Hazelnuts

One US cup of hazelnuts weighs 135 grams. Going the other way, 100 grams is about 0.74 cups.

Also called whole hazelnuts, filberts, hazelnut kernels, raw hazelnuts.

Two sources agree within tolerance. USDA FoodData Central lists Nuts, hazelnuts or filberts (SR Legacy 12120) at 1 cup whole = 135 g, implying a density of 0.5706 g/mL. King Arthur's Ingredient Weight Chart lists 'Hazelnuts (whole)' at 1 cup = 142 g, implying 0.6003 g/mL. The gap between them is 5.19%, comfortably inside the 10% milled tolerance for whole and chopped nuts, so this entry publishes USDA's figure of 135 g per cup and names both sources. Neither source names a specific filling method.

Hazelnut kernels are roughly spherical, about 15 to 20 mm in diameter, and pack more efficiently than the crescent shapes of pecan or walnut halves. This is visible in the density figures across this site: pecan halves publish at 99 g per cup (0.4185 g/mL), walnut halves publish as a range of 99 to 128 g per cup because their sources disagree, pistachios publish at 123 g per cup (0.5199 g/mL), and hazelnuts sit higher still at 135 g per cup. Sphere packing has known geometric efficiency, and hazelnut kernels approximate that geometry more closely than the flatter or more irregular kernels of related tree nuts.

Chopped hazelnuts are a separate product with a different density and are not yet published on this site. USDA's own portion table for SR Legacy 12120 also lists 1 cup chopped at 115 g, roughly 15 percent lower than the whole-kernel figure. The reduction under chopping is unusual because most nut chopping increases apparent density by filling air gaps, as documented for pecans on this site, but hazelnut chopping produces angular fragments that can bridge and create voids that intact spheres do not. A chopped-hazelnut entry will be added when a second authoritative source (King Arthur does not list chopped or ground hazelnuts) becomes available to clear the two-source rule.

Product variants: raw versus dry-roasted hazelnuts differ by approximately 4% in moisture, which slightly increases apparent density after roasting but rarely crosses tolerance. Blanched hazelnuts, with the skin removed, show a very small mass reduction from the removed skin, well inside noise. Filbert is a common alternate name; the two words refer to the same genus (Corylus) and are used interchangeably in USDA nomenclature. In-shell hazelnuts roughly double the total weight because shell mass approaches kernel mass, and cup measurements of in-shell nuts are not useful for baking.

Hazelnuts are placed in the milled category alongside other whole and chopped nuts, whole seeds and whole grains. The category rule assigns these to milled because they pack by scoop with air gaps rather than filling by fluid displacement. The 10% category tolerance applies here, and the 5.19% observed gap between sources is well inside it.

No standards body publishes a bulk density for hazelnuts or other tree nuts. Codex Alimentarius has a standard covering hazelnut kernels for moisture content, defect tolerances, shell fragment limits and aflatoxin limits, but not physical density. Two independent authoritative sources agree within tolerance, so this entry is held at medium confidence. A third independent source, such as a professional culinary reference or a producer's laboratory measurement, matching within tolerance would move it to high confidence.