Weighted Average Costing for Small Makers — Why It's the Right Method
Weighted average costing is IRS-approved, GAAP-compliant, and the right choice for small-batch makers with fluctuating material costs. Here's why — and how Craftybase automates it.
You’ve decided you need to track COGS properly. Good. Now comes the question most makers don’t know to ask: which costing method should I use?
There are three options recognised under US GAAP and IRS rules — FIFO, LIFO, and weighted average. Each assigns costs differently, which means each produces different COGS figures, different inventory values, and a different tax bill. Picking the wrong one doesn’t just create headaches at tax time. It can mean you’re systematically mispricing your products all year.
For most small-batch makers, weighted average costing is the right answer. Not because it’s the easiest to explain — though it is relatively simple — but because it most accurately reflects how a handmade production business actually works. This post makes the case for why.
If you want to understand the mechanics of how weighted average cost is calculated, that’s covered in detail here. This post is about the business decision: why weighted average, why not FIFO, and what it means for your numbers.
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The problem with costing methods most makers don’t realise they have
A lot of makers start tracking COGS without really choosing a method. They might record the last price they paid for a material, or average a couple of purchases together in a spreadsheet, or just use whatever number feels right. That works — barely — until prices change.
And prices change constantly. Lye goes up. Fragrance oil suppliers run out and you buy from a second source at a different price. Your beeswax supplier revises pricing mid-year. You stock up during a sale and then buy again at full price six months later.
When that happens, you’ve got the same material sitting in your workspace at multiple different costs. Which cost do you assign to the products you’re making today?
That’s not a rhetorical question. The IRS and GAAP both require you to have a consistent, documented answer. And that answer is your inventory costing method.
What the three methods actually do
Before arguing for weighted average, it’s worth being clear on what you’re choosing between.
FIFO (First In, First Out) assumes the oldest stock gets used first. So if you bought 500g of fragrance oil at $8/oz in January and another 500g at $10/oz in March, FIFO says your February production runs used the $8 oil — even if in reality you opened both bottles at once.
LIFO (Last In, First Out) assumes the most recent purchase gets used first. It produces higher COGS (and lower taxable income) when prices are rising, which is why some US businesses use it as a tax strategy. It’s prohibited under IFRS and unavailable outside the US.
Weighted average cost doesn’t try to simulate which physical units got used when. Instead, it blends all purchases together into a rolling average. When you buy at a new price, the average adjusts based on what you already have on hand. Every production run that follows uses that blended cost.
For the technical walkthrough of the formula and the step-by-step table, see the weighted average cost method explained.
Why FIFO is harder than it sounds for makers
FIFO looks straightforward on paper. In practice, it requires you to track purchase layers — to know exactly which batch of material you’re drawing from for each production run. This is called FIFO lot tracking.
For a food manufacturer with strict expiry dates, that tracking is unavoidable. You genuinely need to know which specific inventory is moving. But a soap maker using coconut oil? A candle maker using soy wax? You’re not rotating stock by lot. You pour from whatever container is open. Physically separating “January’s batch” from “March’s batch” on a shelf isn’t how your workshop runs.
FIFO for makers means one of two things: either you impose artificial lot-tracking procedures that don’t match how you actually work, or you maintain a fiction in your records that could create inconsistencies if audited.
Weighted average sidesteps this entirely. There are no lots to track. The rolling average just reflects the blended cost of everything you have — which is much closer to what your inventory actually represents.
The real reason weighted average fits makers: fluctuating material costs
Small-batch makers almost always buy the same materials repeatedly at different prices. That’s just the nature of sourcing raw materials as a small business — you don’t have the volume to lock in annual contracts.
This is where weighted average costing specifically earns its place. Consider a soap maker buying shea butter across a year:
| Purchase | Quantity | Unit Cost | Running Avg After Purchase |
|---|---|---|---|
| January | 2 kg | $12.00/kg | $12.00/kg |
| April | 3 kg | $15.00/kg | $13.80/kg |
| August | 2 kg | $14.00/kg | $13.86/kg |
| November | 4 kg | $16.50/kg | $15.02/kg |
Notice what happens. The average moves each time, but it doesn’t jump sharply — it blends in the new price relative to how much stock is already on hand. A November purchase at $16.50 raises the average, but it doesn’t suddenly make all your products cost as if you’d paid $16.50 all year.
Under FIFO, that November production run would be costed using the oldest stock still on hand (the April purchase at $15.00, assuming January and August stock had been depleted). You’d need to know that. Under weighted average, you just use the current running average of $15.02 — which automatically reflects your actual blended cost.
For makers with 10, 20, or 50+ different materials, each with their own purchasing history, maintaining FIFO lot records for all of them is a significant administrative burden. Weighted average achieves more accurate results for your actual situation with less tracking overhead.
IRS and GAAP compliance — what you actually need to know
The IRS requires businesses with inventory to use a consistent valuation method and declare it. You don’t need to file special paperwork, but you do need to pick a method and apply it consistently year to year. Changing methods mid-year requires IRS approval (Form 3115).
Both FIFO and weighted average are acceptable under both US GAAP and IRS rules. LIFO is GAAP-compliant (US only) but barred under IFRS, so if you have international customers or investors it creates complications.
The compliance case for weighted average specifically: Because it produces a blended, smooth average rather than requiring layer-by-layer tracking, it’s significantly easier to audit. Your cost per unit at any point in time is a single calculable number based on documented purchases. There’s no ambiguity about which lots were consumed.
If you’re ever audited, “I use weighted average cost — here are my purchase records” is a defensible, clean position. “I use FIFO but I didn’t actually track which batches I used” creates problems.
How this affects your COGS and your tax bill
The costing method you choose directly affects how much COGS you report, which affects your net profit, which affects your tax liability.
When material costs are rising (which they often are for makers), the three methods produce this ordering:
- FIFO: Lower COGS (using older, cheaper costs) → higher reported profit → higher tax bill
- Weighted average: Middle — blends old and new costs → moderate profit and tax
- LIFO: Higher COGS (using newer, pricier costs) → lower reported profit → lower tax bill (US only)
LIFO’s tax advantage is real — which is why some larger US manufacturers use it. But it comes with significant recordkeeping complexity and is unavailable outside the US.
For most small makers, the difference between FIFO and weighted average isn’t large enough to meaningfully affect tax strategy. What matters more is consistency and accuracy. Weighted average gives you COGS figures that genuinely reflect your blended material costs — making them more useful for pricing decisions throughout the year, not just at tax time.
Weighted average costing and your pricing decisions
Here’s a practical angle that often gets missed: your costing method affects how you set prices, not just what you report at year-end.
If you use FIFO and prices are rising, your recorded COGS will initially look low (using older, cheaper stock). That might make a product seem more profitable than it is. When you eventually work through the cheaper stock and start costing against your more recent, pricier purchases, your margin shrinks — but your price is already set.
Weighted average adjusts continuously. If your shea butter average creeps up from $12 to $15 over the year, your cost per bar of soap creeps up proportionally. You can see the margin erosion happening in real time and respond — adjusting prices, sourcing alternatives, or making batch-size decisions — rather than discovering it at year-end.
That ongoing visibility into true cost is one of the reasons Craftybase is built around weighted average costing. It’s not just about compliance. It’s about having numbers you can actually use to run your business.
How Craftybase handles weighted average costing automatically
Craftybase implements weighted average costing as a perpetual system — meaning the rolling average updates every time you record a purchase, not just at year-end.
Every time you log a material purchase, Craftybase recalculates the average unit cost using the formula:
New weighted average cost
(Current stock value + New purchase value) ÷ (Current units on hand + New units purchased)
You don’t enter this formula anywhere. You just record your purchases. Craftybase runs the calculation in the background and keeps your cost-per-unit current.
When you record a manufacturing run — say, you make 24 bars of soap — Craftybase draws on the current weighted average costs for each material in your recipe to calculate the total production cost. That cost flows through to your finished goods inventory and, when you sell, to your COGS report.
This chain — purchase → rolling average → recipe costing → COGS — is automated. What would take hours of spreadsheet work across dozens of materials and hundreds of purchases runs in the background every time you update your records.
The result: your COGS figures for Schedule C at year-end aren’t a scramble. They’re just a report you pull, based on actual weighted average costs tracked throughout the year.
Weighted average vs. FIFO — a direct comparison for makers
| FIFO | Weighted Average | |
|---|---|---|
| Tracks purchase lots? | Yes — required | No — not needed |
| Good when prices fluctuate? | Creates complexity | Handles naturally |
| Admin overhead | Higher | Lower |
| COGS accuracy for makers | Depends on lot discipline | High, automatically |
| IRS/GAAP compliant? | Yes | Yes |
| Works in perpetual inventory? | Yes | Yes (ideal) |
| Used by Craftybase? | No | Yes |
For makers who buy the same materials repeatedly at varying prices — which is almost every soap, candle, jewelry, and cosmetics maker — weighted average is the lower-friction, higher-accuracy choice.
Frequently Asked Questions
Is weighted average costing IRS-approved for small businesses?
Yes. Weighted average cost is an IRS-approved inventory valuation method under both US GAAP and IRS rules. It's accepted for all business sizes, including sole proprietors filing Schedule C. The key requirement is consistency — you pick a method and stick with it. Changing methods mid-year or across tax years requires IRS approval via Form 3115.
Should I use FIFO or weighted average cost for my handmade business?
For most handmade businesses, weighted average is the better choice. FIFO requires you to track exactly which purchase lots were consumed in each production run — practical for food producers managing expiry dates, but unnecessary overhead for makers using commodity materials like wax, resin, or fragrance oil. Weighted average gives you accurate COGS without lot-level tracking, which is more realistic for how small-batch production actually works.
How does weighted average costing affect my COGS when material prices change?
When you buy materials at a new price, the weighted average adjusts gradually — blending the new cost with what's already on hand. A single higher-priced purchase doesn't spike your COGS immediately; it nudges the average proportionally based on quantity. This makes your cost data more stable than FIFO (which can jump sharply when older stock runs out) and gives you a clearer picture of your true blended material costs throughout the year.
Does Craftybase automatically calculate weighted average costs?
Yes. Craftybase uses perpetual weighted average costing by default — no setup required. Every time you log a material purchase, the running average unit cost updates automatically. Those updated costs flow through to your recipes, manufacturing runs, and COGS reports in real time. You record your purchases; Craftybase handles the costing math throughout the year, so your tax-time numbers are always current.
What's the difference between weighted average cost and a simple average?
A simple average just adds prices and divides by the number of purchases, ignoring how much you bought at each price. Weighted average accounts for quantity — if you bought 10 units at $5 and 1 unit at $20, a simple average gives $12.50, but the weighted average gives $6.36, which is far closer to what your inventory actually cost. For inventory, weighted average is the correct approach and the one accepted under IRS and GAAP rules.
Can I switch from FIFO to weighted average cost?
Yes, but it requires IRS approval. Changing your inventory costing method is considered a change in accounting method and must be reported using Form 3115 (Application for Change in Accounting Method) in the year you make the change. The IRS generally permits this change — it's not unusual for growing businesses to move to a more automated method. Talk to your accountant before switching, particularly if you carry significant inventory value.
The method you use to cost your inventory isn’t a minor accounting technicality. It shapes what you know about your margins, how you price, and what you report at tax time. For small-batch makers buying the same materials repeatedly at changing prices — which is almost everyone — weighted average costing gives you accurate, auditable COGS without the overhead of lot-level tracking.
Craftybase handles this automatically, so the question of “which costs do I assign to which batch?” just stops being a question you have to answer. Your numbers stay current without the spreadsheet work.
