Pecan halves

One US cup of pecan halves weighs 99 grams. Going the other way, 100 grams is about 1.01 cups.

Also called whole pecans, pecan kernels, pecans (whole), raw pecan halves.

Two sources agree within tolerance. USDA FDC 170182 (Nuts, pecans, SR Legacy) publishes 1 cup halves at 99 g, implying a density of 0.4185 g/mL. King Arthur's Ingredient Weight Chart lists 'Pecans (whole)' at 105 g per cup, implying 0.4438 g/mL. The gap between them is 6.06%, inside the 10% milled tolerance for whole and chopped nuts, so this entry publishes USDA's figure of 99 g per cup and names both sources. Neither source names a specific filling method.

The contrast with walnut halves is instructive. This site publishes walnut halves as a range of 99 to 128 g per cup because USDA and King Arthur disagree by 29.3% on that ingredient. Pecans do not show the same disagreement despite being a physically similar product. The reason is shape: pecan halves have a consistent crescent geometry that packs into cups with more predictable air gaps, while walnut halves are irregular and their fill depends heavily on orientation. Two pecan crescents interlock in roughly the same way regardless of who fills the cup; two walnut halves do not. This is why pecan halves qualify for a published figure and walnut halves do not.

The comparison with chopped pecans, published here at 109 g per cup from the same USDA record, shows only a 10 g difference against the whole-halves figure. Chopping pecans has less effect on density than chopping walnuts because the pieces come apart along the same crescent axes and settle into similar arrangements. Chopped pecans are therefore only marginally denser than whole halves, whereas chopped walnuts are meaningfully denser than whole walnut halves.

Pecan meal, a fine grind used as a partial flour substitute in shortbread and tart crusts, is a distinct product. King Arthur publishes pecan meal at 80 g per cup, roughly 20% less dense than the halves figure, which is expected: finer particles trap more air and pack less predictably than whole crescents. Pecan meal will be added as a separate entry when USDA data confirms the figure.

Pecans are placed in the milled category alongside other whole and chopped nuts. The category rule assigns whole and chopped nuts to milled because they pack by scoop with air gaps, in the same way whole seeds and grains do. The 10% category tolerance applies here, and the 6.06% observed gap between sources is well inside it.

No standards body publishes a bulk density for pecans or other tree nuts. Codex Alimentarius standards for tree nuts cover moisture content, defect tolerances and shell fragment limits but not physical density. Two sources agree within tolerance, both from authoritative independent publishers, so this entry is held at medium confidence. A third independent source (a professional culinary reference or a producer's laboratory measurement) matching within tolerance would move it to high confidence.