Epsom Salt USP Grade (Magnesium Sulfate) — Bath & Foot Soak
- Regular Price
- $ 17.99
- Sale Price
- $ 17.99
- Regular Price
Sold Out
- Unit Price
- per
Greenway Biotech · Family-owned in California since 1989
Epsom Salt, USP Grade.
For bath soaks, foot soaks and body scrubs.
Pure USP-grade magnesium sulfate heptahydrate (MgSO₄·7H₂O) for relaxing bath soaks, foot soaks and body scrubs. Fine-grain, fast-dissolving, third-party tested, with no added fragrance, dye, or filler. Sourced and packaged in the USA.
Find your size → See how to use itShips from California · 90-day satisfaction guarantee · Lab documents below
USP
U.S. Pharmacopeia purity standard
~9.8%
Elemental magnesium by weight
~13%
Elemental sulfur by weight
35+yrs
Family-owned in California
01 / Choose your size
Right-sized for your routine.
Pick a bag for how often you soak. Each bag's label gives the amount per bath, and stored sealed, Epsom salt keeps indefinitely.
| Size | Good for |
|---|---|
| 1 lb | Trying it or a few foot soaks |
| 3 lb | Occasional baths |
| 5 lb | Weekly baths |
| 10 lb | Regular baths |
| 20 lb | Frequent baths or a shared household |
| 25 lb | Stocking up |
| 2 × 25 lb | The largest supply, in two bags |
| Product Type | USP-grade magnesium sulfate bath salt |
|---|---|
| Sizes | 1, 3, 5, 10, 20 and 25 lb bags, or two 25 lb bags |
| Key Ingredient | Magnesium Sulfate Heptahydrate (MgSO₄·7H₂O) |
| Source / Origin | Sourced within the United States; packaged in Madera, California |
| Grade / Purity | USP (United States Pharmacopeia) raw material, per the producer’s Certificate of Analysis |
| Ingredients | 100% magnesium sulfate heptahydrate — no added fragrances, dyes, fillers, or preservatives |
| Free From | No fragrance, no dye, no filler, no preservative; vegan |
| Grain Size | Fine-grain, fast-dissolving in warm water (no gritty residue) |
| Shelf Life | Indefinite when stored sealed in a cool, dry place |
| Safety | External use only; not intended for ingestion. See Safety section below for full guidance. |
02 / Ideal for
One mineral.
Four honest uses.
Epsom salt isn't a cure-all — it's a versatile, fragrance-free magnesium sulfate that fits naturally into bath and body routines. Here's where it earns its place.
Relaxing Bath Soaks
Two cups per standard 40-gallon bath, dissolved in warm water — popular for evening wind-down routines.
Foot Soaks
Half a cup in a foot basin for tired feet after a long day. Many customers pair this with a hand or face cleansing routine for a brief reset.
Post-Activity Recovery Soaks
A warm Epsom soak after exercise or yardwork — popular for evening recovery rituals. The warmth and the routine itself contribute as much as the mineral.
Beauty & Exfoliation Scrubs
Mix equal parts Epsom salt with olive, jojoba, or coconut oil for a DIY body scrub. The fine granules exfoliate while the oil moisturizes.
03 / Why Epsom salt
USP grade is the standard.
Everything else is hardware-store.
A lot of bagged Epsom salt is technical grade, made for de-icing and industrial use rather than the bathtub. USP grade is a different specification altogether.
USP
U.S. Pharmacopeia purity specification.
USP grade means the magnesium sulfate we repackage is made and tested by its producer to the same purity, identity, and contaminant-limit standards used for pharmaceutical excipients. Technical grades meet a much looser specification: fine for de-icing, not what you want dissolving against your skin.
🧪
Third-party batch testing.
Every batch is independently tested for purity and screened for heavy metals. We don't use the absolute "heavy metal free" language some brands do — what we can say honestly is that results consistently come back well below required limits. The current batch test report is available on request.
⚡
Fine-grain, fast-dissolving.
Our smaller grain size dissolves in warm water without stirring. Add it while the tub fills and it's gone by the time you step in — no gritty residue at the bottom and no clumps to break up. Many customers comment on the dissolution speed compared to the chunkier grains they used before.
0
Zero added fragrance, dye, or filler.
100% magnesium sulfate heptahydrate. No synthetic perfume, no colorant, no anti-caking agent. That clean base makes our Epsom salt compatible with sensitive skin.
CA
USA-sourced, California-packaged.
Magnesium sulfate sourced from within the United States, packaged at our family-owned Madera, California facility — registered with the FDA. Backed by our 90-day satisfaction guarantee on every bag.
04 / The science
Why magnesium sulfate,
and what USP grade means.
9.8% elemental Mg
Plus ~13% elemental sulfur — calculated below
Epsom salt is magnesium sulfate heptahydrate — formula MgSO₄·7H₂O, molecular weight 246.47 g/mol. Despite the name, it isn't a culinary salt. The "salt" describes the crystal structure: a magnesium cation paired with a sulfate anion, plus seven water molecules locked into the crystal lattice. First isolated from saline springs near Epsom, Surrey, England in the early 1600s — hence the name that stuck.
The elemental math: magnesium is 24.305 g/mol, so MgSO₄·7H₂O is 24.305 ÷ 246.47 = ~9.86% elemental magnesium by weight, plus ~13.0% sulfur. Per pound (453.6 g), that works out to ~44.7 g of elemental magnesium and ~59 g of elemental sulfur.
"USP grade" is shorthand for compliance with the United States Pharmacopeia monograph for magnesium sulfate — a specification covering purity, identity, contaminant limits, and consistent batch quality. It's the same purity standard used for pharmaceutical excipients. Technical-grade magnesium sulfate isn't tested to this specification and shouldn't be used in baths.
Key Ingredients
The ingredient list is short by design: one compound, no additives.
Magnesium Sulfate Heptahydrate (MgSO₄·7H₂O)
The complete formula. Contributes both magnesium (~9.8% by weight) and sulfate to the water when dissolved. White crystalline granules; highly water-soluble; non-flammable; biodegradable.
Allergen note: No common allergens. No fragrance, dye, filler, or preservative added. People with confirmed magnesium-sensitive skin or any open wound on the contact area should consult a healthcare provider before use.
Technical Snapshot
| Chemical Name | Magnesium Sulfate Heptahydrate |
|---|---|
| Chemical Formula | MgSO₄·7H₂O |
| Molecular Weight | 246.47 g/mol |
| Elemental Magnesium Content | ~9.86% (24.305 / 246.47) |
| Elemental Sulfur Content | ~13.0% |
| CAS Number | 10034-99-8 |
| Grade | USP (United States Pharmacopeia) |
| Purity | ≥99.5% MgSO₄·7H₂O per USP monograph |
| Source | United States |
| Appearance | White crystalline granules; odorless |
| Solubility | ~710 g/L in water at 20 °C; highly water-soluble |
| Standard Preparation | 2 cups (~400 g) per standard 40-gallon bath — see Band 7 |
| Typical Bath Use | 2 cups per standard bath; ½ cup per foot basin |
| Safe Containers | Glass, ceramic, food-grade plastic, stainless steel |
| Packaged At | Greenway Biotech facility, Madera, California |
| Testing | Third-party lab tested; heavy metal screened (results consistently well below required limits) |
What to Expect
First use: The salt dissolves quickly in warm tub water with no stirring. The bath feels silkier than plain tap water — a subtle but noticeable difference.
Weeks 1-2: If you bathe consistently, you'll settle into your preferred amount (most start at 2 cups; some prefer 1.5 or 3).
Long term: Many customers describe Epsom soaks as a reliable evening wind-down ritual — popular before bed two to three times a week. Use as a relaxation routine, not a treatment.
05 / How to use
Pick your method.
Get the amount.
Two primary use methods. For a custom amount based on your tub or basin, use the calculator in the next section.
Bath Soak
Quick answer: 2 cups (~400 g) per standard 40-gallon bath, dissolved in warm running water. Soak 20-30 minutes.
| Tub Size | Epsom Salt | Water Temp | Soak Time |
|---|---|---|---|
| Standard (~40 gal) | 2 cups (~400 g) | 98-102 °F | 20-30 min |
| Garden tub (60+ gal) | 3 cups (~600 g) | 98-102 °F | 20-30 min |
| Lighter starting amount | 1.5 cups (~300 g) | 98-102 °F | 15-20 min |
| Sitz bath (~6 in depth) | 1 cup (~200 g) | Comfortably warm | 15-20 min |
Tip: Add salt while the water is running for fastest dissolution. Essential oils don't mix with bathwater, so we don't recommend adding them to a bath or to bath salts.
Foot Soak
Quick answer: ½ cup (~100 g) per basin of warm water. Soak feet for 30-45 minutes.
- Fill a basin or foot spa with comfortably warm water — enough to cover your feet up to the ankles.
- Add ½ cup (~100 g) of Epsom salt and stir until dissolved.
- Soak feet for 30-45 minutes. Bring a book or a podcast.
- Pat feet thoroughly dry and apply moisturizer. Customers often follow with our Solene Foot Cream for additional foot care.
06 / Directions
Fill.
Dissolve.
Soak.
Three steps for a standard bath. Use the calculator on the right for a custom amount based on your tub or basin size.
-
01
Fill the tub with warm water
Aim for 98-102 °F (37-39 °C) — warmer than body temperature but comfortable for an extended soak. Test the water with your hand before you step in. If you have low blood pressure, are pregnant, or have any heart condition, check with your healthcare provider on water temperature.
-
02
Add the salt while water is running
Two cups (~400 g) for a standard 40-gallon tub. Pour it under the stream — the agitation dissolves the crystals as the tub fills. No stirring required with our fine-grain crystals. For a sitz bath, foot soak, or larger garden tub, use the calculator on the right to dial in the amount.
-
03
Soak 20-30 minutes
The first ten minutes are the warmth working through; the rest is for the routine.
-
04
Rinse, pat dry, moisturize
A quick fresh-water rinse afterward is optional but pleasant. Pat dry rather than rubbing — your skin will feel silkier than usual, and aggressive towel-drying undoes that. Apply moisturizer or body oil to finish.
For external use only. Discontinue use if irritation occurs.
07 / Compare
Three magnesium forms.
Three different jobs.
Magnesium sulfate, magnesium chloride, and other magnesium salts behave differently in water, on skin, and in the body. Pick by the job you want done.
| Feature | Format | Contains Sulfur | Best For |
|---|---|---|---|
| Epsom Salt (Magnesium Sulfate) (this product) | Fine-grain crystal, fast-dissolving | Yes (~13%) | Bath soaks, foot soaks, body scrubs |
| Magnesium Chloride Bath Flakes | Large flakes, very fast-dissolving | No | Bath soaks with a silky-water character; external use only |
| Magnesium Chloride USP | USP-grade powder/flakes | No | DIY magnesium oil; supplement-labeled oral use where applicable |
| Magnesium Oil Spray | Ready-to-use topical spray | No | Targeted topical magnesium without a bath |
08 / Decision
Is Epsom salt the right
magnesium for you?
Honest sorting — Epsom salt does some things very well and isn't the right pick for every routine.
A Great Fit If You
- Want a classic, fragrance-free base for relaxing bath and foot soaks
- Prefer USP-grade purity for what touches your skin
- Like an indefinitely shelf-stable product you can stock up on
- Enjoy DIY body scrubs (Epsom + carrier oil works well)
Consider Another Option If
- You want a silky-water bath experience without the sulfate — try Magnesium Chloride Bath Flakes
- You want targeted topical magnesium without filling a tub — try Magnesium Oil Spray
- You're looking for an oral-use magnesium product — see Magnesium Chloride USP (labeled for oral use)
- You want Epsom salt for plants, lawns or hydroponics — see Epsom Salt for Plants, which has the garden directions
- You have very dry or sensitive skin and find Epsom soaks drying — start with a smaller amount or limit soak time
09 / Build the routine
Epsom is the base.
These build the ritual.
Pair Epsom salt with these complementary products for evening wind-down baths, post-soak skincare, and foot care routines.
10 / Safety & handling
Read this before
you draw the bath.
Epsom salt is generally well-tolerated for external use. A few honest notes on PPE for bulk handling, storage, and what to do if something goes wrong.
- External use only: This product is intended for bath soaks, foot soaks and body scrubs, not for ingestion. The page contains no oral-use directions because this product is not labeled for dietary supplement use. Keep out of reach of children and pets.
- PPE for bulk handling: No special PPE for normal bath use. For bulk pouring, wear gloves to prevent minor skin drying from prolonged contact, and avoid inhaling dust — open the bag and pour in a ventilated area.
- Bath precautions: Test water temperature before stepping in (aim for 98-102 °F). If you have low blood pressure, are pregnant or nursing, have a heart condition, or take medications, consult your healthcare provider before extended hot soaking. Discontinue use if skin irritation occurs.
- Storage: Magnesium sulfate is hygroscopic — it absorbs moisture from the air, which can cause clumping. Store in a cool, dry place in the original resealable bag or another airtight container. Keep away from direct sunlight and heat sources. Indefinite shelf life when stored properly. Keep out of reach of children and pets.
- First aid: Eye contact — flush with clean water for 15 minutes; seek medical attention if irritation persists. Skin contact — rinse affected area with water; generally well-tolerated; discontinue if irritation occurs. Ingestion — do not induce vomiting; contact a healthcare provider or Poison Control (1-800-222-1222). Inhalation of dust — move to fresh air; seek medical attention if symptoms persist.
11 / FAQ
Common questions.
Honest answers.
If your question isn't here, contact our team at questions@greenwaybiotech.com.
How much Epsom salt should I use in a bath?
For a standard 40-gallon bathtub, use 2 cups (about 400 g) of Epsom salt. Add it while the water is running for best dissolution. For a larger garden tub (60+ gallons), use 3 cups. For a lighter soak, 1.5 cups works well. For a sitz bath, use 1 cup per 6 inches of water depth. Use the calculator in the directions section above to dial in any other volume.
How often can I take Epsom salt baths?
Many people enjoy Epsom salt soaks two to three times per week as part of an evening wind-down routine. There's no strict frequency limit for healthy adults using it externally. If you have any medical conditions, take medications, or are pregnant or nursing, check with your healthcare provider for personalized guidance.
Is this Epsom salt made in the USA?
Yes. Our magnesium sulfate is sourced from within the United States and packaged at our family-owned Madera, California facility — registered with the FDA. Every batch is third-party lab tested for purity and screened for heavy metals before it ships.
What does USP Grade actually mean?
USP Grade describes the raw material: the magnesium sulfate we buy meets the purity, identity, and contaminant-limit standards set by the United States Pharmacopeia, confirmed by the producer’s Certificate of Analysis, and we repackage it without changing it. It's the same specification used for pharmaceutical excipients. Technical-grade magnesium sulfate isn't tested to this specification: fine for de-icing, not what you want dissolving in your bath. USP Grade is a purity standard, not a use designation: it doesn't make a product automatically suitable for oral use.
Does Epsom salt expire?
No. Magnesium sulfate is a stable mineral compound with an indefinite shelf life. Store it in a cool, dry place in the resealable bag or another airtight container to prevent moisture absorption and clumping. It won't lose effectiveness over time even after years in storage.
What's the difference between Epsom salt and table salt?
Different compounds entirely. Epsom salt is magnesium sulfate (MgSO₄·7H₂O); table salt is sodium chloride (NaCl). Epsom contains magnesium and sulfur; table salt contains sodium and chlorine. The "salt" in both names refers to the crystal structure — a positively charged ion paired with a negatively charged one — not to the seasoning you put on food. They cannot be substituted for each other in any use case.
Can I add essential oils to my Epsom salt bath?
Not directly. Essential oils don't mix with water, so drops added to a bath float on the surface undiluted and can irritate skin, and bath salts, Epsom salt and milk don't disperse them. Enjoy essential oils in a diffuser instead.
Will Epsom salt clog my drain or harm my septic system?
No. Our fine-grain Epsom salt dissolves completely in bath water and is safe for standard plumbing and septic systems when used as directed. Magnesium sulfate is biodegradable and environmentally benign at normal bath-use concentrations — much lower environmental impact than fragranced or dyed bath products.
Can I use this Epsom salt in my garden?
For plants, lawns and hydroponics, use Epsom Salt for Plants. It is the same USP-grade magnesium sulfate, sold with garden and lawn directions. This listing covers bath and body use only.
Can I use Epsom salt if I have sensitive skin?
Our USP Grade Epsom salt is pure magnesium sulfate with no added fragrances, dyes, or preservatives — a cleaner option for sensitive skin than scented bath products. If you're new to Epsom soaks, start with a smaller amount (1 cup instead of 2) and a shorter soak time (15 minutes instead of 30) to see how your skin responds. Discontinue immediately if irritation occurs.
Can I take Epsom salt orally?
This product is labeled and sold for external use only: bath soaks, foot soaks and body scrubs. It does not carry dietary-supplement labeling, so we don't provide oral-use directions. Our Magnesium Chloride USP is labeled for oral use, as are our Magnesium Citrate and Magnesium Oxide powders. For ingestion-based use cases, talk to a healthcare provider.
How is the magnesium content calculated?
Magnesium sulfate heptahydrate has the formula MgSO₄·7H₂O and a molecular weight of 246.47 g/mol. Magnesium itself is 24.305 g/mol. So 24.305 ÷ 246.47 = ~9.86% elemental magnesium by weight. Per pound of Epsom salt (453.6 g), that's roughly 44.7 g of elemental magnesium and ~59 g of elemental sulfur (the other ~13%). The remainder is oxygen and the seven water molecules locked into the crystal.
Ready to start?
Pick your size. We'll ship it from California.
Sizes from a 1 lb bag up to two 25 lb bags, sourced and packaged in the USA. Free shipping on orders over $100 in the continental US, and our 90-day satisfaction guarantee if Epsom salt isn't right for your routine.
Choose your size →Ships from California · 90-day satisfaction guarantee · Lab documents above
C
Amazing quality epsom salt for a good price! Thank you guys for doing an amazing job!
A
Excellent value with fast free secure shipping
M
Well packaged product showed up amazingly fast. I attempted to contact greenway many times by email and by the website listed phone number. I received exactly one response from Tom Fert saying that they could help me establish a weekend pickup. It has now been a couple weeks and I still don't have a weekend pickup date, and complete radio silence about getting copies of the 3rd party testing results that they claim on their website.
I am greatly concerned about the quality of the product if the company is not really willing to provide the data that it claims to have, and advertises as a selling point of its products. I am also concerned about dealing with a business who can't or won't communicate.
I
Excellent with the purchase and customer service
J
Very pleasant for sure. Definitely will buy again
B
I DID NOT RECEIVE THIS ORDER! Contacted Greenway Biotech, Inc. numerous times!
J
IT GREAT..............................................................................................................
F
Best ever Epsom salts for my bath.
H
Used product in the past and was very good.
S
Will definitely continue to buy
B
I love your products, and your service.
And I appreciate that your company takes time to answer questions.
L
I really like the smoothness of the water when bathing in the Epsom salt water & my muscles feel so relaxed afterward. I would definitely buy this product again
F
Free shipping and high quality products are hard to find. Greenway biotech always pulls through.
P
Loved it. Let me know about specials
E
Have not received it yet
L
Amazing experience and great product
a
I love the Epsom salt! It's a great product.
R
Love putting this Epson Salt in the bath and relaxing. I feel like it really helps me unwind and helps with achy muscles. I also sprinkle some on my plants and it seems to help them grow healthier.
C
I use a cup daily to soak in the tub for my back pain. Will buy again.
R
Grear
F
Delivery is super swift. Packaging is attractive. Customer service is cordial, informed, and sometimes includes sweet handwritten notes. But the best part is the quality and quantity of Greenway Biotech's Epsom Salt. Having it available 25, 50, or 75 pounds at a times means I can use 2 cups per bath and enjoy my soaks. It helps my insomnia immeasurably. I've been buying my Epsom Salt from Greenway Biotech for years and hope to do so for years to come. I've recently re-started gardening so I'm looking to Greenway to help me supplement my soil organically with many of their other products. I literally can't say enough good things about Greenway -- and they're about the only company of any kind I feel that way about.
G
Awesome product and fast shipping
S
Great product. Was super impressed with shipping time. So happy I found this company!
E
Fast shipping :-) Quality products!
R
Very relaxing 😌
F
I have been buying Epsom Salt from Greenway Biotech for years. Greenway's product is the best ever. Its quality is exceeded only by the company's amazing customer service and its shockingly swift delivery. Greenway and its Epsom Salt have set a standard for years in all three areas that any other company of any kind has yet to meet. Plus this latest order had a significant paisley design on its label -- aesthetically pleasing and contributing to raising awareness of a vital issue.
F
I haven't used this item yet but Im always impressed with your product. free shipping and affordable price keeps me loyal to greenway biotech over chem grow. thank you
M
never received it.
J
Aloha! I certainly appreciate this company and the product that actually comes from the earth and NOT man made as most other Epsom salts. I use it in various ways, mostly in the garden to enhance my plants' nutrition. Thank you, (Mahalo) for this wonderful product! I will certainly buy/recommend! Keoni
M
I make bath bombs and bath salts to give to friends and this site is by far the best deal around. Also great to fertilize my plants!
T
Big quantity of 25lb is great for the bulk price. I will continue to buy. Unscented is nice, so I can add my own scent whenever I want.
D
Very pleased with the whole transaction. It was shipped quickly & carefully. I would like to purchase this again but would like it in a finer ground option. The large crystals take longer to dissolve but are still a good quality product.
