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Grocery price detective

You're going to the store anyway. This time your kid gets five items on the list to investigate, a pencil and the small print on the shelf tag, and they come home knowing how to tell which box is really the better deal.

Dad Field Manual editors · Drafted with AI help · Published Oct 15, 2026
Tested on: not yet. When a dad tries this, his name, the date, the place, and the kids' ages go here.

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Time
60 min
Cost
$0
Ages
7 to 12
Where
Your grocery store

01What you need

  • Your normal shopping list, with five items circled for the detectiveHave
  • A detective sheet: an index card or paper with five rows, item, choice A, choice B, winnerHave
  • A pencil and something to write on, like a clipboard or a cereal-box backHave
  • A phone calculator for when there's no unit price on the tagHave

Where: The store you already shop at, on your normal trip. Quieter hours make it easier to stop and read tags.

Store safety: read this first

  • No riding or climbing on the cart, on the sides or the front, and no pushing a cart with a younger sibling in it. Carts tip.
  • Pick a meeting spot by the registers before you split up, even for one aisle. Kids under 10 stay in the same aisle as you.
  • Grown-ups get the high shelf and the glass jars. Detectives point; they don't pull a heavy thing down over their heads.
  • Watch the aisle traffic. Stand to the side to read tags so carts can pass.

02Steps

  1. Brief the detective at home

    DadCircle five items on your list that come in more than one size or brand, like cereal, peanut butter, rice, paper towels and yogurt. Say: "Your job is to find out which one gives us the most for our money. The clue is on the shelf tag."

  2. Find the unit price

    Dad showsKid copiesAt the first item, crouch down to the shelf tag under the product. Point to the big number: "That's what this box costs." Then the small number: "That's the unit price, what it costs per ounce. It lets us compare a little box and a big box fairly."

  3. Compare two choices

    KidFor each circled item, the detective picks two choices, like the big box and the small box, or the name brand and the store brand. They write both unit prices on the sheet and circle the lower one.

  4. Solve the tricky cases

    TogetherSometimes there's no unit price, or one tag says per ounce and the other per pound. Then do the math on the phone: price divided by size. Check sale tags too, since they should show a unit price. Ask: "Is the sale really cheaper per ounce than the big regular box?"

  5. Make the call

    KidThe cheapest per ounce isn't always the right buy. Ask: "Will we use the giant jar before it goes bad? Does anyone actually like that brand?" Let the detective decide which goes in the cart and say why.

  6. Close the case at home

    TogetherAt the kitchen table, look at the sheet. Ask: "How many times was the bigger size cheaper? Did the store brand win?" Sign their field card when they've solved all five.

03If it stalls

  • If they get bored after two items, stop at two. Next trip, do the other three.
  • If the small print is hard to read, especially on the bottom shelf, take a phone photo of the tag and zoom in.
  • If they want the most expensive one because it has a cartoon on it, write that down too and compare. Then let them use their own money if they still want it.
  • If you're in a hurry, give them one item and the whole aisle while you shop nearby.

04Variations

Ages 7–8

Two or three items, and only the bigger-or-smaller question. You read the tag; they find which number is lower.

Ages 9–12

All five, plus one case with no unit price where they divide price by size themselves. Add a challenge: guess the winner before reading the tag.

Online order

If your store's website or app shows a unit price next to each item, use the same sheet and the same five items on the couch before you order. If it doesn't, they divide price by size.

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05Sources

  • What a unit price is and where it goes. NIST's Unit Pricing Guide defines unit pricing as the cost per unit of measure, such as per ounce, calls it one of the best tools for comparing value across pack sizes, says the shelf label should sit directly above or below the product, and says sale tags should show unit prices too. National Institute of Standards and Technology Checked Oct 15, 2026
  • Not every store posts unit prices. The same guide says unit pricing is voluntary unless state law requires it, that 16 states and three territories have unit pricing laws or regulations, and that shoppers complain bottom-shelf labels are hard to read. National Institute of Standards and Technology Checked Oct 15, 2026
  • Kids and comparison shopping. The CFPB's middle-childhood handout says kids ages 6 to 12 begin to understand comparison shopping and suggests teaching them to comparison shop in stores and online and letting them help with money decisions. Consumer Financial Protection Bureau Checked Oct 15, 2026
  • Shopping cart falls. CPSC's shopping cart safety alert says falls from carts are among the leading causes of head injuries to young children, and says not to let a child ride or climb on the sides or front of the cart, or push a cart with another child in it. U.S. Consumer Product Safety Commission Checked Oct 15, 2026

Filed under: Money

Dad Field Manual · Field card 07 · MoneyIdea · not yet tested

Grocery price detective

You're going to the store anyway. This time your kid gets five items on the list to investigate, a pencil and the small print on the shelf tag, and they come home knowing how to tell which box is really the better deal.

Time
60 min
Cost
$0
Ages
7 to 12
Where
Your grocery store

What you need

  • Your normal shopping list, with five items circled for the detective
  • A detective sheet: an index card or paper with five rows, item, choice A, choice B, winner
  • A pencil and something to write on, like a clipboard or a cereal-box back
  • A phone calculator for when there's no unit price on the tag

Store safety: read this first

  • No riding or climbing on the cart, on the sides or the front, and no pushing a cart with a younger sibling in it. Carts tip.
  • Pick a meeting spot by the registers before you split up, even for one aisle. Kids under 10 stay in the same aisle as you.
  • Grown-ups get the high shelf and the glass jars. Detectives point; they don't pull a heavy thing down over their heads.
  • Watch the aisle traffic. Stand to the side to read tags so carts can pass.

Steps

  1. Brief the detective at home. Circle five list items that come in different sizes or brands and give them to your detective.
  2. Find the unit price. Find the small unit price on the shelf tag, which shows the cost per ounce, pound or count.
  3. Compare two choices. For each item, write two unit prices on the sheet and circle the lower one.
  4. Solve the tricky cases. If a tag has no unit price, divide the price by the size on the phone calculator.
  5. Make the call. Let them choose which one goes in the cart and say why, not just which is cheapest.
  6. Close the case at home. Count how often bigger or store brand won, then sign their field card.

If it stalls

  • If they get bored after two items, stop at two. Next trip, do the other three.
  • If the small print is hard to read, especially on the bottom shelf, take a phone photo of the tag and zoom in.
Cases solved (of 5) · times the big size won
Signed off: can do this.Signed by Date

dadfieldmanual.com/plans/price-detective · Sources: National Institute of Standards and Technology, Consumer Financial Protection Bureau, U.S. Consumer Product Safety Commission