What’s your usual price? Keeping a grocery price book from your receipts

Is $3.49 a good price for this coffee? The tag says it was $4.99, so the store thinks so. The question you actually have is a different one: is it less than we usually pay? Nothing on the shelf answers that.

Careful shoppers have an old answer to it, the price book: a notebook or a spreadsheet of what you pay for the things you buy most. Nearly every guide to keeping one starts the same way, by telling you to get your receipts out, and then asks you to copy them by hand. That’s where most price books stop. Below is how to build one that’s worth the copying, and how to read it once you have it.

What the sale tag is comparing against

The “was” price on a tag, the “regular price” line on your receipt and the “you saved” total at the bottom all compare today’s price with the store’s own reference price. The Federal Trade Commission’s guides on pricing say a former price used this way should be one the item was actually offered at “on a regular basis for a reasonably substantial period of time” (16 CFR 233.1). Those are guides for sellers, not a guarantee you can hold a store to.

And even an honest regular price only measures the discount. It says nothing about whether today’s price is low for you, which is the thing you wanted to know.

What “usual” should mean

Your usual price for something is what you paid for the same product, in the same size, at the same store, over your last few purchases. Each part of that matters.

• The same size. A 12-ounce bag at $7.99 and a 24-ounce bag at $13.99 aren’t comparable prices. If the size changes, compare per ounce or per pound.
• The same store. The point is to know your own price, not the market’s.
• More than one purchase. One purchase is a price. Two show a change. Around three, you can start calling it usual. A blank is better than a “usual” built on a single receipt.

Building one from the receipts you already have

1. Pick ten to fifteen things. The ones that repeat across your receipts: the coffee, the milk, the eggs, the cereal, the detergent. A price book of two hundred items is a price book nobody reads.
2. One row per purchase, with a column each for the date, the store, the item as the receipt printed it, the size, the quantity, the price you paid, and the regular price when the receipt prints one.
3. Keep the price you paid and the regular price apart. Never write down the saving instead of the price, or the regular price minus the saving. Take this Safeway line:

HONEY NUT CEREAL          2.50 S
Regular Price      4.29
Card Savings       1.79-

The row gets 2.50 as the price paid and 4.29 as the regular price. Mix the two up once and every comparison after it is quietly wrong.

4. For anything sold by weight, write the price per pound, not the line total. Three pounds of apples and two pounds of apples are the same price if the rate didn’t move.
5. When the receipt prints a quantity, divide by it. When it doesn’t, don’t assume one; leave a note. A line that says 6.98 might be one item or two.

If you’d rather not start from a blank page, the free grocery spending template has a Prices sheet that lists every price you’ve paid for one product, dated.

Reading it

Once there are a few rows per item, a sale is easy to judge. If today’s price is below your usual, it’s a good price for you, whatever size the tag says the saving is. If the “sale” price is about what you normally pay, it’s your regular price with a sign on it.

The pattern only a price book shows

Here’s one from our own records. It’s a 100-gram bar of dark chocolate, bought at the same supermarket in Portugal, so the prices are in euros. The country doesn’t matter to the point, which is about arithmetic.

Eleven of the receipts it’s on printed a quantity, over nine months. Ten of those eleven carried a discount.

The discount kept its proportion the whole way. Every one of those receipts printed a saving of about the same size, and every one was accurate, while the price actually paid went up by more than a fifth. Each receipt said we’d saved money. None could say the price we were saving on was rising. That only shows up when the rows sit next to each other.

What a price book can’t tell you

• Whether another store is cheaper this week. That’s a different question, and comparison tools exist to answer it.
• Anything about things you’ve bought once.
• A price per ounce when the receipt printed no size and you didn’t write it down. Then you can only compare the same pack against itself.

A price book that fills itself in

A price book is only as good as the receipts behind it, and copying them out is where most of them die. CartEncore reads each receipt and keeps the price you paid and the store’s regular price as separate numbers, for every line. Once there are three comparable purchases of something, it shows your usual price for it. It won’t tell you where to shop, and it doesn’t count your savings.

One product’s prices over time, in more detail: what one product has cost you →
When a price looks wrong at the register: how to check your receipt →