A multi-buy can lower the price of each package while raising the amount you pay today. Before calling it a saving, ask two questions: how many packages did you intend to buy, and what conditions unlock the offer?

Create your grocery plan in Piggy with a manual target and expenses you explicitly record. No account or app download is required. For the separate like-for-like example below, open the editable calculator; it starts with coffee defaults, which you must replace.

Prepared with AI assistance and editorial checks. All prices, quantities and shopping routines in this guide are fictional USD examples, not offers from a real shop.

Read the condition before dividing the price

An offer might require two packages, a specific size, a membership, or an activated coupon. Do not assume one package qualifies for half the advertised bundle price. Check the actual conditions and the amount charged at checkout.

The Australian Competition and Consumer Commission explains that unit prices compare similar groceries using a standard measurement, and its Australian guidance also discusses offers of multiple identical items for one price. Read the ACCC guidance, checked October 27, 2026; no publication date is shown on the page. We use that comparison principle here, not its jurisdiction-specific display rules as a statement of law elsewhere. It does not endorse Piggy.

One planned package is not the same basket as two

Suppose an identical 400 g pantry product normally costs USD $2.50 for one package. A fictional offer is two packages for $4.00, and the offer requires buying both. Assume equivalent product specification and net contents, consistent tax-inclusive prices, no fees, no other discounts and no membership cost.

The offer works out to $4.00 ÷ 2 = $2.00 per package. If you already intended to buy two, the comparison is $5.00 versus $4.00: $1.00 less for the same basket.

If you intended to buy only one, however, checkout is $4.00 instead of $2.50: $1.50 more today. You also get another package. That is not a like-for-like $1.00 saving on your original basket. Neither number decides the purchase for you: check cash available, storage and whether the extra package has a useful place in your plan.

Treat stock-up timing separately from consumption

Buying an extra package this week might replace a later purchase; it might also leave something unused. Do not count a future avoided purchase until it actually happens, and do not record the same package again when you use it. Keep a simple note of the quantity on hand and the purchase it is expected to replace.

Choosing one package can be sensible even when two have a lower unit price. A spending target is not a bank balance, and a lower unit price is not permission to leave an upcoming bill unfunded. You do not need to share your personal amounts to use this check.

The supported experiment: hold two packages constant

For a separate planning scenario, assume you buy two identical 400 g packages once per week, at a previous price of $2.50 each versus a scenario price of $2.00 each, for 52 weeks. Assume that hypothetical offer remains available and that you qualify each time. This is not a forecast or a suggestion to buy that often. Taxes, fees and discounts stay on the same basis described above.

($2.00 − $2.50) × 2 × 1 = −$1.00 per week. Annual projected cost changes from $260.00 to $208.00, a $52.00 decrease, or $4.33 less per average month after rounding. The unrounded monthly difference is $52 ÷ 12.

If the offer applies for only one shop, the comparable two-package difference is just $1.00 for that shop—not $52.00. If only 10 qualifying shops occur, the difference is $10.00. The calculator annualizes the routine you enter; it does not know offer expiry, stock levels or later purchases.

Reproduce it without changing the basket

Open the coffee preset and select USD and same-size package. Replace Previous price with 2.50, Scenario price with 2.00, Units per purchase with 2, Purchases per period with 1, and Repeat period with Week. Leave the optional monthly target blank. Confirm comparable product size and consistent tax, fee and discount treatment only after checking those assumptions.

We reproduced $4.33 less per average month, $1.00 less weekly and $52.00 less annually in the live calculator on October 27. Unchecking the comparability confirmation blocks results. The calculator holds quantity constant: it cannot model one package versus two, decide whether a coupon applies, convert package sizes or check a real offer. The earlier one-versus-two checkout comparison is separate hand arithmetic.

Record what you paid, not the advertised saving

In a purchase record, enter the actual total paid. Do not subtract the promotion's claimed saving again. If a receipt shows two packages and a separate discount, review how the final amount reconciles before copying it into a spreadsheet; leave unclear quantities unknown instead of guessing.

Piggy's receipt-to-Excel tool is separate from the scenario calculator. Its web beta handles one selected photo per workbook, with English OCR that needs your review and the selected receipt picture embedded in the XLSX. It does not validate promotion eligibility, read your bank or determine complete household spending. Optional budget saving is browser-local, not cloud backup.

Your takeaway: compare the basket you actually need

Read the conditions, compare identical quantities, then check the checkout amount against your plan. A good per-package price and a manageable purchase today are different questions.

Create your manual grocery plan, or try the same-two-package calculator example using the inputs above. Piggy is live on the web in Safari and Chrome without an app download; the native iPhone app is separately coming soon.

Sources and coverage

Evergreen multi-buy comparison, not merchant-price news, legal advice or guaranteed savings. Fictional USD prices include consistent taxes and exclude fees and other discounts. Same-size fixed-quantity scenario only; one-versus-two checkout comparison is hand arithmetic. No private receipts used.

A little clarity, not a guarantee

Projections are not recorded spending or confirmed savings. No national average or future price is inferred. The web calculator does not upload receipts, send family requests, or update the iPhone app.