Average Unit Cost in Stocky: How It Works and How to Preserve Your Data

One of the most valuable features in Stocky is something many merchants take for granted until they are about to lose it: weighted average unit cost tracking. If you rely on Stocky for margin analysis, COGS reporting, or simply knowing what your products actually cost you, you need to understand how this data works, where it lives, and how to preserve it before the Stocky shutdown on August 31, 2026.

What Is Average Unit Cost?

Average unit cost, sometimes called weighted average cost or moving average cost, is an inventory costing method that calculates the cost of a product by averaging the cost of all units currently in stock, weighted by the quantity received at each price.

Here is a concrete example.

Suppose you sell a candle that you purchase from a supplier. Over three purchase orders, you bought:

PO	Quantity	Unit Cost	Total Cost
PO-001	100 units	$5.00	$500.00
PO-002	50 units	$5.50	$275.00
PO-003	150 units	$4.80	$720.00

After receiving all three POs (and assuming no sales between them), your total inventory is 300 units and your total cost is $1,495.00. Your weighted average unit cost is:

$1,495.00 / 300 = $4.98 per unit

This is different from simply taking the average of the three unit costs ($5.00 + $5.50 + $4.80) / 3 = $5.10, because the weighted average accounts for the fact that you bought more units at the lower price.

How Stocky Calculates It

Stocky recalculates the weighted average cost every time you receive inventory against a purchase order. The formula is:

New Average Cost = (Existing Inventory x Old Average Cost + Received Quantity x Received Unit Cost) / (Existing Inventory + Received Quantity)

This means the average cost is a “living” number that updates with every PO receipt. If your supplier raises prices, your average cost gradually increases. If you negotiate a better price, it gradually decreases. The weighting ensures that larger orders have a proportionally larger impact on the average.

Stocky also handles partial PO receipts. If you receive 80 of 100 ordered units, it recalculates based on the 80 received, not the 100 ordered. The remaining 20 units will be factored in when (and if) they arrive.

What Happens When You Sell Units

When you sell a unit, Stocky uses the current average cost as the cost basis for that sale. This is what feeds into COGS (cost of goods sold) calculations. The average cost itself does not change when you sell; it only changes when you receive new inventory.

This is important for understanding your margins. If your average cost is $4.98 and you sell at $12.00, your gross margin per unit is $7.02, or about 58.5%. This is more accurate than using the latest purchase price, which might overstate or understate your actual cost basis.

Why Average Unit Cost Matters

Accurate COGS Reporting

Cost of goods sold is one of the most important numbers in retail accounting. It directly affects your gross profit, your tax liability, and your understanding of business health. Using a weighted average cost gives you a COGS figure that reflects your actual purchasing history, not just your most recent order.

Margin Analysis

If you set retail prices based on target margins, you need accurate cost data. A product with a $5.00 cost and a $15.00 retail price has a 67% gross margin. But if your actual weighted average cost is $5.80 because recent orders were more expensive, your real margin is 61%. That difference matters at scale.

Tax Reporting

Depending on your jurisdiction, inventory valuation directly affects your taxable income. The IRS and CRA both accept weighted average cost as a valid inventory costing method. Your year-end inventory valuation (units on hand multiplied by average cost) feeds into your tax return, either directly or through your accountant.

Informed Purchasing Decisions

Knowing your true average cost helps you negotiate with suppliers. If a supplier quotes you $5.50 per unit but your current average cost is $4.80, you can see exactly how that order will shift your cost basis. It also helps you evaluate whether switching suppliers or consolidating orders would meaningfully lower your costs.

Shopify’s Native Cost Field vs Stocky’s Average Cost

Shopify has a built-in “cost per item” field on every product variant. This is a single static value. It does not automatically recalculate when you receive new inventory. It is simply whatever number was last entered, whether manually by you, by an app, or via a CSV import.

Here is how the two systems compare:

Feature	Stocky Average Cost	Shopify Cost Per Item
Recalculates on PO receipt	Yes, automatically	No
Weighted by quantity	Yes	Not applicable (static)
Historical tracking	Yes, maintains running average	No, current value only
Feeds into COGS reporting	Yes, within Stocky reports	Only if manually kept current
Editable manually	Yes, can be overridden	Yes
Survives Stocky shutdown	No	Yes

The critical issue: Stocky’s calculated average cost and Shopify’s cost-per-item field may show different values. If you have been relying on Stocky for cost data and never manually updated Shopify’s native field, the native field may be outdated or inaccurate.

After the Stocky shutdown, only Shopify’s native field will remain. If that field does not reflect your true costs, your margin data in Shopify reports will be wrong.

How to Export and Preserve Your Cost Data

Follow these steps before the August 31, 2026 shutdown.

Step 1: Export from Stocky

Open Stocky in your Shopify admin.
Navigate to Products (or Inventory, depending on your Stocky version).
Look for an Export option. Export all products as CSV.
Make sure the export includes the average cost or weighted average cost column.
Save this file with a clear name like stocky-average-costs-2026-02.csv.

Step 2: Export from Shopify

In Shopify Admin, go to Products > All Products.
Click Export and export all products as CSV.
This file will include the Variant Cost column, which is Shopify’s native cost-per-item field.

Step 3: Compare the Two Exports

Open both files and compare the cost values for each variant. You will likely find discrepancies. Common reasons:

Stocky’s average cost updated with every PO receipt; Shopify’s field was not updated.
You (or staff) manually changed Shopify’s cost field at some point.
Stocky was set to write back to Shopify’s cost field, but the sync was inconsistent.

For each variant, determine which cost value is more accurate. In most cases, Stocky’s weighted average is the better number if you have been actively receiving POs through Stocky.

Step 4: Update Shopify’s Native Field

Once you have determined the correct cost for each variant, update Shopify’s native “cost per item” field to match. You can do this via CSV import:

Create a CSV with columns: Handle, Variant SKU, Variant Cost.
Populate the Variant Cost column with the correct values (typically from Stocky).
In Shopify Admin, go to Products > All Products > Import.
Upload the CSV. Shopify will update the cost field for matching variants.

This ensures that after Stocky is gone, Shopify’s built-in reports use accurate cost data.

Step 5: Archive Your Stocky Cost History

Even after updating Shopify’s native field, keep your Stocky exports. The weighted average cost history has value:

You may need it for tax audits covering periods when Stocky was active.
It provides a historical record of cost trends for supplier negotiations.
If you later migrate to an app that supports weighted average tracking, you may be able to import this history.

What Happens After Stocky Is Removed

After August 31, 2026:

Stocky’s average cost data disappears. It is stored within the Stocky app, not in Shopify’s core database.
Shopify’s native cost field persists. Whatever value is in the “cost per item” field stays.
No automatic recalculation occurs. Shopify’s native field does not update when you receive inventory from suppliers. You will need to update it manually or use a replacement app.
COGS accuracy degrades over time. If your purchase costs change and you do not update the native cost field, your margin and COGS data in Shopify reports will become increasingly inaccurate.

This is the fundamental challenge: Stocky provided a living, automatically updated cost basis. Without it, you either accept a static cost value (and the inaccuracies that come with it) or you adopt a replacement tool that offers the same automatic recalculation. For a broader look at pricing and feature tradeoffs in replacement tools, see our analysis of ERP vs. Stocky pricing considerations.

Moving Forward

If accurate cost tracking matters to your business, and for any merchant doing serious margin analysis or tax reporting, it should, then finding a Stocky replacement that supports weighted average cost is a priority.

When evaluating alternatives, ask specifically:

Does the app calculate weighted average cost automatically on PO receipt?
Does it write the calculated cost back to Shopify’s native cost field?
Can it import historical cost data from a CSV?
Does it provide COGS and inventory valuation reports?

These four capabilities will determine whether your cost data remains accurate after the transition.

Start by exporting your data today using the steps above. For the full migration timeline and checklist, see our guide: Stocky Is Shutting Down Aug 31, 2026: What You Need to Do Now.