Calculate a multibuy price only for a basket that qualifies
Separate eligible and ineligible baskets before calculating a multibuy unit price, using explicit fictional terms and the amount actually charged.
A multibuy price belongs to a qualifying purchase, not automatically to every pack beside the sign. Before putting a discounted figure in your shopping comparison, write down which products and quantities activate it. A price calculated for two packs can mislead someone who intends to buy only one.
Define the practice offer completely
Consider a fictional offer in USD: buy two eligible 250 g oat packs for USD 4.50 in one transaction. One eligible pack costs USD 2.75. A 350 g variant costs USD 3.00 and is excluded. Assume this practice offer needs no membership or coupon, is currently valid, and has no additional taxes or fees. These are invented terms, not a live retailer promotion.
| Basket | Does this offer apply? | Amount for these goods |
|---|---|---|
| One eligible 250 g pack | No: only one eligible pack | USD 2.75 |
| Two eligible 250 g packs | Yes | USD 4.50 |
| One eligible pack plus the excluded 350 g variant | No: the second pack is ineligible | USD 5.75 |
The qualifying basket contains 500 g, so USD 4.50 divided by 500 and multiplied by 100 gives USD 0.90 per 100 g. A single eligible pack costs USD 1.10 per 100 g. Neither calculation allows you to buy one pack for half the multibuy total.
Keep the qualification next to the number
The NIST 2025 Unit Pricing Guide recommends presenting unit prices for the different pricing scenarios, including multiple-item prices. It is background best-practice guidance; it does not establish the terms of a particular shop's offer.
Write your own comparison as USD 0.90 per 100 g when buying two eligible 250 g packs together. That sentence preserves the condition. A bare USD 0.90 figure would leave out the purchase needed to obtain it.
Check the real basket before relying on the saving
- Match the size and variant to the eligibility wording.
- Check the offer dates, quantity requirements and any membership or activation steps.
- Keep a copy of the terms and inspect the checkout adjustment.
- If the expected discount does not appear, resolve it before treating it as received.
The FTC's online-shopping guidance advises reading deal conditions, including whether they require unwanted purchases. The lower unit price in this exercise does not establish that you need a second pack. Compare the cash outlay as well as the unit price.
For the food-label side of your choice, try Ingredi AI from the App Store or Google Play. Keep your receipt calculation separate from any ingredient interpretation; these links do not establish that the app checks live retailer promotions.