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.
Add surfactants (SLS, SLSA, cocamidopropyl betaine), polyols (glycerin, propylene glycol, PDO), and additives (sodium lactate, salt, oatmeal) — each with auto-calculated lye adjustments by acid value.
Set hardness, cleansing, conditioning, bubbly, creamy, and longevity targets and let the AI optimizer work toward them — even without a Pro plan you can see the target overlay on your charts.
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 | SMF | Bramble Berry | FormulaAlchemy | SoapCalc.pro |
|---|---|---|---|---|---|
| Core Lye Calculation | |||||
| NaOH / KOH support | ✓ | ✓ | ✓ | ✓ | ✓ |
| Dual lye (NaOH + KOH blend) | ✓ | ✓ | – | ✓ | ✓ |
| Adjustable lye purity | – | ✓ | – | ✓ | ✓ |
| Water as ratio / % / concentration | ✓ | ✓ | – | ✓ | ✓ |
| Custom SAP override per oil | – | Paid | – | Pro | Pro |
| Analysis & Visualisation | |||||
| Soap property scores | ✓ | ✓ | – | ✓ | ✓ |
| Fatty acid breakdown | ✓ | ✓ | – | ✓ | ✓ |
| Visual property graph with ranges | – | ✓ | – | ✓ | ✓ |
| Extra Calculators | |||||
| Mold / batch size calculator | – | ✓ | – | ✓ | ✓ |
| Fragrance dosage calculator | – | ✓ | – | ✓ | ✓ |
| Fluid substitution calculator | – | ✓ | – | ✓ | ✓ |
| Soap type & water setting presets | – | ✓ | – | ✓ | ✓ |
| Scale batch | ✓ | ✓ | ✓ | ✓ | ✓ |
| Surfactants, polyols & additives | – | – | – | ✓ | ✓ |
| Target soap properties overlay | – | – | – | ✓ | ✓ |
| Pro & Advanced | |||||
| Target soap properties | – | – | – | Pro | Pro |
| AI-Powered Recipe Optimizer | – | – | – | Pro | Pro |
| Save recipes / batch history | – | Paid | – | Pro | Pro |
| Batch comparison side-by-side | – | – | – | Pro | Pro |
| Download SOP / PDF export | – | – | – | Pro | Pro |
| Cost tracking per oil | – | Paid | – | Pro | Pro |
| Custom oil database | – | ✓ | – | ✓ | ✓ |
| Custom ingredient database (surfactants, polyols, additives) | – | – | – | Pro | Pro |
| Min/max % limits per oil & ingredient | – | – | – | Pro | Pro |
| Problem Solver — AIchemist formulation review | – | – | – | Pro | Pro |
| PDF SOP export (print-ready) | – | – | – | Pro | Pro |
| 2-hour online training session | – | – | – | Pro | Pro |
| Ongoing training & technical support | – | – | – | Pro | Pro |
| Platform | |||||
| Mobile-friendly | ✓ | ✓ | ✓ | ✓ | ✓ |
| Server-side calculation | – | – | – | ✓ | ✓ |
| Free tier available | ✓ | ✓ | ✓ | ✓ | ✓ |
Paid = separate paid plan required · Pro = SoapCalc.pro Pro plan
Expand each calculator for an honest verdict on what it does well and where it falls short.
SoapCalc 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.
FormulaAlchemy is part of a broader professional formulation platform — alongside an SPF calculator, HLB calculator, and INCI checker — which gives it a different character from soap-only tools. The 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 Pro tier adds batch history, PDF export, AI blend recommendations, and custom SAP values. 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.
Unlock custom formulas, saved batch history, PDF export, AI-Powered Recipe Optimizer, and more — choose the plan that fits your workflow.
Override the default saponification value for any oil with your own lab-tested number for maximum accuracy.
AI-assisted oil blend suggestions based on your target soap quality properties and desired superfat percentage.
Export a print-ready PDF standard operating procedure for any recipe — perfect for production batches.
Save, name, and revisit every calculation you've ever run. Never lose a successful formula again.
Compare any two saved recipes side-by-side — properties, oils, and lye amounts — in one view.
Add your own oils with full SAP values and fatty acid profiles — blends, infusions, anything you source locally.
Save your own surfactants, polyols, and additives with custom acid values, % solid, and min/max usage rates — applied in every future batch automatically.
Send your full batch to the AIchemist for an expert formulation review — diagnoses common issues like rancidity risk, lather problems, or imbalanced fatty acids.
The core calculator is always free. Starter unlocks more tools; Pro adds everything for a professional operation.
| Feature | Free 7-day trial |
Starter ৳299 / 30 days |
Pro ৳499 / 30 days |
|---|---|---|---|
| Core calculations (always free) | |||
| NaOH, KOH & dual-lye calculation | ✓ | ✓ | ✓ |
| 150+ oils & fats database | ✓ | ✓ | ✓ |
| Superfat, water ratio, lye purity | ✓ | ✓ | ✓ |
| Fatty acid profile & quality scores | ✓ | ✓ | ✓ |
| Mold volume calculator | ✓ | ✓ | ✓ |
| Fragrance & colorant dosage | ✓ | ✓ | ✓ |
| Water / fluid substitution | ✓ | ✓ | ✓ |
| Soap type & water setting presets | ✓ | ✓ | ✓ |
| Scale batch | ✓ | ✓ | ✓ |
| Surfactants, polyols & additives | ✓ | ✓ | ✓ |
| Target soap properties overlay | ✓ | ✓ | ✓ |
| Starter & Pro features | |||
| Quick preset recipes | — | ✓ | ✓ |
| Target soap properties | — | ✓ | ✓ |
| Custom SAP value override | — | ✓ | ✓ |
| AI-Powered Recipe Optimizer | — | 50 / day | ✓ Unlimited |
| PDF download | — | 50 / day | ✓ Unlimited |
| Save & name batch history | — | 50 batches | ✓ Unlimited |
| Custom oil database | — | 50 oils | ✓ Unlimited |
| Custom ingredient database (surfactants, polyols, additives) | — | 50 ingredients | ✓ Unlimited |
| Min/max % limits per oil & ingredient | — | ✓ | ✓ |
| 2-hour online training session | — | ✓ | ✓ |
| Pro-only features | |||
| PDF SOP export (print-ready) | — | — | 150 / month |
| Problem Solver — AIchemist formulation review | — | 50 / day | 150 / month |
| Side-by-side batch comparison | — | — | ✓ |
| Ongoing training & technical support | — | — | ✓ |
|
Start free — open calculator
No sign-up needed for free features · 7 free Pro days on registration
|
See pricing → | See pricing → | |
Every new account gets 7 free Pro days automatically — no card needed to start.
Click any plan to open a WhatsApp message with the order details pre-filled. your plan access is activated manually after payment confirmation. Contact us via Email or WhatsApp.