What size jar for a pound of jam

Why we will not give you a conversion

A fluid ounce is a volume and a pound is a weight, and jam is denser than water, so there is no fixed conversion between the number on the jar and the number you declare. Any table claiming otherwise is averaging across products that differ, and the error lands on your label where it is expensive.

Because it would be wrong for your product. Density moves with the soluble solids and with the fruit, so a figure that works for a 66-Brix seedless raspberry jam does not work for a looser plum one. What is true for everybody is that a jar holding 8 fluid ounces holds more than 8 ounces of jam by weight, and that is the direction first orders get wrong.

Settling it in ten minutes

The answer is available in your own kitchen in less time than it takes to search for it, and it is correct for your product rather than for an average of somebody else's.

1. Weigh the empty jar and write it down.
2. Fill it to the headspace you actually use, a quarter inch.
3. Weigh it again and subtract.
4. That number is the net weight you can declare in that jar. Order against it, not against the fluid-ounce figure on the box.

The sizes this product sells in

Jam sells in a narrow band of sizes and the reasons are commercial rather than technical. Knowing the band saves specifying something that is correct and unsellable. A size that is technically fine and unfamiliar on a shelf is a size you will be explaining at every market, and explaining a jar is time not spent selling one.

8 oz Clear Glass Tapered Jam Jar

8 oz · 70-450G · Glass · case of 108

The tapered jam jar in the retail default size. The taper is what lets a spoon reach the bottom corners.

$1.13

each

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8 oz Clear Glass Mason And Paragon Jar

8 oz · 58-400 · Glass · case of 96

The same size as a mason jar, which a buyer reads as homemade. Cheaper per unit and a narrower neck.

$0.91

each

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4 oz Clear Glass Straight Sided Jar

4 oz · 58-400 · Glass · case of 84

The gift and sampler size. Sold in threes and fours rather than singly.

$0.78

each

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The mistake

Buying one size for all three channels. A market stall, a farm shop and a bakery want different sizes, and a case of the wrong one is a case you own for a year.

References