You’ve seen it at every baby shower, wedding, and office party since the dawn of time. A glass jar, usually a Mason jar or some vintage apothecary vessel, sits on a table stuffed to the brim with silver and gold foils. There’s a stack of tiny slips of paper and a pen. Most people just glance at the container, shrug, and scribble down a random number like 150 or 400. They’re usually wrong. By a lot. Honestly, winning a guess how many kisses in the jar contest isn't just about luck or having "good eyes." It’s actually a mix of geometry, packing fractions, and a little bit of psychological trickery.
If you want to actually win—or if you’re the one hosting and you don't want the game to be a total flop—you have to understand the space. It’s about volume.
The Geometry of the Hershey's Kiss
Hershey’s Kisses are an absolute nightmare for math nerds. They aren't cubes. They aren't spheres. They are what mathematicians might call a frustum-like shape with a tapered top, but in common parlance, they’re just little "flat-bottomed cones." Because of that weird little plume at the top and the flared base, they don't sit flush against each other. This creates "void space."
When you toss a handful of candy into a jar, they settle in what’s known as "random loose packing." Unlike marbles, which have a predictable packing fraction of about 60% to 64%, Kisses are jagged. They snag on each other. Researchers and hobbyist mathematicians who spend way too much time on this have found that the packing efficiency of a Hershey's Kiss is roughly 50% to 55%. That means half of what you see in that jar is actually just air.
Think about that for a second.
Most people look at a jar and see a solid mass of chocolate. You need to see the gaps. If you treat the jar as if it's 100% full of chocolate, your guess will be nearly double the actual count. You’ll look like an amateur.
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Calculating the Win Without a Calculator
So, how do you actually do the "napkin math" while standing in a buffet line? First, you need to estimate the volume of the container. Most party jars are standard sizes.
- A Quart Mason Jar is about 946 milliliters (32 fluid ounces).
- A Pint Mason Jar is 473 milliliters (16 fluid ounces).
- A Large Gallon Jar is roughly 3,785 milliliters.
Now, here is the secret number: the average Hershey’s Kiss has a displacement volume of about 7 to 8 milliliters. But remember our "air" rule? Because they don't pack perfectly, each Kiss effectively "occupies" about 10 to 12 milliliters of space in a jar.
If you’re looking at a 32-ounce (quart) jar, don't just guess. Do the quick division. 946 divided by 12 is roughly 78 or 79. In reality, a quart jar usually holds between 75 and 100 Kisses depending on how much someone shook the jar to settle them. If the host packed them down tight, go higher. If they look loose and messy, go lower.
Why Your Brain Wants to Lie to You
The "Wisdom of the Crowds" is a real phenomenon first noted by Sir Francis Galton in 1906. He observed a contest at a livestock fair where people guessed the weight of an ox. While almost every individual guess was wrong, the average of all guesses was within 1% of the true weight.
In a guess how many kisses in the jar scenario, your brain suffers from "anchoring." If you see a previous guess written down on a slip of paper that says "500," your brain will naturally stay in that neighborhood, even if the jar clearly only holds 200. It’s a trap. Ignore the other slips.
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Also, consider the "visual fullness" illusion. We tend to overestimate the volume of tall, thin cylinders and underestimate the volume of short, wide ones. This is why bartenders love tall, skinny glasses—they look like they hold more than they do. If the contest is using a wide fishbowl, there are way more Kisses in there than you think. If it’s a tall cylinders, it's a "lie" container. Guess lower.
Hosting the Game: Keeping it Fair
If you're the one putting this together, don't be the person who loses count halfway through. It’s embarrassing. Count them into bags of 25 as you fill the jar. Write the final number down and hide it in your phone—not on a piece of paper that can be found in a kitchen drawer.
You should also decide on the "Price is Right" rules versus "Absolute Proximity." Generally, "closest without going over" is the most fun because it adds a layer of strategy. If you're using a massive jar, provide a "cheat sheet" or a sample small jar next to it with a known quantity (e.g., "This small jar has 20 Kisses"). It helps people calibrate their eyeballs and prevents 4,000-count guesses for a jar that holds 300.
Real World Examples and Discrepancies
I’ve seen people use the "layer method." You count how many Kisses are on the bottom layer—let's say it's 10. Then you count how many layers high the jar is—let's say 8. 10 times 8 is 80. Then you add a "buffer" of about 10% because the middle is usually denser than the edges.
But wait.
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What if they aren't standard Kisses? The Hugs (the striped ones) or the Almond Kisses have slightly different dimensions. Specifically, the Almond ones are bulkier. If the jar is a mix, the packing fraction drops even lower because the irregular shapes create even more air pockets. Your guess should be more conservative.
The Winning Strategy Step-by-Step
- Identify the Jar: Is it a 32oz Mason jar? A 64oz half-gallon? Identify the volume in milliliters if possible (Google the jar type if you can see a brand name on the bottom).
- Count the Base: Count how many candies are touching the glass at the very bottom.
- Count the Height: Count the vertical "rows" from bottom to top.
- The Multiplier: Multiply (Base x Height) x 0.75. Why 0.75? Because the jar tapers and the Kisses aren't squares. This factor accounts for the empty space and the rounded edges of the jar.
- Adjust for "The Plume": If the jar is filled into the neck (the skinny part at the top), add 5 to 10 more.
Final Actionable Insights
Winning this game isn't a superpower. It’s just refusing to be fooled by empty space. Next time you're at a baby shower, don't look at the chocolate—look at the air between the chocolate.
Your Winning Checklist:
- Check the bottom of the jar for a volume marking (e.g., "1 quart").
- Use the "12ml per Kiss" rule for standard 32oz jars—this usually lands you around 80.
- If the jar is a massive 1-gallon glass canister, your target number is likely between 320 and 350.
- Always guess an odd, specific number like 87 rather than 80. It suggests you have a "system," and in the event of a tie-breaker, specific numbers often win out over rounded ones.
Go ahead and take a long look at the jar. Count the layers. Do the math. And for heaven's sake, don't let the silver foil distract you from the volume of the glass.