Start with usable yield, round purchases to packs and plan replenishment. Start with repair orders, parts invoices and technician time logs. Each example below uses hypothetical values you can replace.
Usable Material Cost
Account for cutting waste or unusable stock before pricing delivery.
Cost per usable unit = purchase cost / (purchased units × usable share)
Show example inputs and result
| Purchased material cost | 1,000 |
|---|---|
| Purchased units | 100 |
| Usable share | 90 % |
Result: 11.1111 per usable unit.
Yield must be greater than zero. Keep purchased and usable quantities in the same measurement unit.
Open usable material costMaterial Order in Whole Packs
Round a material requirement to actual purchasable packs.
Packs = ceiling(net quantity × (1 + waste) / pack quantity)
Show example inputs and result
| Net quantity needed | 86 |
|---|---|
| Waste allowance | 10 % |
| Units per supplier pack | 12 |
Result: 8 packs.
Apply waste before rounding. The allowance adds to net need; it is not a percentage loss from purchased quantity.
Open material order in whole packsInventory Reorder Point
Estimate a replenishment trigger from entered usage and lead time.
Reorder point = daily usage × lead time + safety stock
Show example inputs and result
| Average daily item usage | 8 |
|---|---|
| Supplier lead time | 7 days |
| Safety stock | 20 items |
Result: 76 items.
The trigger says when to reorder. Purchase quantity also depends on supplier minimums, stock space, and demand variability.
Open inventory reorder pointEconomic Order Quantity
Balance order frequency and stock holding under steady demand.
EOQ = square root(2 × annual demand × ordering cost / annual unit holding cost)
Show example inputs and result
| Annual unit demand | 1,200 |
|---|---|
| Cost to place one order | 40 |
| Annual holding cost per unit | 6 |
Result: 126.4911 units per order.
Assumes constant demand and lead time, no quantity discounts and no stockouts. Round to supplier pack sizes separately.
Open economic order quantityInventory Turnover
Measure how many inventory equivalents were consumed during a period.
Turnover = period cost of goods / average inventory
Show example inputs and result
| Cost of goods used or sold in period | 120,000 |
|---|---|
| Average inventory at cost | 20,000 |
Result: 6 turns per period.
Comparing revenue with inventory cost mixes measurement bases and inflates the apparent turnover.
Open inventory turnoverSupplier Switching Savings
Compare recurring savings from an alternative supplier.
Monthly savings = volume × (old unit cost − new unit cost) − extra recurring cost
Show example inputs and result
| Monthly purchased units | 200 |
|---|---|
| Current cost per unit | 20 |
| Alternative cost per unit | 18 |
| Extra monthly shipping or service cost | 100 |
| One-time switching cost | 500 |
Result: 300 per month. Setup cost to recover separately: 500
Shipping, defects, delays, and switching work can offset a lower purchase price. Enter known additional costs.
Open supplier switching savingsUse the results in your plan
For a auto detailing business, review consumables, technician hours, and bay occupancy across the complete workflow. Use one consistent period and delivery unit: a detail package. Compare the assumptions with recorded outcomes after delivery, then update the estimate.
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