Weighted average, in the words of a factory owner
Why your steel has one honest price even when you bought it at three.
You bought plate three times this quarter: at ₹48, at ₹50, at ₹53. Today the floor takes 200 kg. What did that steel cost?
Whoever answers from memory picks the number that suits the argument. The purchase manager remembers ₹48. The costing sheet says ₹53. Both are quoting a real bill. Both are wrong.
One tank, one price
Think of diesel in a tank. You filled it at ₹90 and again at ₹95. The litre you burn now is not “a ₹90 litre” or “a ₹95 litre” — the tank mixed them. The honest price is the average, weighted by how much went in at each rate.
Steel on a shelf works the same way. There is no “that pallet” once stock mixes — there is one pile, with one running value.
Why it must be automatic
The average changes on every purchase. Kept by hand it is stale by Tuesday — so the person costing a job reaches for whichever bill is on top.
In SutraBook the running average is written by the same entry that receives the goods. Stock out — to a run, a van, a repair — always leaves at that average. Gross margin stops being a matter of opinion.
The one rule to remember
Nobody types a cost on the way out. If someone can, the same steel leaves at one price on Tuesday and another on Wednesday, and the difference quietly becomes profit that never existed.
That is the whole system: value moves only with goods, at one honest number.