Spare parts consumption calculator

The steady rule is the classic normal model: safety stock = z × sample deviation × √lead time, reorder point = mean lead-time demand plus that stock. That model quietly assumes demand is roughly symmetric; spares issued a few times a year are not, so the lumpy mode drops the probability claim and stocks the worst observed period across the whole lead time instead. EOQ assumes consumption runs at a steady rate between orders, which lumpy demand also breaks. Everything is computed from the history you paste, in this tab; nothing forecasts future failures and nothing is uploaded.