
Show of hands, please: have you ever tried to take a recipe that goes by weight and tried to convert it into cups, or vice versa? Did that recipe work out for you or did it leave something to be desired?
If it was a success, then HOORAY for you! Gold star on the fridge by your name!
Most people aren’t so lucky. 😉
Totally ignoring the perpetual argument over whether “metric is better than imperial” when it comes to measurement (ahem IT IS FIGHT ME), there are two schools of thought when it comes to measuring out your ingredients as you gather your mise-en-place in the baking world.
One is measuring by VOLUME (cups, teaspoons, litres, etc.), and the other is measuring by WEIGHT (grams, pounds, ounces, etc.)
The Volume school of thought is absolutely everywhere in the non-professional (i.e. home-based) baking world; you can hardly pick up a North American cookbook or baking book that doesn’t have recipes scaled out in cups, teaspoons, and the like. Most cookbooks focused upon the home cook/baker will list their recipes like this, as common knowledge assumes that a high percentage of home cooks and bakers may not have a scale but will have dry and liquid measuring cups and spoons.
Simple, right?

Well, how to say this diplomatically: measuring by volume is simple, but inaccurate. Imagine if you will, a pound of feathers versus a pound of rocks. While the two items may weigh exactly the same, they would be far different in the space they occupy, i.e. volume.
Let’s put this in baking terms: have you ever made the same cake recipe several times in a row and there are times it will come out perfectly, but then there’s that one time (usually when it’s most important) that it’s completely borked and you don’t know why?
I get it; this method is far more familiar and much easier than laboriously having to weigh every ingredient out by the gram or milliliter, pound or ounce. However, it’s accepted in the professional baking world that weighing by volume is quite risky if you’re looking for the exact same results every time you bake something; think of how many different ways there are to measure a cup of flour:

Do you scoop directly from the bag? Do you scoop into your measuring container using another smaller scoop? Do you sift your flour before or after you measure it? Do you level off the top of your measuring cup with a flat-bladed knife, or allow a bit of a peak on top?
All of these actions will cause a small difference in the actual amount of product you’re using. Not so much of an issue in cooking, and probably not a huge deal if you’re making only one loaf of bread or one cake, but you can imagine if you 5x that recipe (think Christmas cookies or multiple banana loaves), and now that small change, that “little extra” or “little less”, has just been magnified by a factor of 5. This is a major reason why a tried-and-true baking recipe can all of a sudden turn out dry or soggy, peaked or sunken.

Imagine pro bakers scaling up these recipes to make 100-150 loaves or 500+ cookies at a time….now try explaining you used volume instead of weight measurements to the Kitchen Manager (aka God/The BigBoss/YES CHEF!) and NOT getting fired.
This is why professional or skilled home bakers who want the highest chance of having their recipes turn out perfectly every time will use the weight method. 250g of granulated sugar will always be 250g of granulated sugar (note: see below where I totally contradict myself share the exception to this rule). And hell, ingredients are too expensive to be wasting on so rookie a mistake as bad measuring.

So let’s say I’ve convinced you that weight is the way to go…but then you look at your dozens of cookbooks using volume measurement, and you think, “Oh hell no.” Don’t fret, all is not lost; you can convert any volume-measured recipe into a weight-measured recipe and vice versa, but you didn’t hear that from me!
But here’s the tricky part: let’s say you have a professional baking recipe that calls for 250 grams of brown sugar. Well, your handy-dandy google-converter tells you that 250g is about a cup’s worth. But…like I mentioned in the example above, what if your recipe called for 250g of feathers? You’ll have much more than a cup of feathers. And I’m pretty sure that you may not have a baking recipe in your hands if you’re cooking with feathers…but that’s neither here nor there.
This is the reason why converting volume to weight arbitrarily doesn’t work. Weight doesn’t always amount to volume. Packed brown sugar is heavier than white sugar. Sprinkles take up more volume than raisins even though you might have 200g of both. From the other perspective, a cup of whipped cream will not weigh the same as a cup of unwhipped heavy cream.
If you are going to use a conversion chart and you’re desperate, another option is this chart, which gives you the weight charts for common baking ingredients.

Another (somewhat obsessive but perfectly viable) option, if you are still not getting the results you want with your recipes and you think your measurements may be off, weigh everything in your pantry. Write your own measurements down in a little book and keep them handy when baking so you truly understand not only weight-to-volume conversion, but also that the brands you buy may be different than the standard. Think all flours are the same? Think again. Different varietals of wheat and different milling processes can have a significant impact on volume. Even one brand of boxed kosher salt weighs differently cup for cup than another.
If you’re once again feeling the “oh hell no” overcome you, then may I recommend a shortcut? I’d check out this site from King Arthur Flour which has done much of the work in pre-measuring the standard averages for a number of baking ingredients. Granted, KAF uses their own flour and products for many of these weight averages (duh), but it’s a start! In general, the KAF website is a fantastic resource for those kitchen enthusiasts who really want to understand the mechanics behind baking.

My last word on the subject: in the mainstream professional baking world, all recipes are written by weight. This is to ensure accuracy and consistency. That being said, I BEG OF YOU to go out and buy yourself a handy-dandy digital kitchen scale. You can usually get a digital scale that will weigh up to 5 lbs for about $20-25, and up to 12 lbs for $30-35. Anything more expensive than that is starting to get into “institutional-use” territory, and is usually unnecessary.
Ok, enough of this subject; I’m boring even myself. Just stick by these words, and you’ll be on your way to becoming an at-home-pro-baking-god(dess)! Enjoy!