secondary units?

Yes, you can set prices for both units independently. For example, cooking oil might be priced at ₹150 per litre (primary) and ₹80 per 500ml bottle (secondary). The app handles the billing correctly based on which unit you select during invoicing.

What if my conversion factor is not a round number?

Stock Register supports decimal conversion factors. For example, if 1 box = 144 pieces (gross), or 1 kg = 2.2 pounds, you can enter the exact ratio and the system will calculate conversions accurately.

Can I add more than one secondary unit for an item?

Typically, you can define one secondary unit per item with a conversion factor to the primary unit. If you need to track a third unit, you can use the primary-secondary pair that covers your most common buying and selling scenarios.

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