Shake the bag. The best deal always rises to the top.
We compare Halloween candy prices per 100 g across Amazon and 9 grocery chains, every morning. Then we let physics pick the deal of the day.
Coupon of the week: SPOOKY12Stack it on any bulk bag over 1 kg at our partner grocers. Ends Nov 1.
Shake a bag of mixed candy and the chunky bars end up on top, every single time, even though they are heavier. Physicists call it the Brazil nut effect, after the big nuts that always surface in a can of mixed nuts. Rosato, Strandburg, Prinz and Swendsen first simulated it in 1987, and it still has no single textbook answer: three mechanisms work together.
At every shake the pile lifts off the bottom for a split second. A gap opens under the big bar, and a gummy or a peppermint is small enough to drop into it. A gap under a small candy is almost never big enough for the bar. One way traffic: small down, big up, a few millimetres per shake.
Friction with the bag walls drags candy down along the sides, so the middle flows up. Knight, Jaeger and Nagel filmed these rolls in 1993. The rising stream carries big bars to the top; the sinking stream near the walls is a narrow crack only small candy can follow.
Nothing happens while the bag accelerates less than gravity: the candy rides along as one solid block. Above Γ = 1 the pile leaves the floor, falls back, and rearranges. Try it in the bag above: at 0.8 g every candy stays put.
Every tag shows the price per 100 g, so a 40 pack and a 2 kg bulk bag finally speak the same language. Prices in Canadian dollars, taxes extra.
40 fun size bars × 17 g
70 snack packs × 18 g
2 kg bulk bag, about 400 drops
180 lollipops × 6 g
1 kg, about 150 wrapped toffees
120 foil coins × 5.5 g
1.2 kg resealable bag
30 fun size bars × 21 g
900 g, about 110 twists
The number that matters on October 31 is not the bag price: it is what each knock at the door costs you. Type what is on the shelf tag.
Fun size bars feel generous at the door, but the wrapper weighs on the price. We weighed 1,840 treats from 31 bags to build this table.
| Format | Typical bag | Per 100 g | Per treat | Cost scale | Best for |
|---|---|---|---|---|---|
| Bulk hard candy, unwrapped by the kilo | 2 kg · $13.49 | $0.67 | $0.04 | Cheapest | |
| Mixed lollipops, individually wrapped | 180 pc · $12.99 | $0.98 | $0.07 | Big crowds | |
| Gummy packs, 18 g each | 70 pc · $11.97 | $0.95 | $0.17 | Best value | |
| Fun size chocolate bars, 17 g | 40 pc · $8.97 | $1.32 | $0.22 | Crowd favourite | |
| Mini peanut cups, 14 g | 45 pc · $10.49 | $1.66 | $0.23 | Grown-up doors | |
| Full size bars, 52 g | 24 pc · $27.99 | $2.24 | $1.17 | Legend status |
Founder · flyer scanner
Former grocery category buyer. Reads 412 weekly flyers before breakfast and knows which ones bluff.
Granular physics · the bag
PhD in granular flows from a Québec engineering school. Built the shake simulation with 447 bodies and 1,200 steps a second.
Price data · unit pricing
Weighs every format we list, wrapper included, and catches shrinkflation the week it ships.
Allergy desk · labels
Checks every nut free and gluten free claim against the actual label, not the marketing.
“We get 160 visitors on our street. The price per treat calculator told me to skip the fun size bars and mix gummies with lollipops. Nobody complained, and I spent half.”
“My kids shake the bag every morning in October to see what comes up. It became our breakfast game, and the deal it shows is usually the one I buy.”
“I run a school fair. The November 1 tracker found 4 kg of leftover chocolate at 70 % off. One star off only because I want the alerts even earlier.”
Every Friday in October: the 5 deals that rose to the top of the bag, the clearance calendar, and one coupon code you will not find in the paper flyers.
SPOOKY12