Ketchup — Cups to Grams

Ketchup in Sauces and Glazes: Key Ratios

Ketchup functions as a pre-seasoned tomato base in many sauce applications. It contributes tomato flavor, sweetness (up to 28g sugar per 100g), acidity (vinegar), and thickening (tomato solids + pectin). Understanding the proportions in common applications helps you scale and adjust recipes confidently.

The meatloaf glaze deserves particular attention. The two-coat technique — first coat 30 minutes before done, second coat 10 minutes before done — caramelizes the sugar in the ketchup (the caramelization point for fructose and glucose is 110–120°C). The first coat creates a tacky surface; the second coat builds on the caramelized layer. A single thick coat of ketchup applied at the start produces a different, less caramelized result.

Ketchup vs Tomato Paste: Density Comparison

Ketchup (255g/cup) is slightly less dense than tomato paste (262g/cup) despite containing more added sugar. This unintuitive result is explained by the different solids concentrations: tomato paste is 30–40% tomato solids, while ketchup is approximately 25–27% tomato solids. Ketchup also contains more water relative to its solids due to its sauce consistency, whereas tomato paste is a concentrated reduction.

They are not interchangeable as flavor-for-flavor substitutes. Tomato paste delivers pure, concentrated, slightly caramelized tomato flavor with no added sweetness or acidity. Ketchup delivers a complex sweet-sour-savory flavor from tomato, sugar, and vinegar. If a recipe calls for tomato paste and you only have ketchup, use 3–4 tablespoons of ketchup per tablespoon of tomato paste and reduce or eliminate added sugar and vinegar in the recipe. If substituting ketchup for tomato paste in a pasta sauce, the result will be noticeably sweeter and more vinegary.

The Food Science of Ketchup's Density

Ketchup is denser than water (255g vs 240g per cup) because of dissolved and suspended solids. Sucrose in ketchup dissolves to form a sugar solution — each gram of dissolved sugar increases the density by approximately 0.4g/100ml above pure water. With 28g sugar per 100g ketchup, the sugar contribution alone accounts for much of the density excess over water.

Ketchup is classified as a non-Newtonian pseudoplastic fluid. At rest, tomato pectin and cellulose fiber form a weak gel network that gives ketchup its characteristic thick-but-flowable consistency. Under shear stress (squeezing, shaking, stirring), this network breaks down and viscosity decreases — the ketchup flows. Remove the stress and the network reforms. This "thixotropic" behavior explains the famous stuck-ketchup-bottle problem: the ketchup at the bottle neck has reformed its gel structure from sitting undisturbed. The solution is not to shake or tap the bottom, but to tap the side of the bottle neck where the ketchup-air interface exists, introducing shear stress at exactly the right point.

Common Questions About Ketchup

• How many grams in a tablespoon of ketchup?

  1 tablespoon of ketchup weighs 17 grams. 1 teaspoon = 5.7 grams. ¼ cup = 64 grams. ½ cup = 128 grams. 1 cup = 255 grams. A fast food single-serve foil packet = approximately 9–10 grams (about ½ tablespoon).

• How much ketchup is in a 20 oz bottle?

  A 20 oz (567g) bottle contains approximately 2.2 cups (560g) of ketchup. A 32 oz (907g) bottle yields approximately 3.6 cups. For BBQ sauce recipes calling for "1 cup of ketchup," you'll use just under half of a 20 oz bottle.

• Is ketchup the same density as tomato sauce?

  No. Ketchup (255g/cup) is denser than canned tomato sauce (245g/cup) due to its higher sugar content and more concentrated tomato solids. Ketchup also contains vinegar and spices absent in plain tomato sauce. They are not equivalent flavor substitutes — ketchup is sweeter and more acidic, tomato sauce is milder and more neutral.

• Why does ketchup get stuck in the bottle?

  Ketchup is a non-Newtonian pseudoplastic fluid — it forms a weak gel structure when undisturbed. The ketchup at the bottle's opening reforms its gel after sitting still, effectively blocking flow. To break the gel: tap the side of the bottle neck firmly, apply a slapping motion to the bottom while tilted, or insert a clean knife to mechanically disrupt the gel structure at the opening. Squeezing bottles avoid this problem by keeping the ketchup moving.