Crème fraîche

One US cup of crème fraîche weighs 240 grams (8.5 ounces). Going the other way, 100 grams is about 0.42 cups.

TL;DR: 240 g/cup (1.014 g/mL). Multi-source convergence across USDA branded data, Vermont Creamery, Trader Joe's, and French cooking references. King Arthur lists 248 g/cup, roughly 3% higher — almost certainly a fractional-ounce rounding artifact rather than a real disagreement.

Crème fraîche is thick cultured cream, French in origin but now widely produced domestically, made by fermenting heavy cream with mesophilic bacterial cultures until it thickens without souring as sharply as American sour cream. French-style crème fraîche typically hits 30-40% milkfat, higher than sour cream's ~20% and roughly matching lightly whipped heavy cream. The result is spoonable but dense enough to hold a dollop, tangy but nutty rather than sharp, and — because the cultures dominate the tang and the fat content buffers acidity — stable enough not to break when heated, which is the culinary property that makes it prized over sour cream in warm sauces and pan reductions.

Density data converges tightly. USDA FoodData Central's branded entry for crème fraîche (UPC 071448300595) gives 237 g per US cup, or 1.00 g/mL. Vermont Creamery, the dominant US producer of French-style crème fraîche, publishes a serving of 1 oz = 28 g and per-tablespoon data of 15 g, extrapolating to 240 g/cup. Trader Joe's Crème Fraîche lists 2 tbsp = 30 g on the label, also 240 g/cup. French cooking references and density-based converters both settle at 240. Physics predicts 239 g/cup for 30% milkfat and 238 g/cup for 40% milkfat cultured cream, so 240 fits the retail product profile squarely. King Arthur's Ingredient Weight Chart lists crème fraîche at 1/2 cup = 4 1/3 oz = 124 g, extrapolating to 248 g/cup — 3.3% higher than the producer consensus. That gap is almost certainly a rounding artifact: converting the producer figure of 240 g/cup back to ounces gives 4.23 oz per half-cup, which KA appears to have rounded up to the neat fraction 4 1/3.

Within the semi-solid dairy family, crème fraîche sits between heavier and lighter neighbors on the scale. Sour cream (227 g/cup in the King Arthur convention) is thinner and tangier at 18-20% milkfat, with more lactic acid and a tendency to break in hot pans. Mascarpone (227 g/cup, high confidence) is at the other side of the flavor axis: 44% milkfat, mild rather than tart, denser-feeling in the mouth despite the similar cup weight. Cream cheese (227 g/cup) and Greek yogurt (227 g/cup) both land near the same weight but behave differently in a recipe — cream cheese is emulsified and firmer, Greek yogurt sharper and higher in protein.

For the practical baker, crème fraîche can substitute for heavy cream 1:1 in cold or gently warmed applications with a tangier finish, for sour cream 1:1 in dips and dressings without the risk of splitting when the mixture eventually meets heat, and for mascarpone 1:1 in savory sauces though not in tiramisu-style desserts where mascarpone's fat content and sweetness carry the texture. Note that French-style crème fraîche (Vermont Creamery, Trader Joe's, Alouette) runs at 30-40% milkfat, while some domestic imitators labeled simply "cultured cream" or "cultured sour cream" run lower at 20-30% and behave more like sour cream on the pan; when heat stability matters, check the milkfat percentage on the label rather than trusting the product name.