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Ingredient file // Vitamin or mineral

Calcium Sulfate

A plain mineral for calcium balance

Calcium sulfate is a mineral salt sold in feed grades such as ground gypsum. In dog food it adds calcium without adding phosphorus, which helps balance the recipe. Its name on the label cannot tell you whether the finished food is balanced.

Role in the food Supporting nutrient
What it is
A mineral salt containing calcium and sulfate, supplied in feed-grade form for formulated animal food.
Made from
Calcium sulfate mineral, such as ground gypsum
Main job
Calcium without phosphorus
Typical amount
Not published
Watch for
Extra calcium in a puppy's diet
Not the same as
Construction plaster

Straight answer

Is Calcium Sulfate safe for dogs?

Read the full diet, not this mineral

Calcium sulfate among the mineral names is an ordinary recipe adjustment. Its position cannot tell you the food's calcium and phosphorus levels. Check the nutritional adequacy statement for your dog's life stage. If you feed a growing dog and need the mineral figures, ask the maker for both.

Why it is in the food
Calcium without phosphorus

Our read // In our catalog

In 1 of every 32 foods we track

Share of foods that list it

3%

101 of the 3,204 foods with an ingredient list on file, from 16 brands. 59 dry dog food, 42 wet dog food.

Each square is 1% of the catalog

Where it sits on the label

Median position 14. In the top five of 1 food, so it is usually a minor ingredient.

Top five List position, heaviest first

Above the salt

52%

Listed before the salt in 52% of foods. In the rest it is under about 1% of the recipe.

Price per lb

Foods with it $3.91
All foods $3.25

Median of the cheapest bag price across 49 priced foods, 20% above the catalog. The price is the food's, not the ingredient's.

Who leans on it

26%

of the foods that list it are from Royal Canin. 16 brands use it in total.

What it is

How it is made

Gypsum is mined for large construction and farming markets. One feed-grade producer reports making its mineral ingredient from high-purity mined rock by fine grinding. This is a mined mineral, not a food-processing leftover.6,7,8

  1. 01 // Source Mined gypsum A documented feed-grade plant starts with high-purity gypsum rock, the hydrated form of calcium sulfate.
  2. 02 // Process Fine grinding The producer grinds the rock finely; its other listed processing options include air classification and heat treatment.
  3. 03 // Output Feed-grade powder Calcium sulfate leaves as a dry mineral ingredient offered in different grinds for animal rations.

What is in it

Composition, dry matter

29

% calcium

The anhydrous reference value. Feed-grade gypsum contains crystal water, so its calcium share as sold is lower.

Calcium 290 g/kg3
Sulfur 236 g/kg3
Phosphorus 0 g/kg3
Ash 100%3
Crude protein 0%3

These dry matter rows describe the anhydrous form. One feed-grade gypsum specification reports 20% calcium and 16% sulfur as sold. Crystal water and mineral purity change how much each pound supplies.3,7

Why it is in the bag

A real calcium source, usually in small amounts

  1. Main nutrition
  2. Supporting nutrient
  3. Does a job
  4. Mostly filler

Makers add it to raise calcium without adding phosphorus, so they can set the food's mineral balance. In one adult-dog trial it was one of 3 calcium salts, supplying a small share of the calcium. It usually sits among the minerals low on the list, so it is likely a minor contributor, but the calcium it adds is real. It is not filler: it carries no calories or protein, only mineral.1,3

  1. 01

    Adjusts calcium balance

    It raises calcium without bringing phosphorus along. A formulator can use it alongside other mineral salts to set the finished food's calcium and phosphorus levels.1,3

  2. 02

    Keeps powders flowing

    FDA lists anticaking as a technical food use for calcium sulfate. That supports a possible processing job, though an ingredient list cannot reveal its purpose in a particular kibble.5

  3. 03

    Draws on mineral supply

    Gypsum already serves large wallboard and farming markets, with mining and grinding infrastructure in place. Feed-grade material still needs suitable purity and handling; public sources give no pet-food price comparison.6,8

How much In a 40-week adult-dog trial, calcium sulfate supplied 6% of the test diet's calcium; the recipe percentage was not reported.1

Our read // The claims

What the evidence supports

Strong: controlled studies in dogs agree. Some: small or mixed dog data. Thin: mechanism or lab work only. None: nothing, or the evidence points the other way.

  1. Brands say

    Calcium sulfate raises calcium without adding phosphorus

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    The anhydrous feed table lists 290 g/kg calcium and 0 phosphorus. That makes it useful for adjusting mineral balance, but the ingredient alone says nothing about the finished food's calcium-to-phosphorus ratio.3

  2. Brands say

    Calcium sulfate is safe in formulated adult dog food

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    In one industry-funded trial, 10 of 18 adult beagles ate a high-calcium test diet for 40 weeks with no measured skeletal, urinary or kidney harm. Calcium sulfate supplied only 6% of that diet's calcium, so the trial cannot isolate this salt's effects.1,4

  3. Brands say

    Calcium sulfate stops mineral premixes from caking

    Outruns the evidence

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    FDA lists anticaking as a technical use in food. The adult-dog trial measured health, not premix flow, and an ingredient list gives no processing role. Its effect in a particular dog food is untested.1,5

  4. Owners say

    Extra calcium sulfate makes growing puppies' bones stronger

    Outruns the evidence

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    A review of growing-dog trials found that in most clinical trials, excess calcium was tied to altered skeletal development. The author proposes low phosphorus as a possible, unproven aggravating factor. The 40-week calcium sulfate trial involved only adult dogs.1,2

Straight answers

What owners ask

  1. Q01

    Is it just filler?

    No

    It supplies calcium, which a complete recipe must balance with phosphorus. It contributes no protein or calories. Its value depends on the finished mineral levels, not how appealing its name sounds.3,9

  2. Q02

    Is gypsum the same thing?

    The mineral, yes

    Gypsum is calcium sulfate with water held in its crystal structure. Feed-grade gypsum is prepared for animal food. Construction plaster is a different product and is not a dog supplement.6,7

  3. Q03

    Does it add phosphorus?

    No

    The feed table lists no phosphorus in calcium sulfate. That lets a maker add calcium without adding a phosphate salt. The whole recipe, rather than this ingredient, determines the final balance.1,3

  4. Q04

    Should I supplement my puppy?

    Usually no

    Do not add calcium sulfate to a complete growth diet on your own. A review of growing-dog trials found excess calcium tied to skeletal problems in most trials, with low phosphorus proposed as an unproven aggravating factor.2,9

Who uses it

Brands, best sellers and the company it keeps

Top brands, by foods that list it

  1. Royal Canin 26 / 160
  2. Fromm 18 / 67
  3. Kibbles n Bits 10 / 11
  4. Halo 9 / 41
  5. Now Fresh 8 / 35
  6. Stella & Chewy's 6 / 85
  7. Blue 6 / 186
  8. Hill's 4 / 116
  9. Simply Nourish 3 / 44
  10. Bil-Jac 3 / 32

Foods that list it / all the brand's recipes we track.

Plus 6 more brands.

Amazon best sellers that list it

  1. #55 Kibbles n Bits Small Breed Mini Bits Savory Beef & Chicken Flavors Dry Dog Food
  2. #59 Kibbles n Bits Original Savory Beef & Chicken Flavors Dry Dog Food

Rank on Amazon's dog food best seller list, checked October 2026.

Usually listed with, share of the foods that list it

  1. Natural Flavor 41%
  2. Chicken 38%
  3. Chicken Fat 36%
  4. Brown Rice 28%
  5. Chicken Broth 26%
  6. Brewers Rice 24%
  7. Tapioca 22%
  8. Salt 22%
  9. Corn 22%
  10. Carrots 21%
  11. Mixed Tocopherols 19%
  12. Wheat Gluten 19%

On the shelf

Foods that list Calcium Sulfate

101 foods in our catalog list it. These 60 list it highest on the label.

Now Fresh Chicken & Broth Wet Food for Small Breed Dogs Grain-Free Wet Dog FoodNow FreshNow Fresh Chicken & Broth Wet Food for Small Breed Dogs Grain-Free Wet Dog FoodWet // No. 5 on the labelBil-Jac Picky No More Pâté with Chicken & Chicken Liver Wet Dog FoodBil-JacBil-Jac Picky No More Pâté with Chicken & Chicken Liver Wet Dog FoodWet // No. 6 on the labelNow Fresh Good Gravy Beef Minced Grain-Free Wet Dog FoodNow FreshNow Fresh Good Gravy Beef Minced Grain-Free Wet Dog FoodWet // No. 6 on the labelStella & Chewy’s Gourmet Pate Gourmet Pâté for Dogs with Chicken & Chicken Liver - Grain Free Rich in Protein with Smooth Texture Wet Dog FoodStella & Chewy'sStella & Chewy’s Gourmet Pate Gourmet Pâté for Dogs with Chicken & Chicken Liver - Grain Free Rich in Protein with Smooth Texture Wet Dog FoodWet // No. 7 on the labelNatural Balance Platefulls Harvest Chicken & Rice Recipe Wet Dog FoodNatural BalanceNatural Balance Platefulls Harvest Chicken & Rice Recipe Wet Dog FoodWet // No. 8 on the labelRoyal Canin Veterinary Hydrolyzed Protein Small Dog Dry Dog FoodRoyal CaninRoyal Canin Veterinary Hydrolyzed Protein Small Dog Dry Dog FoodDry // No. 8 on the labelBil-Jac Pate Platters Pâté Platters with Chicken & Vegetables Grain-Free Wet Dog FoodBil-JacBil-Jac Pate Platters Pâté Platters with Chicken & Vegetables Grain-Free Wet Dog FoodWet // No. 9 on the labelSimply Nourish Skin & Coat Recipe Adult Wet Dog FoodSimply NourishSimply Nourish Skin & Coat Recipe Adult Wet Dog FoodWet // No. 9 on the labelSimply Nourish Gut Health Recipe Adult Wet Dog FoodSimply NourishSimply Nourish Gut Health Recipe Adult Wet Dog FoodWet // No. 9 on the labelBlue Wilderness Wild Meals Chicken & Sweet Potato Wet Dog FoodBlueBlue Wilderness Wild Meals Chicken & Sweet Potato Wet Dog FoodWet // No. 9 on the labelRoyal Canin Veterinary Hydrolyzed Protein Moderate Calorie Dry Dog FoodRoyal CaninRoyal Canin Veterinary Hydrolyzed Protein Moderate Calorie Dry Dog FoodDry // No. 9 on the labelTruDog Elevate Kettle Cooked Chunky Healthy Grains Chicken Stew w/ Carrots, P Wet Dog FoodTruDogTruDog Elevate Kettle Cooked Chunky Healthy Grains Chicken Stew w/ Carrots, P Wet Dog FoodWet // No. 10 on the label
Show 48 more
Now Fresh All Ages Breeds Beef & Rice Ground with Grains Wet Dog FoodNow FreshNow Fresh All Ages Breeds Beef & Rice Ground with Grains Wet Dog FoodWet // No. 6 on the labelNow Fresh Good Gravy Cage Free Chicken Recipe Wet Dog FoodNow FreshNow Fresh Good Gravy Cage Free Chicken Recipe Wet Dog FoodWet // No. 8 on the labelNow Fresh Good Gravy Chicken with Grains Wet Dog FoodNow FreshNow Fresh Good Gravy Chicken with Grains Wet Dog FoodWet // No. 8 on the labelNow Fresh Good Gravy Beef & Lamb Grain-Free Wet Dog FoodNow FreshNow Fresh Good Gravy Beef & Lamb Grain-Free Wet Dog FoodWet // No. 8 on the labelNow Fresh Chicken & Salmon Pâté Food for Senior Dogs Grain-Free Wet Dog FoodNow FreshNow Fresh Chicken & Salmon Pâté Food for Senior Dogs Grain-Free Wet Dog FoodWet // No. 9 on the labelRoyal Canin Veterinary Urinary SO + Hydrolyzed Protein Dry Dog FoodRoyal CaninRoyal Canin Veterinary Urinary SO + Hydrolyzed Protein Dry Dog FoodDry // No. 9 on the labelStella & Chewy’s Gourmet Pate Gourmet Pâté for Puppies with Chicken & Salmon - Grain Free Rich in Protein with Smooth Texture Wet Dog FoodStella & Chewy'sStella & Chewy’s Gourmet Pate Gourmet Pâté for Puppies with Chicken & Salmon - Grain Free Rich in Protein with Smooth Texture Wet Dog FoodWet // No. 10 on the labelHalo Elevate Kettle Cooked Chunky Healthy Grains Chicken Stew w/ Carrots, P Wet Dog FoodHaloHalo Elevate Kettle Cooked Chunky Healthy Grains Chicken Stew w/ Carrots, P Wet Dog FoodWet // No. 10 on the labelNow Fresh Good Gravy Chicken & Salmon Minced Grain-Free Wet Dog FoodNow FreshNow Fresh Good Gravy Chicken & Salmon Minced Grain-Free Wet Dog FoodWet // No. 10 on the labelSimply Nourish Hip & Joint Recipe Wet Dog FoodSimply NourishSimply Nourish Hip & Joint Recipe Wet Dog FoodWet // No. 10 on the labelBlue Natural Veterinary Diet WU Wet Dog FoodBlueBlue Natural Veterinary Diet WU Wet Dog FoodWet // No. 10 on the labelTruDog Elevate Kettle Cooked Chunky Healthy Grains Chicken & Salmon Stew w/ C Wet Dog FoodTruDogTruDog Elevate Kettle Cooked Chunky Healthy Grains Chicken & Salmon Stew w/ C Wet Dog FoodWet // No. 11 on the labelAgainst the Grain Pulled Beef with Gravy Dinner Wet Dog FoodAgainst the GrainAgainst the Grain Pulled Beef with Gravy Dinner Wet Dog FoodWet // No. 11 on the labelAgainst the Grain Pulled Chicken with Gravy Dinner Wet Dog FoodAgainst the GrainAgainst the Grain Pulled Chicken with Gravy Dinner Wet Dog FoodWet // No. 11 on the labelHalo Elevate Kettle Cooked Chunky Healthy Grains Chicken & Salmon Stew w/ C Wet Dog FoodHaloHalo Elevate Kettle Cooked Chunky Healthy Grains Chicken & Salmon Stew w/ C Wet Dog FoodWet // No. 11 on the labelFromm Four-Star Pâté Beef & Sweet Potato Pâté Grain-Free Wet Dog FoodFrommFromm Four-Star Pâté Beef & Sweet Potato Pâté Grain-Free Wet Dog FoodWet // No. 11 on the labelFromm Four-Star Pâté Duck À La Veg Pâté Wet Dog FoodFrommFromm Four-Star Pâté Duck À La Veg Pâté Wet Dog FoodWet // No. 11 on the label4health Stews Chicken Vegetable Stew For Dogs Wet Dog Food4health4health Stews Chicken Vegetable Stew For Dogs Wet Dog FoodWet // No. 11 on the labelBil-Jac Pate Platters Pâté Platters with Beef & Sweet Potatoes Grain-Free Wet Dog FoodBil-JacBil-Jac Pate Platters Pâté Platters with Beef & Sweet Potatoes Grain-Free Wet Dog FoodWet // No. 11 on the labelFromm Pâté Lamb & Sweet Potato Pâté Wet Dog FoodFrommFromm Pâté Lamb & Sweet Potato Pâté Wet Dog FoodWet // No. 11 on the labelRoyal Canin Poodle 8+ Adult Dry Dog FoodRoyal CaninRoyal Canin Poodle 8+ Adult Dry Dog FoodDry // No. 11 on the labelStella & Chewy’s Wild Red : Whole Prey Chicken & Lamb Recipe, Protein Rich, Grain Free & Legume Free Stew Wet Dog FoodStella & Chewy'sStella & Chewy’s Wild Red : Whole Prey Chicken & Lamb Recipe, Protein Rich, Grain Free & Legume Free Stew Wet Dog FoodWet // No. 12 on the labelStella & Chewy’s Wild Red : Whole Prey Chicken & Beef Recipe, Protein Rich, Grain Free & Legume Free Stew Wet Dog FoodStella & Chewy'sStella & Chewy’s Wild Red : Whole Prey Chicken & Beef Recipe, Protein Rich, Grain Free & Legume Free Stew Wet Dog FoodWet // No. 12 on the labelHealth Extension Digestive Support, Chicken & Pumpkin Entrée in Gravy Wet Dog FoodHealth ExtensionHealth Extension Digestive Support, Chicken & Pumpkin Entrée in Gravy Wet Dog FoodWet // No. 12 on the labelRoyal Canin Veterinary Health Nutrition Canine Advanced Mobility Support loaf in sauce Wet Dog FoodRoyal CaninRoyal Canin Veterinary Health Nutrition Canine Advanced Mobility Support loaf in sauce Wet Dog FoodWet // No. 12 on the labelRoyal Canin Veterinary Urinary SO Dry Dog FoodRoyal CaninRoyal Canin Veterinary Urinary SO Dry Dog FoodDry // No. 12 on the labelRoyal Canin Veterinary Urinary SO Small Dog Dry Dog FoodRoyal CaninRoyal Canin Veterinary Urinary SO Small Dog Dry Dog FoodDry // No. 12 on the labelRoyal Canin Veterinary Calm Dry Dog FoodRoyal CaninRoyal Canin Veterinary Calm Dry Dog FoodDry // No. 12 on the labelRoyal Canin Poodle Adult Dry Dog FoodRoyal CaninRoyal Canin Poodle Adult Dry Dog FoodDry // No. 12 on the labelRoyal Canin Cocker Spaniel Adult Dry Dog FoodRoyal CaninRoyal Canin Cocker Spaniel Adult Dry Dog FoodDry // No. 12 on the labelStella & Chewy’s Wild Red : Whole Prey Chicken & Turkey Recipe, Protein Rich, Grain Free & Legume Free Stew Wet Dog FoodStella & Chewy'sStella & Chewy’s Wild Red : Whole Prey Chicken & Turkey Recipe, Protein Rich, Grain Free & Legume Free Stew Wet Dog FoodWet // No. 13 on the labelHalo Elevate Dog Kettle Cooked Chunky Healthy Grains Duck and Beef Stew with Carrots, White Potatoes, and Brown Rice Can Wet Dog FoodHaloHalo Elevate Dog Kettle Cooked Chunky Healthy Grains Duck and Beef Stew with Carrots, White Potatoes, and Brown Rice Can Wet Dog FoodWet // No. 13 on the labelRoyal Canin Veterinary Vegetarian Dry Dog FoodRoyal CaninRoyal Canin Veterinary Vegetarian Dry Dog FoodDry // No. 13 on the labelRoyal Canin Veterinary Urinary SO Aging 7+ Dry Dog FoodRoyal CaninRoyal Canin Veterinary Urinary SO Aging 7+ Dry Dog FoodDry // No. 13 on the labelRoyal Canin Miniature Schnauzer Adult Dry Dog FoodRoyal CaninRoyal Canin Miniature Schnauzer Adult Dry Dog FoodDry // No. 13 on the labelRoyal Canin X-Small Adult Dry Dog FoodRoyal CaninRoyal Canin X-Small Adult Dry Dog FoodDry // No. 13 on the labelHalo Puppy Holistic Chicken & Chicken Liver Recipe Dry Dog FoodHaloHalo Puppy Holistic Chicken & Chicken Liver Recipe Dry Dog FoodDry // No. 13 on the labelHalo Adult Dog Holistic Chicken & Chicken Liver Recipe Dry Dog FoodHaloHalo Adult Dog Holistic Chicken & Chicken Liver Recipe Dry Dog FoodDry // No. 13 on the labelBlue Natural Veterinary Diet GI Low Fat Wet Dog FoodBlueBlue Natural Veterinary Diet GI Low Fat Wet Dog FoodWet // No. 14 on the labelRoyal Canin Veterinary Urinary SO Moderate Calorie Dry Dog FoodRoyal CaninRoyal Canin Veterinary Urinary SO Moderate Calorie Dry Dog FoodDry // No. 14 on the labelHill’s Prescription Diet c/d Multicare Urinary Care Chicken Flavor Dry Dog FoodHill'sHill’s Prescription Diet c/d Multicare Urinary Care Chicken Flavor Dry Dog FoodDry // No. 14 on the labelRoyal Canin X-Small Adult 8+ Dry Dog FoodRoyal CaninRoyal Canin X-Small Adult 8+ Dry Dog FoodDry // No. 14 on the labelRoyal Canin Small Indoor Senior Dry Dog FoodRoyal CaninRoyal Canin Small Indoor Senior Dry Dog FoodDry // No. 14 on the labelRoyal Canin Small Aging 12+ Dry Dog FoodRoyal CaninRoyal Canin Small Aging 12+ Dry Dog FoodDry // No. 14 on the labelFromm Classic Adult Whitefish & Rice Recipe Dry Dog FoodFrommFromm Classic Adult Whitefish & Rice Recipe Dry Dog FoodDry // No. 15 on the labelRoyal Canin Veterinary Canine Urinary SO thin slices in gravy Wet Dog FoodRoyal CaninRoyal Canin Veterinary Canine Urinary SO thin slices in gravy Wet Dog FoodWet // No. 15 on the labelHill’s Science Diet Puppy Chicken & Rice Stew Wet Dog FoodHill'sHill’s Science Diet Puppy Chicken & Rice Stew Wet Dog FoodWet // No. 15 on the labelRoyal Canin X-Small Aging 12+ Dry Dog FoodRoyal CaninRoyal Canin X-Small Aging 12+ Dry Dog FoodDry // No. 15 on the label

Sources

What we read

Checked October 1, 2026.

  1. 1 No Observed Adverse Effects on Health Were Detected in Adult Beagle Dogs When Fed a High-Calcium Diet for 40 Weeks Animals, 2021 // Journal
  2. 2 Factors that modify the effect of excess calcium on skeletal development in puppies British Journal of Nutrition, 2011 // Journal
  3. 3 Calcium sulfate anhydrous INRA CIRAD AFZ Feed Tables, n.d. // Database
  4. 4 21 CFR 582.5230 Calcium sulfate Electronic Code of Federal Regulations, 2026 // Regulator
  5. 5 Substances Added to Food (formerly EAFUS): Calcium Sulfate U.S. Food and Drug Administration, 2026 // Government
  6. 6 2026 USG Feed Grade Survey Guide - Detroit USG, 2026 // Industry
  7. 7 USG Calcium Sulfate FEED Grade Gypsum Technical Specifications USG, 2025 // Industry
  8. 8 Gypsum Statistics and Information U.S. Geological Survey, n.d. // Government
  9. 9 Reading Labels AAFCO, n.d. // Regulator
An ingredient on its own tells you very little. What matters is how much of it there is and where it sits in the list. That is why we weigh the top five rather than reacting to any single name further down. Back to the wiki

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