Inventory & Stock Cost: Know Your Real Margin, Not a Guess

Rose's Hair Studio in Kajang sells retail shampoo and serum at the counter alongside haircuts. Every month Rose buys a case of 24 bottles at wholesale price, puts them on the shelf, and sells each one for RM35. At month-end, when she tries to work out how much the retail side actually made, she's guessing — she knows the case cost RM480, but not how many bottles were really sold versus lost, broken, or handed out free to a regular.

Auto Hafiz Workshop in Seremban buys engine oil by the 20-litre drum, and a typical service uses about 4 litres. Hafiz charges customers RM25 a litre, but has never worked out the actual cost per litre once spillage and waste are counted in — he just rounds it in his head.

Titian Wangi Spa in Ipoh goes through facial masks and massage oil in every session — these materials aren't sold, they're used up during the treatment. The owner charges RM120 per facial, but has never worked out how much the mask and oil actually cost per session — so she doesn't really know how much the service earns.

Why this keeps happening

First: cost arrives in bulk, but gets sold or used one unit at a time. Buy a case, sell a bottle. Buy a drum, use a litre. The real per-unit cost never gets calculated — it just gets rounded.

Second: there's no signal before something runs out. The owner or staff find out when the shelf is empty and a customer is already standing at the counter, not before.

Third: waste, breakage and shrinkage go unrecorded. When the physical count doesn't match what should be on the shelf, there's no record of where the difference went.

Fourth: materials used during a service never enter the cost calculation at all. The service margin looks healthy in your head, while the material cost is quietly eating a good chunk of it.

What owners try instead

Most common: a tally in a notebook for every bottle sold. It works with one staff member on the counter, but with two, two notebooks give two different answers.

Some rely on eyeballing the shelf. Good enough for a small operation, but you can't check it remotely, and it gives no warning before an item actually runs out.

Some lump every supply purchase into one general "Supplies / Stock" expense category. It shows up in the reports as one big number a month, but never breaks down into a per-unit cost or margin for any single item.

The riskiest: guessing the margin by feel — "after costs, it must be profitable" — until the day someone actually does the math and finds wholesale prices crept up months ago while the sell price never moved.

How stock cost should work

TempahKu has an Inventory module for this — but one honest note first: it has to be switched on (POS must be enabled first), and you need to ask TempahKu to turn it on for your account. It isn't a toggle that's open by default.

First principle: every item is tagged one of two kinds — "Sold" for things that go through the POS counter, or "Used" for materials consumed during a service, like facial masks and massage oil. Both kinds carry a cost, but only "Sold" items appear on the POS sell screen — so a service material can never get rung up as a product by mistake.

Second principle: the per-unit cost is calculated by the system, not guessed. When you tap "Receive stock" and enter the quantity and purchase price — say a case of 24 bottles for RM480, or a 20-litre drum — the system works out a weighted-average unit cost on its own. Buy the same item at a different price next time, and the average adjusts itself; you never do that math by hand.

Third principle: you set a low-stock threshold per item, and once the quantity hits that number (or runs out completely), the item is flagged directly in the "Inventori" list. The main dashboard also shows a warning card that links straight there whenever any item needs it — so you see it before the next customer asks, not after the shelf is bare.

Fourth principle: for "Sold" items, stock deducts itself every time one is rung up at the POS — you never update it manually after a sale. This part needs honesty too: "Used" items like facial masks or massage oil are not auto-deducted per booking in the current version — you still update those quantities by hand when you take material out of stock for a session.

Fifth principle: cost and stock value flow straight into your Reports. "Stock cost (COGS)" feeds directly into your Profit & Loss, and "Stock value on hand (asset)" shows how much money is currently sitting on your shelves — two numbers an owner previously had to work out by hand, if at all.

When it helps most

It matters most for businesses that sell physical products alongside a service — a salon selling retail shampoo at the counter, a workshop billing engine oil by the litre, anywhere a bulk purchase needs converting into an accurate per-unit cost.

It's also useful for businesses that go through a lot of valuable consumables — facial masks, massage oil, single-use supplies — where the material cost, left untracked, quietly eats into the service margin without anyone noticing.

If your business only sells two or three kinds of products and you're the one buying and stocking the shelf yourself, or if your business is pure service with no physical product sold or used up — tuition, photography, an at-home service that consumes nothing — you don't need this yet. A simple mental count or a small spreadsheet is still enough. And because it has to be switched on rather than turning itself on, don't wait for it before you start selling products — start simple, and ask for it once your product list has grown large enough that doing the math by hand has become the actual bottleneck.

In short

The difference between guessing your margin and knowing it isn't about being more diligent with arithmetic — it's about where the cost gets recorded. When a bulk purchase never gets converted into a per-unit cost, every margin you quote is a guess that sounds like a number.

TempahKu's Inventory module calculates a weighted-average cost automatically every time you receive stock, flags items that need reordering before they actually run out, keeps sold products separate from the materials used up during a service, and sends cost and stock value straight into your Profit & Loss report. If you've ever worked out a product's profit in your head and weren't sure the answer was right, that alone is reason enough to try it.