My BOM Predicted 100 Kg of Wax but Actual Consumption Was 104 Kg — How Do I Determine Whether the 4% Variance Is Reasonable?

Your 104 kg against a 100 kg BOM, as numbers

Your figures are the title's: a BOM of 100 kg of wax and an actual consumption of 104 kg, a variance of 4 kg or 4%. Everything else on this page is a labelled worked example built around them, so you can lay your own run over it line by line. The worked order is a wedding favour run: 1,075 saleable favours plus 12 planned extras (6 QC retains and 6 burn-check candles), 1,087 candles in all, each 100 g at 8% fragrance on the total-weight basis, which is 8 g of Jasmine and 92 g of Luxury Soy Wax CSI 464. The BOM was recipe × candles: 1,087 × 92 g = 100.00 kg of wax. No reject line, no heel line, no top-up line. That detail decides the answer.

Notice what the worked order already tells you. The run poured 1,113 candles to keep 1,087, because each of the 26 rejects was replaced. That alone put 2.39 kg of wax into candles that were not kept. Some of it came back (1.08 kg from the 14 rejects that were dug out and remelted), some did not. A BOM with no loss line cannot see any of this, so a positive variance was certain before the first melt. The question is whether 4 kg is the right size for the losses this process really has.

If your BOM did include a loss allowance, the logic is the same but the arithmetic shifts: subtract the allowance first, then split what is left. A BOM that already carried a 3% loss line and still came in 4% over has a 1% gap to explain, which is a different conversation from this one. Write the BOM's own lines next to your actuals before you start.

Expected, avoidable, unexplained: the three-way split

The split uses things you can weigh or count after the run: the reject log, the number of melts, the heel you scrape back, the top-up pot you throw out at the end of each day, and a check-weigh of finished candles. The full list of places wax goes, and how to measure each one, belongs to the post on production losses to investigate. This page takes the measured results and asks the reasonableness question.

Expected: the BOM's missing loss line

Rejects, heels and top-up leftovers happen on every run of this process. They are the cost of doing it, and they belong in the BOM as a loss line, the same way a tailor buys more cloth than the garment weighs. Here they come to 2.66 kg, 2.66% of the BOM. Two of them can be shrunk without changing the candle. A warm pitcher scraped back into the next melt returns most of its heel; only the last melt of a scent really loses it. And the top-up pot can be sized to the day: if you top up about 1,087 favours over 6 days, a smaller pot reheated twice wastes less than a large one poured from once. Rejects are the line to leave alone here. Cutting the reject rate is a quality project, not a BOM tweak, and the reject arithmetic for a purchase plan is in the post on building a 4% reject rate into purchasing.

Avoidable: two lines with a fix each

Overfill is the line that surprises people. A favour that weighs 100.6 g instead of 100 g looks perfect; nobody can see 0.6 g. Multiply it by 1,087 and it is 0.60 kg of wax and about 52 g of oil. The fix is a fill line on the jar or a check-weigh of the first five candles from each pitcher, not a bigger BOM. Spills are similar: one bad spill a run is common, and it should be weighed into the log on the day rather than discovered as variance at the end. Do not budget avoidable lines in the next BOM. Fix them, and keep a small cushion for the unexplained instead.

Unexplained: the only part you are really judging

After everything you can name, 0.49 kg is left: 0.49% of the BOM. Where could half a kilo hide in a 104 kg run? In a scale that reads a few grams light on every 9.2 kg issue, in heels estimated on 4 melts and assumed for the other 8, in rejects remelted twice and logged once, in a bag that was not quite 10 kg. None of those is worth chasing at this size. That is why the threshold sits at 1%: below it, the remainder is inside measurement noise for a small workshop; above it, there is probably a real cause you have not found.

The whole split takes about an hour with the logs in front of you, and most of that is the check-weigh. If you kept no reject log and never weighed a heel, you cannot do it after the fact; the honest answer then is "unknown", and the per-batch log in the post on tracking consumption after every batch is how you make sure the next run can be judged.

Why "reasonable" depends on your process

Expected losses are set by how you make candles, not by a universal percentage. To show how much they move, here is the same 1,087-favour order computed for five set-ups. Every input is a labelled worked example; the point is the spread, and the method you can repeat with your own numbers.

Three things follow. First, the number of heels matters as much as their size: 52 small pots leave more wax behind than 12 big melts, even with a smaller heel each. Second, scent changes cost a clean-down each, so a three-scent run should carry a bigger loss line than a one-scent run of the same size. Third, a variance below the expected line is not automatically good news. In set-up E, a 4% overrun against 4.87% of expected losses means the candles used less wax than they should have, and the most likely explanation is underfilling. If your label declares a net weight, that is a compliance question as well as a client one; check current requirements for packaged goods (this is practical judgement, not legal advice).

Scale changes the picture too. A loss that is fixed per melt, such as a heel, shrinks as a percentage when the melts get bigger and the run gets longer; a loss that is fixed per candle, such as overfill or a top-up, does not. That is one reason a formula that looked thrifty in 1 kg trials can look wasteful at production scale, and the reverse. The cost-reduction post on hidden losses at production scale works through that effect on margins; here it is enough to know that your band should be rebuilt whenever the batch size or the number of scents changes.

What the 4 kg cost, and what it nearly cost

At CSI live pricing on 7 October 2026, Luxury Soy Wax CSI 464 is ₹507.40 a kilo at every size from 1 kg to 10 kg. The 4 kg is worth ₹2,029.60, or ₹1.89 per saleable favour. The wax was not lost on its own, though. Rejects, heels, top-up pots, overfill and spills were all scented mix, and every 92 g of wax in that mix carried 8 g of oil. So the 4 kg took about 348 g of Jasmine with it, ₹1,364.52 at the 1 kg per-gram price, which is why the oil line on a run like this usually overruns by a similar percentage. Wax and oil together: ₹3,394.12, ₹3.16 a favour.

Seen that way, chasing the unexplained 0.49 kg is worth ₹246.58 of wax. An afternoon spent hunting it costs more than it saves. The avoidable line is worth more (₹431.30 of wax plus its oil) and has a one-minute fix, so that is where the effort goes.

The real cost: a top-up in the middle of a wedding order

The worked run bought the BOM as 10 × 10 kg (₹50,740.00) and ran out of wax on day 6 with about 40 favours still to pour. The 4 × 1 kg top-up cost ₹2,029.60, exactly the same per kilo, because CSI 464 is flat per kg. The money was never the risk. The risks were the day lost waiting for wax with a wedding date fixed, and the top-up arriving as a different wax lot in the last melt of the order. For a favour that sits on a table next to 1,074 others, a visible difference in the last 40 is a complaint. How to calculate the remaining requirement before production stops is the hub post, the post on running short of wax mid-production; checking a new wax lot before it goes into an order is the post on managing multiple wax lots.

Commercial protection (practical judgement, not legal advice): the client never sees your variance, but they will see the consequences. Price the next favour order from the corrected BOM, not the recipe, so the loss line is paid for. If a family changes the fill weight, the jar or the quantity after approval, that is a new BOM; put a line in your written order that changes after approval are re-quoted, and that the advance covers client-specific materials. The worked 4% overrun cost ₹3,394.12; an unpriced change of jar can cost far more.

The next BOM: a loss line, not a guess

The next favour order of the same size gets a BOM that carries the expected losses measured on this one, plus a small cushion for the unexplained, and nothing for the avoidable lines, because those are being fixed. On the series' purchase-sheet pattern (required → planned extras → loss buffer → pack rounding → final order and leftover):

The loss line works out at 3.2% of the recipe wax. Compare it with the old BOM: 100 kg of wax and 8.696 kg of oil, with nothing for loss. The new one would have covered this run without a top-up, with 0.83 kg to spare. If you have not fixed the overfill and the spill habit by then, carry them too: the wax to cover becomes 104.02 kg, bought as 105 kg (₹53,277.00). That is the honest cost of not fixing them.

Argued against our own interest: do not respond to a 4% overrun by adding 10% to every future BOM. On 100 kg of wax that is 10 kg you will mostly not use, and a buffer that big hides the next real problem by absorbing it. Add the measured expected loss, keep the cushion small, and re-measure on the next run. How to turn one run's variance into a standing loss percentage per material, and when to trust it, is the post on incorporating a historical variance into future BOMs; the full post-order review that feeds your next quotation is the post on comparing estimated and actual consumption.

What must not be skipped next time, and how long it takes

Three habits make the next variance judgeable. A check-weigh of ten candles from each melt (a few minutes a melt). The heel weighed back into a tared pitcher at every melt (seconds). A reject log that records what happened to each reject's wax (a line each). Add one calendar item: if the order is split across two wax deliveries, the second lot gets a side-by-side check before it is mixed into the order. Pour three candles from each lot, compare them set the next day, and burn them once they have had the 48-72 hours of cure that Jasmine's page states: about three calendar days, which must be inside the plan, not discovered at the end of it.

Finally, write the corrected BOM somewhere you will find it when the next enquiry arrives in wedding season, commonly November to February, when quotes go out quickly. A favour quote built on recipe × candles will be short again by roughly the same 2.66%, and you will be buying a top-up in the same week as everyone else.

The wax, the oil and the two tools behind the split

Chosen on page statements, price and stock on 7 October 2026. The wax and oil are the worked order's; the pitcher and scale are what turn heels and overfill from guesses into weighings, which is what makes the split possible.

The honest summary: a 4% variance on a recipe-only BOM is usually reasonable and always informative. You need no new equipment to judge it, only a reject log, a weighed heel and a ten-candle check-weigh. Buy the pitcher or scale only if you do not already have something that does the same job.

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