Just noticed this. Carbs are just hidden everywhere. I know the carbs are negligible for the amounts used in baking it’s the source of the carbs I’m more concerned about.
Luckily, I have baking soda + cream of tartar at home so will be making my own baking powder going forward.
Any recommendations for good and tested no carb baking powder will be appreciated. Or at least one whose carb source is not corn starch or rice flour.
Thanks.
Check the cream of tarter for carbs as well. 
Good lord. That shouldn’t even need additives of any sort.
The one I have is the one below
Doesn’t look like they’ve added anything to it, hopefully the label is being honest.
I just saw a post on another page about this after I posted that baking powder had corn starch in it and I didn’t want to consume those grains, small amount though it might be, and the reply was:
2 teaspoons of baking powder = 1 teaspoon of cream of tartar + 1/2 teaspoon of baking soda.
Check out this for a real eye opener!
Calorie Breakdown: 0% fat, 100% carbs, 0% prot.
Yep, that’s what I found as the way to make it as well. Might just keep using that combo for the long term unless I find a no carb baking powder.
So, pure carbs then 
I feel less bad using the cream of tartar combination because, at least the carb it contains is not sugar or starch. It contains like 600g of potassium per tspn though. I do wonder where the carbs come from though.
Interestingly, the brands I checked in the USDA Food Composition Database all claim 0 g of carbohydrate. They also all list cornstarch in their ingredients. Hmmm . . . .
A quick check of pure cornstarch shows it contains around 90% carbohydrate by weight, with negligible amounts of protein, fat, and fiber.
I suspect that it is added to the baking powder to keep it from clumping.
ETA: Cream of Tartar shows up in the database as 61.5% carbohydrate by weight, again with negligible amounts of anything else. Sodium bicarbonate (baking soda) contains nothing but sodium, according to the database.
Since in most recipes the quantity needed for leavening is so small, I suspect that the carbohydrate content of baking powder is probably not worth worrying about, especially in a recipe that makes several servings.
I think it’s one of those situations where they approximate the carbs to zero if the carb amount is less than a certain amount per serving.
I agree that it’s quite a small amount of carbs per serving though. I’ve just become a bit of a “carb detective” as I am trying to break a stall 
I don’t think there are any ‘added’ carbs. The compound is a carbohydrate. The chemical formula for ‘cream of tartar’, aka potassium hydrogen tartrate, is: C4H5O6K where the K = potassium and the CHO carbon, hydrogen and oxygen respectively. Technically, it’s an acid:
Potassium bitartate, also referred to as potassium acid tartrate or cream of tartar, is the potassium acid salt of l-( + )-tartaric acid. It is obtained as a byproduct of wine manufacture during the fermentation process. Approved by the FDA as a direct food substance, potassium bitartrate is used as an additive, stabilizer, pH control agent, antimicrobial agent, processing aid, or thickener in various food products [L2732]. Potassium bitartrate has a long history of medical use as a laxative administered as a rectal suppository and is an approved third-class OTC drug in Japan.
The reason corn starch is added is to help it not cake up, stay dry and keep reaction with ambient moisture minimal.
Baking soda with cream of tartar is known as single action baking powder, it reacts as soon as it gets moist.
Normally when you buy commercial baking powder it’s double action baking powder. It’s made with two different acids and soda The two acids react at different tempratures. There’s a second release of gas when it heated from the additional ingredient.
It’s a pretty small carb amount of you add a teaspoon for a recipe of a few servings.
You can use cream of tartar, vinegar or lemon juice with baking soda to get a single action powder substitute. If you decide to use your own mix they should not be mixed until your oven is completely ready. Do not mix a liquid acid with baking soda, you mix the lemon juice or vinegar into the liquid element of the batter or dough. You have to work fast when it’s mixed into a batter or biscuit dough. It’s tricky, and using tinned baking powder brings a higher success rate. 
