At last! A compendium of US-to-metric conversions to use when baking. This might be kinda useful for you international folk wanting to try my recipes, huh?
I'll be honest—I wish we used metric here in the US. Everything would be more streamlined, not to mention kitchen scales are so much fun to use. Anyhow, the trouble with the US measuring system of using cups to measure dry ingredients is that it's a system of volume and not mass or weight. This means that you can't simply say "1 cup of (insert dry ingredient) equals x grams" because each ingredient you're dealing with weighs differently. One cup of flour weighs less than one cup of sugar. The workaround, then, is to consider each dry ingredient separately when converting US cups to grams. Which is what I've done below.
I've also included conversions for liquids and temperatures below—those are much more straightforward in their conversions.
One more thing of note—I prepared this guide based on my own ingredients and methods for transferring ingredients when measuring (e.g., scooping versus pouring), so these conversions will work best with the recipes on my site. You'll see some slight variations on other sites. But feel free to use these conversions as a guide for other US recipes!
Important note: I measured all of these dry ingredients by first scooping them into a 1 cup measuring cup with a traditional teaspoon (of the silverware sort). Then I poured the contents of the measuring cup into a bowl on a zeroed kitchen scale. This means that when measuring using a kitchen scale, you'll want to scoop your dry ingredients into the bowl on your scale instead of pouring them.
Also, I did not sift any dry ingredients in this process, nor do I ever sift before measuring, so whenever I say to "sift" in a recipe, I mean for you to do it after measuring. (In other words, no measuring flour that you've just sifted here.)
plain (all-purpose) flour
1 cup equals 126 g (4.5 oz)
1 cup equals 120 g (4.2 oz)
1 cup equals 98 g (3.5 oz)
1 cup equals 126 g (4.5 oz) — odd, I know, but you use it in this pretzel cake recipe
I've given sugars their own section since I don't generally consider them a dry ingredient in my recipes. I kinda label sugar a "wet" ingredient since I combine it with the butter and eggs first and not with the flour, baking powder, and salt.
Oh, and note: I measured each sugar a little differently. I poured the regular sugar into the 1 cup measuring cup and leveled it; I scooped powdered sugar into the measuring cup and then leveled it; and I packed the brown sugar into the measuring cup. I weighed each on a zeroed scale after leveling.
1 cup equals 221 g (7.8 oz)
1 cup equals 111 g (3.9 oz)
1 cup equals 215 g (7.6 oz)
1/2 cup (1 stick)
113.4 g (4 oz)
This is easy since you're dealing with volume in both US and metric measurements. The conversion, therefore, is direct for any liquid.
Teaspoons and Tablespoons
Did you know that a "teaspoon" in the US is a little smaller than a "teaspoon" in the UK and Europe? This means that you should go a little scant when using Imperial teaspoons to measure my US teaspoon amounts. (The same goes for tablespoons, by the way.) Keep in mind that we are dealing with smaller quantities here, which is why I haven't made a differentiation between dry ingredients and liquids.
Australia—you define a tablespoon as 4 teaspoons, whereas the US and Europe define a tablespoon as 3 teaspoons. Moreover, your teaspoon is exactly 5 mL, which is about equal in size to a US teaspoon. In turn, your tablespoon is exactly 20 mL.
1 US tsp equals 0.83 Imperial (UK) tsp
1 US tsp equals 4.9 mL
1 US tsp ~ 1 Australian tsp
1 US TB equals 2.5 Imperial (UK) TB
1 US TB equals 14.8 mL
1 US TB ~ 3/4 Australian TB
Temperature, Fahrenheit to Celsius
Another straightforward conversion. Granted, these temperatures are a little approximate since ovens don't let you get very specific. Treat these as suggested Celsius temperatures.
150°C or gas mark 2
165°C or gas mark 3
180°C or gas mark 4
190°C or gas mark 5
200°C or gas mark 6
220°C or gas mark 7
230°C or gas mark 8
Thank you, Wikipedia.