Why weighing beats measuring cups (with the numbers)

Measuring cups measure space. Baking depends on amounts. For water, those are close to the same thing. For flour, sugar, salt and cocoa, they are not.

Here's what goes wrong with cups, with real numbers, and how a scale fixes it.

Problem 1: flour packs

King Arthur Baking says a cup of all-purpose flour, fluffed, spooned in and leveled, holds about 120 g. Scooped straight from a packed bag, the same cup can hold up to 160 g.

That's 33% more flour from the same cup. Over a recipe:

Recipe calls for	Spooned and leveled	Packed scoop (worst case)	Extra flour
1 cup	120 g	160 g	40 g
2 cups	240 g	320 g	80 g
3 cups	360 g	480 g	120 g

An extra 120 g of flour is the difference between a soft sandwich loaf and a brick. King Arthur's scale guide puts the real-world range a bit lower, warning you could use "up to 25% more flour" than the recipe developer intended. Either way, it's more than enough to ruin a cake.

A scale gives you 120 g every time. King Arthur notes that being within 5 g of the target generally won't affect the result. A basic digital scale reads in 1 g steps, so it easily stays inside that window.

Problem 2: salt brands differ wildly

Salt is where volume measures go most wrong. The crystals of different salts are shaped differently, so a spoonful of each weighs a very different amount. From the King Arthur chart:

Salt	1 tablespoon	1 teaspoon
Table salt	18 g	6 g
Morton kosher salt	16 g	5.33 g
Diamond Crystal kosher salt	8 g	2.67 g

A recipe tested with Diamond Crystal and made with table salt gets more than twice the salt. Made the other way round, it gets less than half.

By weight, the problem disappears. If a bread recipe calls for 10 g of salt:

• Table salt: 10 ÷ 6 = 1.67 tsp.
• Morton kosher: 10 ÷ 5.33 = 1.88 tsp.
• Diamond Crystal: 10 ÷ 2.67 = 3.75 tsp.

Same 10 g. Three different spoon counts.

Problem 3: cups themselves aren't exact

The US cup is defined in NIST Handbook 44 as 8 fluid ounces, about 237 mL. NIST's metric kitchen page rounds that to 240 mL for everyday cooking and labels all its kitchen equivalents "approximate." A tablespoon is about 15 mL and a teaspoon about 5 mL.

Real measuring cups and spoons are made to those sizes with some tolerance, and King Arthur's scale guide warns that the lines on many liquid measuring cups aren't placed accurately. A scale doesn't care what shape the container is.

Problem 4: sticky and awkward ingredients

Honey, molasses and peanut butter cling to cups and spoons. You never get it all out, and you get a sink full of sticky tools. On a scale, you set the bowl down, press tare to zero it and pour straight in. Then tare again and add the next ingredient. One bowl, nothing to scrape.

What weighing doesn't fix

• Recipes written in cups. If a recipe was developed by scooping, its author may have used more flour than the chart says. The weight chart tells you what the recipe should mean, not how the author measured.
• Very small amounts. King Arthur notes standard kitchen scales can be unreliable under about 1 oz (28 g). For a teaspoon of yeast or baking soda, a measuring spoon is fine, or use a small precision scale.
• Your oven. Exact ingredients won't fix an oven that runs hot. See our oven temperature chart.

How to start, in five steps

1. Buy a digital scale that reads in grams with 1 g steps and has a tare button. A flat platform is easier to read under a big bowl.
2. Check it. King Arthur suggests a US nickel weighs 5 g, so six nickels should read close to 30 g.
3. Convert your favorite recipe once. Use the cups to grams converter for each ingredient and write the grams on the recipe card.
4. Bake it by weight. Put the mixing bowl on the scale, tare, add the first ingredient. Tare, add the next.
5. Keep spoons for the small stuff. Leaveners, spices and extracts under a tablespoon are fine by volume.

A worked example: chocolate chip cookies

A typical cookie recipe in cups, converted with the King Arthur chart:

Ingredient	Cups	Grams
All-purpose flour	2 1/4 cups	270 g
Butter	1 cup (2 sticks)	226 g
Granulated sugar	3/4 cup	149 g
Brown sugar, packed	3/4 cup	160 g
Chocolate chips	2 cups	340 g

Scooped and packed, that flour could weigh up to 2.25 × 160 = 360 g. That's 90 g more than intended, and it shows up as thick, dry, cakey cookies. Weighed, it's 270 g every batch.

For the flour numbers behind all this, see how many grams in a cup of flour. For butter, see butter conversions.