Mayonnaise

One US cup of mayonnaise weighs between 208 and 226 grams, depending on how the cup is filled and which source measured it. That range is the answer; a single number would not be. Every figure behind it is below, with the method each source used.

Also called mayo, real mayonnaise.

Mayonnaise weighs 208-226 g/cup depending on brand. King Arthur lists 226 g/cup on their ingredient weight chart, USDA's reference sits at about 220 g/cup, and the two dominant national brands (Hellmann's and Kraft) label at 208 g/cup. Duke's, the Southern regional dominant brand, sits at 224 g/cup. No single value is defensibly correct across all commercial mayonnaise.

Mayonnaise is FDA-defined as an emulsion containing at least 65% vegetable oil, plus egg yolks or whole eggs, vinegar or lemon juice, and typically water and salt. That composition puts it firmly in the fat category despite its spreadable emulsion form — physically it packs and scoops like other fat-dominant spreads (peanut butter, almond butter, tahini), not like liquids. The oil-in-water emulsion structure gives mayo a density close to but slightly below its oil component, since the small amount of water and eggs raises the composite density above pure oil (0.92 g/mL) toward roughly 0.93-0.96 g/mL depending on formulation.

King Arthur has mayonnaise on their weight chart at 226 g/cup, and unlike many entries where this catalog corrects KA, no correction is warranted here. Their figure aligns with the USDA reference (220 g/cup) and the Duke's label (224 g/cup). The chart entry is old — mayonnaise has been on standard baking charts for decades — and it likely reflects a mid-1990s reference formulation before the light-mayo era shifted the market toward lower-fat, higher-water products.

The density spread across current brands reflects real formulation differences. Hellmann's (also sold as Best Foods) and Kraft both label at 13 g per tablespoon, giving 208 g/cup, and together represent a majority of US retail mayonnaise sales. Duke's runs slightly heavier at 14 g per tablespoon (224 g/cup), consistent with their marketing emphasis on higher egg-yolk content and no added sugar. Historical USDA references from earlier decades list mayo at 15 g per tablespoon (240 g/cup), reflecting the higher-fat formulations typical before commercial reformulation trends nudged product lines toward lower oil content.

One technical note on the Hellmann's/Kraft label figure: 13g in a 14.79 mL tablespoon equals a density of 0.879 g/mL, which is suspiciously close to pure vegetable oil and below the physical density of a typical 77% fat oil-in-water emulsion. FDA nutrition label rounding rules for values between 5g and 49g round to the nearest 1g, so a true weight of 13.5g would round down to 13g on the label. The 208 g/cup figure derived from the label may therefore slightly understate the actual density of the product. Either way, that is what the label states, and it is what a consumer reading the package would calculate.

Light and reduced-fat mayonnaise are distinct products and not covered by this entry. Light mayo has substantially more water (often 40-50% water versus 15-20% for regular), which changes the density even though the volume-per-tablespoon label figure often stays similar (15g for Hellmann's Light versus 13g for regular).

Practical baker guidance: for chocolate mayonnaise cake and other recipes where mayo replaces some fat and eggs, 220 g/cup is a reasonable default when the recipe does not specify a brand. For volume-only recipes, the difference between brands (208 to 226 g/cup) is roughly 9%, which affects moist quick-bread textures noticeably but not catastrophically. Weighing to the recipe developer's stated gram figure is the most reliable path when precision matters.