Guide
How to Calculate Cost Per Unit When You Buy in Bulk
Work out the true cost of each item you make by dividing batch materials cost by items per batch, so you price correctly when you buy ingredients in larger quantities.
Why batch cost matters for makers
When you start, you buy small quantities of materials—a jar of fragrance oil here, a kg of wax there. As your business grows, you buy bigger batches to lower the per-unit cost. A liter of fragrance oil is cheaper per ml than a 100ml bottle. A 10kg bag of soap base is cheaper per kg than a 1kg tub. But if you do not recalculate your cost per unit, you will not realize you can afford to hold margin instead of charging less.
Many makers make this mistake: they know their current materials spend per item (say $2 for a candle at small-quantity prices), but they forget to recalculate when they switch to bulk ordering and the actual cost drops to $1.20 per candle. They keep charging the same price and think they're making the same margin, when in reality they're keeping $0.80 more per item.
The sum: divide batch cost by items in the batch
Cost per unit = (total cost of the batch of materials) / (number of items you make from that batch)
Example: if you buy a 5kg bag of wax for $30 and you make 100 candles from it, the wax cost per candle is $30 / 100 = $0.30 per candle (not the $0.60 you were paying before when you bought smaller bags).
Include everything: not just the main material, but fragrance, dye, packaging, labels, and any other item that goes into the finished product.
A worked example
A soap maker buys ingredients for a batch of 200 bars: - Bulk soap base (5kg): $40 - Fragrance oil (250ml): $12 - Colorant and mica: $5 - Labels: $8 - Packaging boxes: $10 - Total batch cost: $75
Cost per bar: $75 / 200 = $0.375, which she rounds to $0.38 per bar.
Previously, when she bought smaller quantities, her cost per bar worked out at $0.45. By buying in bulk, she saved $0.075 per bar.
If she was charging $4 per bar based on the old $0.45 cost, she now keeps an extra $0.075 per bar profit. On 200 bars, that is $15 per batch, or $180 a year if she makes one batch a month.
Update your price or your margin
Once you know your new unit cost from bulk buying, you have two choices:
- Keep your price the same and take higher margin. If your candles sold at $6 before and your cost came to $2, you kept $4 margin. If your new cost is $1.20 (because of bulk wax), you keep $4.80 margin. That money goes toward your labor and business overheads.
- Lower your price slightly to stay competitive. If competitors' prices have fallen, you could drop your $6 candle to $5.50 and still keep a strong $4.30 margin. This helps you win more customers without cutting into your survival costs.
Which you choose depends on your market and whether you are focused on volume or margin.
Recalculate when suppliers or quantities change
Every time you change suppliers, or you find a bulk discount at your current supplier, recalculate cost per unit. Track it so you notice when economics shift. Some materials are seasonal (certain oils or butters spike in price at certain times of year), so recalculate quarterly.
Put it in a sheet. Our Maker's Costing Workbook helps: enter each material's pack size and price, a recipe for each product and the units per batch, and the workbook works out batch cost and cost per unit. Change the quantities and see the cost per unit adjust.
