Baking Powder ↔ Baking Soda: the Substitution
Out of baking powder — or out of baking soda? They are not interchangeable 1:1, but each can stand in for the other. Per teaspoon of baking powder: ¼ tsp baking soda + ½ tsp cream of tartar (King Arthur, America's Test Kitchen, Arm & Hammer and McCormick all publish this rule). Per teaspoon of baking soda: 3 tsp (1 tbsp) of baking powder. Enter what the recipe calls for:
Why the lopsided ratios? A teaspoon of baking powder contains only about ¼ teaspoon of actual baking soda — the rest is dry acid and a starch buffer (Arm & Hammer). So replacing soda takes 3× the volume of powder, while replacing powder takes just a quarter of the soda plus the acid the powder would have brought along. One honest dissent: Sally's Baking Addiction declines to publish any swap and says just don't; the ratios here are from the primary sources that do publish one, caveats attached.
Baking powder → baking soda + cream of tartar
The recipe calls for baking powder and the tin is empty. Per teaspoon of powder, use ¼ tsp baking soda + ½ tsp cream of tartar:
| Baking powder called for | Baking soda | Cream of tartar |
|---|---|---|
| ½ tsp | ⅛ tsp | ¼ tsp |
| 1 tsp | ¼ tsp | ½ tsp |
| 1½ tsp | ⅜ tsp | ¾ tsp |
| 2 tsp | ½ tsp | 1 tsp |
| 1 tbsp (3 tsp) | ¾ tsp | 1 ½ tsp |
| 4 tsp | 1 tsp | 2 tsp |
Two fine points. The mix is single-acting — it starts fizzing the moment it gets wet and has no oven-triggered second rise — so get the batter into the oven right away (America's Test Kitchen's instruction). And you may meet ⅝ tsp of cream of tartar in older charts: that's the USDA-lineage figure Utah State and Texas A&M extensions still carry, slightly closer to the exact chemistry; the ½ tsp everyone else prints is the rounded kitchen version. Both work.
No cream of tartar? Every acid that works
All of these pair with the same ¼ tsp of baking soda to replace 1 tsp of baking powder:
| Acid | Amount (per ¼ tsp soda) | Notes |
|---|---|---|
| Cream of tartar | ½ tsp | The standard: King Arthur, ATK, Arm & Hammer, McCormick (older USDA figure: ⅝ tsp) |
| Lemon juice or white vinegar | ½–1 tsp | Sources genuinely disagree: King Arthur ½ tsp; Arm & Hammer & McCormick 1 tsp; Utah State ½ tbsp stirred into milk to make ½ cup |
| Buttermilk, yogurt or sour cream | ½ cup | ATK & Utah State. Count it as part of the recipe's liquid, not an addition |
| Molasses | ¼–½ cup | Utah State — acidic enough to fire the soda; reduce other sweetener to match |
Baking soda → baking powder: use 3×
The recipe calls for baking soda and you only have powder — use three times as much. The 3× rule is unanimous across King Arthur, Bob's Red Mill, Arm & Hammer and McCormick (no primary source says 4×; that garble comes from misreading "soda is 3–4× stronger" as a dosing instruction):
| Baking soda called for | Baking powder instead |
|---|---|
| ¼ tsp | ¾ tsp |
| ½ tsp | 1 ½ tsp |
| ¾ tsp | 2 ¼ tsp |
| 1 tsp | 1 tbsp |
| 1½ tsp | 1 tbsp + 1 ½ tsp |
| 2 tsp | 2 tbsp |
Caveats from the sources themselves: King Arthur warns a slightly bitter, off-putting taste can result from that much powder; Bob's Red Mill suggests swapping acidic liquids (buttermilk) for non-acidic ones (milk), since the powder brings its own acid. And a fun catch — McCormick's own chart prints 2½ tsp in its ¾-tsp row, where 3× is 2¼ tsp; the rest of their table follows the rule. Charts get copied; arithmetic doesn't lie.
Homemade baking powder
Making powder rather than substituting per-teaspoon: mix 1 part baking soda with 2 parts cream of tartar — Bob's Red Mill's ratio; King Arthur's per-teaspoon version adds ¼ tsp of cornstarch to every ¼ + ½ tsp, which absorbs moisture so a stored batch doesn't fire in the jar. It behaves like the substitution above: single-acting, so bake promptly — commercial double-acting powder rises once at mixing and again in the oven's heat, and the homemade blend only does the first.
What's actually in the tin
Baking soda is pure sodium bicarbonate. Baking powder is soda plus one or two dry acids plus a starch — and here's a detail most charts miss: America's best-selling powder (Clabber Girl) lists cornstarch, sodium bicarbonate, sodium aluminum sulfate and monocalcium phosphate — no cream of tartar at all. The tartar version is the homemade and premium recipe; "aluminum-free" brands such as Rumford and Bob's Red Mill lean on monocalcium phosphate instead. Double-acting (nearly all US retail powder) means two rises: the first when the powder dissolves into the batter, the second when the batter heats in the oven — which is why store-bought batters can wait and homemade-powder batters can't.
How much per cup of flour?
Building or rescuing a recipe rather than converting one: the rules of thumb are ¼ tsp of baking soda per cup of flour (Arm & Hammer) or 1 to 1¼ tsp of baking powder per cup of flour (food scientist Shirley Corriher's rule) — the same 1:4 relationship as the substitution ratio, which is a nice sanity check. More leavener than that doesn't mean more lift: excess soda survives the bake unreacted and tastes soapy.
By weight: the sources disagree
Weighing leaveners is honestly messy, so we show the spread rather than pretending there isn't one: King Arthur's chart weighs a teaspoon of baking powder at 4 g and baking soda at 6 g; USDA data puts both at about 4.6 g; and the Arm & Hammer and Clabber Girl nutrition labels both work out to 4.8 g per teaspoon (⅛ tsp = 0.6 g). The differences come down to how hard the spoon is packed — and at these quantities they're under a gram, so this is the one place on this site we'll tell you to skip the scale and use the spoon.
Is it still good?
Leaveners fade rather than spoil, and each has its own test. Baking soda: stir ½ tsp into a few tablespoons of vinegar — it should fizz hard instantly. Baking powder: stir ½ tsp into a few tablespoons of hot water — water, not vinegar, because the powder carries its own acid and vinegar would make even dead powder fizz. Arm & Hammer's stated shelf life for soda is three years unopened; once open, the working consensus for either is 6–12 months. If a test barely bubbles, the substitution charts above won't save the bake — fresh leavener will.
Need a different conversion?
Swapping the sweetener too? The sugar to honey conversion leans on this exact chemistry — it adds ½ tsp of baking soda per cup of honey to neutralize the honey's acidity. The cake flour substitute is the reason self-rising flour isn't one (it's flour with about 1½ tsp of baking powder per cup already inside), and the butter to oil and cornstarch to flour pages run the same fixed-ratio-plus-caveats format. Swapping the other leavener? The yeast converter moves between active dry, instant and fresh. And teaspoons in a tablespoon spells out the spoon math used here (1 tbsp = 3 tsp).
Frequently asked questions
Can I use baking soda instead of baking powder?
Yes, if you add an acid. For every teaspoon of baking powder the recipe calls for, use 1/4 teaspoon of baking soda plus 1/2 teaspoon of cream of tartar — the substitution King Arthur, America's Test Kitchen, Arm & Hammer and McCormick all publish. No cream of tartar? Pair the 1/4 teaspoon of soda with 1/2 cup of buttermilk or yogurt, or with lemon juice or vinegar. Plain baking soda alone won't work: without an acid it makes no gas, and unreacted soda tastes soapy.
Can I use baking powder instead of baking soda?
Yes — use three times as much. Replace every teaspoon of baking soda with 3 teaspoons (1 tablespoon) of baking powder; King Arthur, Bob's Red Mill, Arm & Hammer and McCormick all publish the same 3x rule. King Arthur's caveat: that much baking powder can leave a slightly bitter note. Bob's Red Mill also suggests swapping the recipe's acidic liquid (buttermilk) for a non-acidic one (milk), since baking powder brings its own acid along.
How much baking soda equals 1 tablespoon of baking powder?
3/4 teaspoon of baking soda plus 1 1/2 teaspoons of cream of tartar. The rule is 1/4 teaspoon of soda plus 1/2 teaspoon of cream of tartar per teaspoon of baking powder, and a tablespoon is 3 teaspoons — so multiply everything by three.
Is it 1/2 teaspoon of cream of tartar or 5/8?
Both figures circulate, and both are legitimate. King Arthur, America's Test Kitchen, Arm & Hammer and McCormick all say 1/2 teaspoon of cream of tartar per 1/4 teaspoon of baking soda; Utah State and Texas A&M extension services carry the older USDA-lineage figure of 5/8 teaspoon, which is closer to the exact chemistry. The 1/2-teaspoon version is the rounded, kitchen-friendly one — either rises fine.
What if I don't have cream of tartar either?
Use a liquid acid with the same 1/4 teaspoon of baking soda per teaspoon of powder replaced. The sources genuinely disagree on the amount: King Arthur says 1/2 teaspoon of lemon juice or white vinegar, Arm & Hammer and McCormick say 1 teaspoon, and Utah State Extension stirs 1/2 tablespoon into milk to make 1/2 cup. Or skip the measuring spoon: 1/2 cup of buttermilk, yogurt or sour cream plus the 1/4 teaspoon of soda (America's Test Kitchen) — count that half cup as part of the recipe's liquid, not an addition.
How do I make homemade baking powder?
Mix 1 part baking soda with 2 parts cream of tartar — for one teaspoon's worth, 1/4 teaspoon of soda and 1/2 teaspoon of cream of tartar (Bob's Red Mill; King Arthur adds 1/4 teaspoon of cornstarch, which keeps a stored batch dry and free-flowing). One big caveat: homemade powder is single-acting — it fires as soon as it gets wet, with no second rise in the oven — so mix the batter and bake it right away, as America's Test Kitchen instructs.
Are baking soda and baking powder the same thing?
No. Baking soda is pure sodium bicarbonate and only makes gas when it meets an acid in the batter — buttermilk, yogurt, lemon, brown sugar, molasses. Baking powder is a complete kit: baking soda plus one or two dry acids plus a starch buffer (Arm & Hammer). That's why they can't swap 1:1 — a teaspoon of baking powder contains only about a quarter teaspoon of actual soda.
Why do I need 3 times as much baking powder to replace baking soda?
Because baking powder is mostly not baking soda — the dry acid and starch dilute it, so teaspoon for teaspoon it has only about a quarter of the leavening power (Arm & Hammer puts the equivalence at 1 teaspoon of powder = 1/4 teaspoon of soda). Watch a common garble: some sites say 'soda is 3-4x stronger' and turn that into a 4x substitution — every primary source that publishes a ratio (King Arthur, Bob's Red Mill, Arm & Hammer, McCormick) says 3x.
How much baking soda or baking powder per cup of flour?
The working rules of thumb: about 1/4 teaspoon of baking soda per cup of flour (Arm & Hammer), or 1 to 1 1/4 teaspoons of baking powder per cup (food scientist Shirley Corriher's rule) — the same one-to-four relationship as the substitution ratio. Treat them as ceilings as much as minimums: extra soda doesn't buy extra rise, it buys a soapy taste and a dark, coarse crumb.
How much does a teaspoon of baking powder or baking soda weigh?
The published figures honestly disagree. King Arthur's ingredient chart has baking powder at 4 g per teaspoon and baking soda at 6 g (listed as 1/2 tsp = 3 g); USDA data puts both at about 4.6 g per teaspoon; and Arm & Hammer's and Clabber Girl's own nutrition labels both work out to 4.8 g (1/8 tsp = 0.6 g). At leavener quantities the spread is well under a gram — measure with the spoon, not the scale.
How much baking soda does it take to neutralize 1 cup of buttermilk?
About 1/2 teaspoon. The number falls straight out of the substitution rule: 1/4 teaspoon of soda balances 1/2 cup of buttermilk (America's Test Kitchen, Utah State Extension), so a full cup takes 1/2 teaspoon. That's why recipes with both buttermilk and baking powder often add a pinch of soda — it's there to neutralize the dairy, not to leaven.
How do I test whether my baking soda or baking powder is still good?
Two different tests — don't mix them up. Baking soda: stir 1/2 teaspoon into a few tablespoons of vinegar; it should fizz hard immediately. Baking powder: stir 1/2 teaspoon into a few tablespoons of hot water — water, not vinegar, because powder brings its own acid; it should fizz visibly. Arm & Hammer gives unopened baking soda a three-year shelf life; once opened, the working consensus for either leavener is 6-12 months.