Advanced options
Bulk only saves on things you WILL use before they expire or bore you: the canon is loo roll, washing powder, rice, pasta, tinned goods, pet food, nappies in the current size only. The traps: unit prices on big packs aren't always lower (supermarkets know you assume they are: check the shelf-edge per-100g EVERY time), warehouse memberships need the fee earned back, and bulk perishables are just organised waste. Storage is a real cost in small homes.
What The Bulk Buying Calculator Works Out
- Unit price, normal vs bulk: each price divided by its size, in pence per 100 units (100g, 100ml or 100 items). The pack size decides nothing and the unit price decides everything; consumer bodies find larger packs carrying higher unit prices often enough that checking every time is the price of playing.
- Applied to your spend: the bulk discount percentage multiplied by your yearly spend on bulk-able items. A genuine 20% to 40% discount on the storecupboard canon compounds into a three-figure annual saving; if the big pack is dearer per unit the saving is zero and the small pack wins.
- The bulk-buying rules: stockpile only the boring and eternal (loo roll, washing powder, rice, pasta, tins, pet food, nappies in the current size), split big packs with neighbours, and make a warehouse membership earn its fee in savings that are genuinely additional to the offers you would have used anyway.
- Units you use per month and shelf life (advanced): how fast you get through the product and how many months before the bulk pack spoils, goes stale or stops being wanted. If the pack outlasts its shelf life, the share that would be thrown away is treated as waste.
- Months to use the bulk pack (advanced): your share of the pack divided by monthly use, and whether that beats the shelf life. Bulk perishables are organised waste wearing a discount; a six-month supply of something that lasts three is half a saving.
- Bulk unit price after waste (advanced): the shelf unit price divided by the share actually used, so the bin's cost shows up in the comparison. A 30% discount with 40% wastage is a loss.
- Membership and delivery (advanced): the warehouse club fee (typically GBP 35 or so a year) plus delivery or fuel for each bulk order or trip, as a yearly total to set against the saving.
- Households splitting the pack (advanced): sharing a warehouse trolley with family or neighbours gets bulk prices at retail quantities, which shortens the time to use your share and dissolves the storage problem.
- Net saving per year (advanced): the saving after waste minus membership and delivery, which is the only figure that says whether bulk buying is actually paying you.