📊 What is WAC (Weighted Average Cost)?
WAC stands for Weighted Average Cost
It’s an accounting method used to track your parts costs more accurately over time.
Instead of using the last purchase price or a fixed cost, WAC averages the cost of all units you buy. Every time you receive more stock at a different price, EasyTruckShop recalculates the average cost per unit automatically.
✔️ Why Use WAC?
Keeps your parts profit margins accurate, especially when vendor prices change often.
Prevents manual cost mistakes when you buy the same part at different prices.
Ensures you’re not under- or over-charging on parts sales or repairs.
Example:
You bought 10 filters at $5.00 each.
Later you buy 10 more at $7.00 each.
Your WAC for those filters is now $6.00 per filter (total cost divided by total units).
⚙️ How WAC Works in EasyTruckShop
1️⃣ When you receive a PO
If you’re using WAC, every time you receive more units of a part with a different purchase cost, ETS will automatically update the average cost for that part.
2️⃣ The new WAC applies
That updated average cost is what shows in your inventory reports and is used to calculate sales price if you’re using price matrices or markup rules.
3️⃣ No manual math
EasyTruckShop handles the calculation and applies it consistently.
💡 How Does WAC Affect My Sale Price?
WAC and your sale price are directly connected. Here's the full chain in plain language:
Your cost comes in when you receive a Purchase Order (PO). ETS records what you paid per unit.
WAC is calculated automatically. Every time you receive more stock at a different price, ETS averages your total cost across all units.
The Price Matrix applies your markup. It takes your current WAC and multiplies it by your markup percentage to set the sale price.
If your WAC goes up (e.g. vendor raised prices), your sale price goes up automatically — and vice versa.
📌 Key point: If your sale prices are changing unexpectedly, the most common reason is a WAC change from a recently received PO. Check your PO history for that part.
⚠️ What Can Change My WAC Unexpectedly?
Two things will change your WAC in ways you might not expect:
Receiving a PO with the wrong unit cost entered. Always double-check the cost field when receiving stock — this is the #1 cause of WAC errors.
Using Correct Stock with an incorrect cost. The Correct Stock tool lets you manually adjust quantity and cost. If you enter the wrong cost, it permanently affects your WAC.
✅ Rule of thumb: Always enter the actual cost you paid, not the selling price. Entering your sell price as your cost will throw off every margin calculation for that part.
✅ Good to Know
WAC only works when you receive stock properly through POs or when initially creating a part (this keeps your costs accurate.)
If you manually adjust quantities without updating costs, your WAC may be off (always receive through the correct workflow!)
WAC is great for shops with regular price changes from vendors.
Still have questions about WAC?
Check out the WAC FAQ & Troubleshooting article for step-by-step guidance on the most common WAC issues, including how to check a part's current WAC and what to do when costs look wrong.