I'm Using 10 Kg of Soy Wax Every Month — How Much Should I Order at Once so I Save on Cost Without Holding Unnecessary Inventory?

The two costs that set your order size

Most advice on buying in bulk assumes the per-kilo price falls as you buy more. On CSI's listed soy waxes that is mostly not true. I Currently Buy Soy Wax in 1 Kg Packs but Use 20 Kg Every Month — At What Point Does Moving to 10 Kg or 25 Kg Packs Make More Sense? shows the full ladder: CSI 464 is flat from 1 kg, Luxury Soy Wax Chunks are flat (the 10 kg bag is ₹0.90 dearer than two 5 kg bags), and Natural Soy Pearl breaks once, at 5 kg. When the price is flat, the order-size question becomes a classic stock question with two opposing costs.

Ordering cost is everything each order costs you regardless of its size: any delivery charge you pay, the time it takes you to place the order, receive it, check it and put it away, and the production time lost if a delivery is late. It is paid once per order, so fewer, bigger orders reduce it. Holding cost is what it costs to keep wax on the shelf: the cash tied up (which could be paying a loan or funding marketing), the space, and a small risk of damage. It grows with the average stock, so bigger orders raise it.

With those inputs the holding cost of one kilo of CSI 464 is ₹507.40 × 18% = ₹91.33 a year, or ₹7.61 a month. If you order Q kilos at a time and use them steadily, you hold Q ÷ 2 kilos on average. You place 120 ÷ Q orders a year. The order size that minimises the sum of the two costs is the square root of (2 × annual usage × ordering cost ÷ holding cost per kilo per year). For the example that is √(2 × 120 × 300 ÷ 91.33) = 28.1 kg. The formula is the textbook economic order quantity; it assumes steady use and a flat price, which is exactly your situation on CSI 464.

Order sizes from 5 kg to 60 kg, priced

The table runs seven order sizes through the example inputs. Every row buys the same 120 kg a year for ₹60,888.00. Only the ordering and holding columns change.

At these inputs, ordering 10 kg every month costs ₹4,056.66 a year in ordering and holding. Ordering 20 kg every two months costs ₹2,713.32, and 30 kg every three months ₹2,569.98. Going smaller is expensive because orders multiply: 5 kg every fortnight costs ₹7,428.33. Going much bigger is expensive because idle wax multiplies: 60 kg every six months costs ₹3,339.96 and keeps ₹15,222.00 on the shelf on average. The sweet spot here is 20 to 30 kg per order, two to three months of wax.

Plug in your own per-order cost

Because ordering cost is the most personal of the inputs, here is the best order size at five levels, keeping the example 18% a year holding rate and CSI 464's ₹507.40 a kg.

Two points follow. First, at 10 kg a month the answer stays between one and four months of wax across a wide range of ordering costs. That is a modest amount of stock, not a warehouse. Second, the holding rate matters as much as the ordering cost. If your cash is expensive, for example borrowed at a high rate, your best order size shrinks; if the cash would otherwise sit idle, it grows. Change the rate in the formula and re-run it. Should I Keep More Money in Cash or Use It to Buy Larger Quantities of Candle Raw Materials at Better Prices? covers the cash-or-stock question in more depth.

The reorder trigger

Order size answers how much. The reorder trigger answers when. At 10 kg a month you use about 0.33 kg a day. With an example delivery time of 7 days you need 2.33 kg to last until the new wax arrives. Add a buffer, here one week of usage (2.33 kg), for a slow delivery or a busy week. Your trigger is about 4.7 kg: when stock falls to that, order.

The buffer adds a fixed amount to your average stock whatever the order size, so it adds the same holding cost to every row and does not change which order size is cheapest. What it changes is how often you run out. If your sales are lumpy, raise the buffer rather than the order size. I'm Growing Quickly but Don't Want to Run Out of Wax — How Do I Set a Reorder Point Based on Monthly Consumption and Supplier Lead Time? sets the reorder point from usage and delivery time step by step, and I Use 50 Kg of Soy Wax Every Month and My Supplier Takes 10 Days to Deliver — At What Inventory Level Should I Reorder? works the same maths at 50 kg a month.

If your wax is not CSI 464

The same method works for any wax. Only the price per kilo changes, and with it the holding cost. At the example inputs, the best order size is about 26 kg for Luxury Soy Wax Chunks (₹599.00 a kg), 25 kg for Premium Coconut Soy Wax CSI 468 at its 5 kg rate of ₹637.00 a kg, and 31 kg for Natural Soy Pearl (₹424.80 a kg from 5 kg). Dearer wax is costlier to hold, so its best order is a little smaller.

Two waxes add a constraint. Natural Soy Pearl costs ₹450.00 a kg in a 1 kg bag and ₹424.80 from 5 kg, so an order under 5 kg throws away 5.6%. Its 50 kg pack is ₹21,240.00, the same ₹424.80 a kg, so at 10 kg a month it would be five months of wax for no extra saving. Premium Coconut Soy Wax CSI 468 steps from ₹650.00 a kg at 1 kg to ₹637.00 at 5 kg and 10 kg, a 2.0% break, so again order in 5 kg or 10 kg bags. For the Chunks, buy 5 kg bags where you can, since the 10 kg bag is ₹0.90 dearer than two 5 kg bags.

Where the formula stops

The order-size formula is a guide, not a law. It assumes steady use, a flat price, and that you have the space and cash for the answer. Real life adds limits. If your storage room gets hot in summer, keeping three months of wax there is a different risk from keeping it in a cool store; in general practice wax is kept sealed, off the floor and away from heat. If cash is tight in a given month, a smaller order that keeps money for jars or marketing may be the right call even if the formula says otherwise. And if a supplier quotes a real per-kilo break for a larger order, the flat-price assumption no longer holds, and A 25 Kg Wax Pack Is Cheaper per Kg than 10 Kg — How Do I Decide Whether the Savings Justify Spending More Cash Upfront? is the page to use.

At 10 kg a month the stakes are moderate. The whole spread between the worst and best order sizes in the table is a few thousand rupees a year at most, against ₹60,888.00 of wax. That is worth getting right, but it is not worth overriding a real constraint for. Get the order size roughly right, set a clear trigger, and put the rest of your attention on wax lost to pour waste and rejects, which costs the same whatever size bag it came from.

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