The most accurate free lye calculator for cold process and hot process soap. Calculate NaOH, KOH, or dual-lye with fatty acid profiles, mold volume, fragrance dosage and visual soap quality scoring. No sign-up needed.
Each method has its own process, timeline, and skill level. Pick the one that fits your style.
Mix oils with lye water at low temperatures, pour into a mold, cure for 4–6 weeks. Full control over every ingredient in the bar. This is what most soap makers do, and what the SoapCalc calculator is built for.
Learn about cold process →Same recipe as cold process, but you cook the soap (usually in a crock pot) until saponification is complete. Usable in days, not weeks. Rustic aesthetic. Same lye calculations as CP.
Learn about hot process →Start with a pre-made soap base. Melt it, add fragrance and color, pour into a mold. Done in under an hour. Great for beginners, kids (supervised), and quick gifts.
Melt & pour tips →Add your oils, set superfat and water, and get exact lye amounts instantly. No sign-up needed.
Pick a starting point — you can adjust quantities after loading.
Pick a preset or set custom targets.
Add lye to water — never water to lye. Verify with a pH strip before use.
Calculate, visualize, and validate your formulas — no sign-in required for the core tools.
Switch between lye types mid-recipe. Dual-lye mode lets you split NaOH/KOH by percentage for semi-solid and liquid bars.
Enter water as a lye-to-water ratio or as a percentage of total oil weight — whichever your recipe uses.
Instant visualization of oleic, lauric, palmitic, stearic, and linoleic with recommended range bands for a balanced bar.
Rectangular or cylindrical molds. Fill percentage, unit toggle (g / oz), and multi-mold batch sizing.
Calculates fragrance load at your chosen percentage of oil weight. Includes a colorant estimator for accurate batches.
Replace distilled water with milk, tea, aloe, or any fluid — adjusts water weight automatically.
Scale any recipe up or down by target weight. Works in grams and ounces with one click.
Load classic formulas instantly — Palm-Free Bar, 100% Coconut, Bastille, Castile, and more.
Fully responsive — works perfectly on your phone in the kitchen or studio. No app download required.
Every calculation shows a full breakdown of soap quality properties — hardness, cleansing, conditioning, bubbly, creamy, longevity — each plotted against the ideal range for a balanced bar.
Open Full Calculator — FreeAn honest, side-by-side look at every major soap lye calculator — what each does well, where it falls short, and who it's actually built for.
| Feature | SoapCalc.net | SMF | Bramble Berry | SoapCalc.pro | FormulaAlchemy |
|---|---|---|---|---|---|
| NaOH / KOH support | ✓ | ✓ | ✓ | ✓ | ✓ |
| Dual lye (NaOH + KOH blend) | ✓ | ✓ | – | ✓ | ✓ |
| Adjustable lye purity | – | ✓ | – | ✓ | ✓ |
| Water as ratio / % / concentration | ✓ | ✓ | – | ✓ | ✓ |
| Soap property scores | ✓ | ✓ | – | ✓ | ✓ |
| Fatty acid breakdown | ✓ | ✓ | – | ✓ | ✓ |
| Visual property graph with ranges | – | ✓ | – | ✓ | ✓ |
| Custom SAP override per oil | – | Paid | – | Starter | Starter |
| AI-Powered Recipe Optimizer | – | – | – | Pro | Pro |
| Mold / batch size calculator | – | ✓ | – | ✓ | ✓ |
| Fragrance dosage calculator | – | ✓ | – | ✓ | ✓ |
| Fluid substitution calculator | – | ✓ | – | ✓ | ✓ |
| Save recipes / batch history | – | Paid | – | Starter | Starter |
| Batch comparison side-by-side | – | – | – | Starter | Starter |
| PDF export | – | – | – | Pro | Pro |
| Download with SOP | – | – | – | Pro | Pro |
| Cost tracking per oil | – | Paid | – | Starter | Starter |
| Custom oils (user-defined) | – | ✓ | – | Starter | Starter |
| Mobile-friendly | ✓ | ✓ | ✓ | ✓ | ✓ |
| Server-side calculation | – | – | – | ✓ | ✓ |
| Free tier available | ✓ | ✓ | ✓ | ✓ | ✓ |
Paid = separate paid plan required · Starter = available from Starter plan · Pro = Pro plan only
Expand each calculator for an honest verdict on what it does well and where it falls short.
SoapCalc.net launched in 2001 and effectively defined what a lye calculator is. The soap property display — hardness, cleansing, conditioning, bubbly, creamy, iodine, INS — that every other tool now replicates was pioneered here. It recently received a rebuild and is now mobile-friendly, addressing a long-standing frustration.
The honest limitation is reliability. There were outages in July 2025 and February 2026 with no communication to users. The team has since added a status page, but if you are running a production business, an unreliable calculator is a serious problem.
Feature-wise, SoapCalc does the core calculation well. What it does not do: save recipes, show a visual property graph, offer a fragrance calculator, support mold sizing, allow lye purity input, or support custom oils.
SoapmakingFriend is one of the most feature-complete calculators available and has built a genuine community around it. It offers a smart recipe builder with real-time calculations, mold calculator, fragrance and additive tracking, and recipe saving. You can browse public recipes shared by other soapers, copy and customise them, and get support from a forum.
The friction point is the paywall. The free plan allows saving only two recipes — which SMF itself effectively acknowledges is just for testing. Custom oils, inventory tracking, and full batch cost analysis all require the paid tier. Some users have reported app bugs with premium subscribers seeing upgrade prompts incorrectly.
The Bramble Berry calculator assumes 90% purity for KOH and 97% for NaOH — the purities commonly available to consumers. That tells you exactly who it's designed for: someone buying supplies from Bramble Berry and making their first few batches. It calculates lye and water correctly but does not show property scores, fatty acid profiles, a visual chart, or any advanced features. No saving, no custom oils, no mold calculator.
This is not a criticism — it is a deliberate design choice for their audience. Once you start adjusting recipes yourself, you will quickly outgrow it.
SoapCalc.pro lye calculator is genuinely feature-rich for a free tool: NaOH, KOH, and dual-lye blending with an adjustable split slider, adjustable lye purity for both lye types, all three water input methods, fatty acid breakdown with visual range bands, soap quality property scores, a mold volume calculator, fragrance and colorant dosage, fluid substitution, batch scaling, and a surfactant/additive section. The oil database covers 150+ oils and no account is needed for any core features.
The Starter tier ($2.99/mo) adds quick preset recipes, target soap properties, custom SAP override, PDF export, and up to 50 saved batches. The Pro tier ($4.99/mo) adds AI-Powered Recipe Optimizer, AIchemist formula review, Problem Solver diagnostics, Download with SOP, unlimited batches, custom oils, and ongoing training & support. As a newer platform, it has less community history than SoapmakingFriend, and the broader multi-tool focus means soap-specific depth in areas like masterbatching and community recipe sharing is not the priority.
Preset recipes, custom SAP, AI tools, batch history, PDF SOP export, and expert support — everything you need to run a professional soap operation.
Load a ready-made formula instantly — choose from classic bar soap, castile, bastille, shampoo bar, liquid soap, and more. Starter & Pro.
Set your desired soap quality scores (hardness, lather, conditioning) and let the optimizer work backwards to suggest an oil blend. Starter & Pro.
Override the database saponification value for any oil with your own lab-tested number for maximum batch accuracy. Starter & Pro.
AI-assisted oil blend suggestions based on your target soap quality properties, budget constraints, and per-oil min/max limits. Starter & Pro.
Download a clean PDF of your recipe and results — great for sharing, printing, or keeping a record of every batch. Starter & Pro.
Save and name every calculation. Compare any two saved recipes side-by-side — properties, oils, and lye amounts — in one view. Starter (50 batches) · Pro (unlimited).
Submit your finished formula to the AIchemist for an AI-powered review — catches imbalances, flags unusual ratios, and suggests refinements. Pro only · 150/mo.
Describe a batch defect — ricing, seizing, soda ash, soft bars — and get an AI diagnosis with likely causes and corrective steps. Pro only · 150/mo.
Export a print-ready PDF standard operating procedure alongside your recipe — full ingredient list, safety notes, and production steps. Pro only · 150/mo.
Starter includes a 2-hour guided online training session. Pro adds ongoing training and dedicated technical support for your soap business.
The core calculator is always free. Starter adds presets and batch history. Pro unlocks AI tools, SOP export, and unlimited everything.
| Feature | Free | Starter | Pro |
|---|---|---|---|
| Core calculations | |||
| NaOH, KOH & dual-lye calculation | ✓ | ✓ | ✓ |
| 150+ oils & fats database | ✓ | ✓ | ✓ |
| Superfat, water ratio, lye purity | ✓ | ✓ | ✓ |
| Fatty acid profile & quality scores | ✓ | ✓ | ✓ |
| Mold volume calculator | ✓ | ✓ | ✓ |
| Scale batch | ✓ | ✓ | ✓ |
| Soap type & water setting presets | ✓ | ✓ | ✓ |
| Starter features | |||
| Quick preset recipes | — | ✓ | ✓ |
| Target soap properties | — | ✓ | ✓ |
| Custom SAP value override | — | ✓ | ✓ |
| Saved batches (up to 50) | — | ✓ | ✓ Unlimited |
| Custom oils (up to 50) | — | ✓ | ✓ Unlimited |
| 2-hour online training session | — | ✓ | ✓ |
| Pro-only features | |||
| AIchemist recipe verifier (150/mo) | — | — | ✓ |
| Problem Solver / diagnostics (150/mo) | — | — | ✓ |
| PDF SOP export (150/mo) | — | — | ✓ |
| Ongoing training & technical support | — | — | ✓ |
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Start free — open calculator
No sign-up needed for free features · 7 free Pro days on registration
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Starter $2.99 → | Pro $4.99 → | |
Every new account gets 7 free days of Pro access automatically — no card needed to start.
Click any plan to open a WhatsApp message with the order details pre-filled. Pro access is activated manually after payment confirmation. Contact us via Email or WhatsApp.