- Everything here is free and provided as information, not as a formulation or safety service.
- We work hard to get the lye right — and you should still check any recipe against a second calculator before you pour.
- Lye burns. Goggles, gloves, ventilation, lye into water. Those rules outrank anything a calculator prints.
- Your batch is your responsibility. We can't see your oils, your scale, or what you actually weighed.
- If you sell soap, these tools don't make it compliant. Labeling and safety assessment are separate jobs.
Who these terms are with
SoapmakingToolbox (soapmakingtoolbox.com) is operated by Hamilton Digital Media Limited, registered in England and Wales under number 15608219, registered office 13a Mill Lane, Wimborne, Dorset, BH21 1LN, United Kingdom. In these terms, "we" and "us" mean that company. By using the site, you're agreeing to what follows.
What this site is
A set of free calculators and guides for making soap: lye and water for a recipe, mold sizing, resizing, fragrance loads, dilution, cost and pricing. There is nothing to buy from us, no account to create, and no subscription. You can use the tools for soap you make at home or soap you make to sell, at no charge.
What we promise about the math — and what we don't
We take the numbers seriously, because they are the entire point of the site. Concretely: every oil carries a saponification value with its source named (SoapCalc oil list) and, where we are confident of it, the range of values published in the literature; all the calculators share one calculation engine, so no two pages can disagree about the same recipe; that engine is covered by an automated test suite, including a set of reference recipes checked against SoapCalc, which runs before every deployment; and every result has a "show the math" panel so you can follow the arithmetic yourself.
What we cannot do is see your batch. A calculator only knows what you typed into it, and the usual causes of a wrong lye weight are not our arithmetic. They are an oil that isn't quite the one you selected (76° coconut and fractionated coconut are different oils with very different SAP values), a scale that reads in whole grams when the recipe needs tenths, a batch measured by volume rather than weight, or an oil whose real saponification value sits at the edge of its published range rather than the middle. So we provide the math without a warranty that a given result is correct for your specific batch, and you remain responsible for checking a recipe before the lye goes in. If a result looks wrong, it might be — please tell us, and we will check it and say so publicly if we were wrong.
- Sodium and potassium hydroxide are caustic. They burn skin and eyes and can cause permanent injury. Goggles and gloves whenever lye is out, solid or dissolved.
- Add lye to water, never water to lye. The reverse can boil violently and erupt.
- Ventilate. Dissolving lye releases fumes and heat. Keep children and animals out of the room.
- Check every recipe against a second calculator — including recipes from this site — before you pour.
- Never use uncured or untested soap on skin. Cure it, then zap-test it. Lye-heavy soap goes back in the pot or in the bin.
- Running water, not vinegar, on skin. Vinegar is for surfaces; acid on a caustic burn makes heat.
This isn't professional advice
The site is general information, not tailored advice about your formulation, and using it doesn't create a professional relationship between us. It is not a cosmetic safety assessment, a toxicological opinion, a legal opinion, or medical advice. If lye contacts skin or eyes, rinse with running water and get medical help — do not consult a calculator. If someone has reacted badly to a soap you made, that is a question for a doctor.
The soap-quality figures the tools print — hardness, cleansing, conditioning, bubbly, creamy, iodine, INS — are relative indices computed from fatty-acid proportions, used for comparing one recipe with another. They are not measurements of a finished bar, not claims about what soap will do to skin, and not a basis for marketing claims.
If you sell what you make
The seller tools here work out costs, prices and margins. They do not make a product lawful to sell, and nothing on this site is a substitute for the obligations that come with selling a cosmetic product where you live. In the UK and EU that typically includes a Cosmetic Product Safety Report from a qualified assessor, responsible-person and notification duties, and labeling rules; in the US it includes FDA and FTC labeling requirements, which differ depending on whether your product is legally "soap" or a cosmetic. Those are separate jobs, and they are yours.
In particular: our fragrance calculator can compare your load with a maximum you enter from a supplier's IFRA certificate. It does not hold IFRA data, cannot tell you what the limit for your fragrance is, and is not an IFRA conformity check.
What stays your responsibility
- Weighing accurately, on a scale that resolves what the recipe needs.
- Confirming the oil you selected is the oil in front of you.
- Personal protective equipment, ventilation, and keeping people and animals clear.
- Checking any recipe against a second calculator before you make it.
- Curing, testing and labeling anything you give away or sell.
- Storing and disposing of lye according to local rules.
Links to other sites
We link out to suppliers, manufacturers and reference sources. Some of those are affiliate links; commission never changes a calculation, and the details are set out in full in our affiliate disclosure. We don't control other websites and aren't responsible for their content, their products, or their privacy practices — once you leave here, their terms apply.
Content and copyright
The writing, design, code, curation and calculator implementations on this site belong to us. You're welcome to use the tools freely, quote us with credit and a link, share recipe links, and print or save results — including the printable sheets, which exist precisely so you can. Please don't republish our articles wholesale, copy the calculators onto another site, or scrape the site automatically.
To be clear about what we are not claiming: saponification values, fatty-acid profiles, iodine and INS numbers are published reference data. They are facts about oils, nobody owns them, and we credit the source we used on the pages that rely on them. What is ours is the engine, the curation, the interface and the words.
Availability
We aim to keep the site up and current, but it's provided as-is. We may change, move or retire tools and articles, and we don't guarantee uninterrupted access. Your saved recipes live in your browser, not with us, so they survive anything that happens to this site — and vanish if you clear your browser. Keep a copy of anything you can't lose.
Liability
To the extent the law allows, we're not liable for loss or damage arising from your use of this site — including wasted ingredients, a ruined batch, damage to equipment or surfaces, or business losses from acting on a result without checking it.
Nothing in these terms limits or excludes our liability for death or personal injury caused by our negligence, for fraud or fraudulent misrepresentation, or for anything else that cannot lawfully be excluded. If you're a consumer, you keep every statutory right you have where you live, and nothing here takes them away.
Governing law
These terms are governed by the laws of England and Wales, and disputes fall to its courts. If you use the site as a consumer somewhere else, you keep the protection of any mandatory consumer law that applies where you live.
Changes
We may update these terms as the site grows. The date at the top of this page shows when they last changed materially, and continuing to use the site means the current version applies.
Contact
Questions about these terms, or anything else: the contact page. Something here that's factually wrong, or a number that doesn't match your own working, goes straight to [email protected].