How to use the bulk buy savings calculator
- Enter the regular pack price and how many units it holds.
- Enter the bulk pack price and its units. Use the same kind of unit for both, such as rolls, cans or ounces.
- Enter the units you will really use before the product spoils, expires or you stop wanting it.
- Read which option costs less, the cost per unit used, the units left unused and the use needed for bulk to match the regular price.
Formula
packs = units needed / units per pack, rounded up
cost = packs x pack price
cost per unit used = cost / units used
break-even use = bulk price / (regular price / regular units)
The break-even use is how many units a bulk pack must serve for its price to equal the regular price per unit. Below that, the bulk pack costs more per unit used.
Six-packs against a bulk pack of 36
A regular pack of 6 costs $4.50, or $0.7500 a unit. A bulk pack of 36 costs $24.00, or $0.6667 a unit. To use 24 units, you buy 4 regular packs for $18.00 or one bulk pack for $24.00, so the regular packs save $6.00, shown as ($6.00) from the bulk side. The bulk pack leaves 12 units unused, worth $8.00.
The break-even use is $24 / $0.75 = 32 units. Using all 36 makes bulk save $3.00. To use 40 units, regular packs cost 7 x $4.50 = $31.50, while bulk needs two packs at $48.00 and leaves 32 units unused.
The cheaper unit price is not the whole story
A lower price per unit only saves money on the units you use. If you pay $24 for 36 and use 24, you paid $1.00 for each unit that you used, more than the $0.75 a unit at the regular pack. The unit price compares products, while the cost per unit used compares what you actually spend. This page shows both so the difference is clear.
Food that spoils, products that expire, and items you will not need after a move or a change of habit are the usual cases. A product that keeps for years and that you use steadily is the best fit for a large pack, and the unused units then still have value for later.
Using the break-even
The break-even use is the simplest test. If you expect to use at least that many units from the bulk pack, it beats the regular price per unit. If you are unsure, compare it with your own history: how many units did you use in the last few months? Storage space, a membership fee for a warehouse club, and the cost of tying up money are not modeled, so adjust the prices if they matter.
The Unit Price Calculator compares up to six products by unit price, the Shrinkflation Calculator spots a smaller package at the same price, the Cost per Use Calculator spreads a price over uses, and the Price Match Calculator helps with a lower price elsewhere.
Assumptions and limits
- Prices are in dollars and cents. Units in a pack and units used are above zero and may have decimals.
- Both packs use the same unit. Whole packs are bought, so a partial pack is rounded up.
- Unused units are counted as lost. If you would use them later, treat the result as the cost for now.
- Storage, shipping, memberships and spoilage beyond the units you enter are not modeled. Nothing is stored or uploaded.
Frequently asked questions
Is it cheaper to buy in bulk?
Only if you use enough of it. The bulk pack has a lower price per unit, but you pay for every unit, so unused ones raise the cost per unit used. The break-even use shows how many units you must use.
How do I calculate the break-even for a bulk pack?
Divide the bulk price by the regular price per unit. With $24 for the bulk pack and $0.75 a unit at the regular size, the break-even is 32 units.
What if I will use the extra later?
Then the unused units are not wasted, and the bulk pack may be the better buy. Enter the units you will use before the product spoils for a cautious view, or all units for an optimistic one.
Why round packs up?
Because you cannot buy part of a pack. To get 40 units from packs of 36 you must buy two, and the extra 32 units count as unused. The page shows that so you can see the real cost.