SoapmakingToolbox Recipe builder
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Free soapmaking calculators — no app, no login

Set your mold once.
Every tool remembers it.

Lye, water, superfat, fragrance and cost per bar for any oil blend — from a recipe builder that cites the saponification value behind every number and saves your mold on your device.

Open the recipe builder Browse all calculators
  • Every SAP value cited
  • Checked against SoapCalc
  • Saved on your device, never ours
Your mold profile Free · no login
Mold shape
Length units
Weight units
Weigh out — of oils

Enter your mold size to see how much oil it takes.

Saved on this device only. Every calculator here will remember it. Odd shape? Use the full mold calculator.

  1. 1

    Measure your mold

    Length, width, height — the card above turns it into the oil weight you should weigh out.

  2. 2

    Build or paste a recipe

    Pick oils and percentages in the recipe builder. Lye and water come out sized to your mold.

  3. 3

    Print the sheet and make soap

    One page with every weight, the safety checklist and the math — no email, no signup.

The recipe builder

One screen from oils to a finished, printable recipe

Pick oils, set percentages, and get everything a batch needs in one view — the numbers most lye calculators make you hunt through five screens for.

  • Lye and water for NaOH, KOH or a dual-lye blend, at your superfat and lye concentration
  • Fragrance weight at your load, checked against IFRA limits
  • Oil-property bars — hardness, cleansing, conditioning, bubbly, creamy — computed from each oil's fatty acids, with the usual ranges shown
  • Cost per bar from your oil prices and your mold's bar count
  • A link that is the recipe — share it, bookmark it, paste it in a forum
  • A one-page print sheet with the safety checklist on it
Open the recipe builder →
Lye is caustic. Goggles and gloves every time, lye into water never water into lye, and check any recipe — ours included — against a second calculator before you pour. This site prints the safety checklist on every recipe sheet. Read lye safety, start to finish →

The toolbox

Every calculator, grouped the way you use them

Set your mold and superfat once — every tool reads the same profile. Tools marked soon are on the build list and not linked until they exist.

Start here Recipe Builder Pick oils, set percentages — lye, water, fragrance, cost per bar and oil-property bars in one view.

Soap

Lye math, water, superfat, mold sizing — the numbers you use every batch.

Lye Calculator NaOH or KOH for any oil blend, with superfat, lye concentration and the SAP source for every oil — the quick version of the recipe builder. Mold Volume Loaf, round, cavity or water-fill → batter volume → how much oil to weigh out, at your lye concentration. Batch Resizer Paste any recipe, scale it to your mold, a new oil weight or a factor — every line rescaled, lye included. Lye Concentration Converter Water : lye ratio ↔ lye concentration ↔ “water as % of oils” — all three conventions, explained. Superfat Adjuster Change the superfat on a finished recipe and get the new lye weight — or see what superfat you actually made when the scale read a few grams off. Fragrance Load — Soap Grams of fragrance or essential oil for your batch — % of oils, oz per lb or % of finished soap — checked against the supplier’s IFRA maximum the way IFRA means it. Liquid Soap Calculator KOH at real-world purity, water for the paste, and the dilution math from paste to bottles. Dual-Lye Calculator NaOH / KOH blends for shave soap and cream soap — split by share of saponification, with the weight ratio it works out to. Masterbatch Lye How much 50% (or any %) lye solution equals the dry lye a recipe calls for, the extra water to add, and how to mix the jug. Essential Oil Blend Split your batch’s essential oil by top, middle and base notes — grams and drops per oil, balance read back against 30/50/20. Citric Acid & Vinegar Lye Extra NaOH or KOH for citric acid, vinegar or lactic acid in a recipe, the sodium citrate or acetate it makes — and the superfat you actually get if you forget.

Selling

For the makers running a tiny business.

Soap Cost & Pricing Cost per bar with your time and overhead in it, profit after fees at your price, break-even, and how many bars cover a craft-fair table. Bar Count & Cut How many bars a loaf yields at your cut thickness, what each weighs before and after cure — and how much oil it takes to make N bars of a label weight.

Guides

The why behind the numbers

Short, honest guides paired with the calculators — what superfat and lye concentration actually do, and how to fix the batch that went wrong.

Lye safety, start to finish Gloves, goggles, ventilation, and what to actually do if it splashes — the page to read before your first batch. Superfat explained: what % and why Why 5% is the default, when 8% or 20% is right, and what superfat does to lather and shelf life. Soda ash: causes and fixes The white film, why it isn’t the lye-heavy soap you fear, and the three mechanisms behind every prevention tip.

All guides →

Math you can check

Every oil in the calculator carries its saponification value, the published range it sits in, and where it came from. Results are verified against SoapCalc and SoapmakingFriend on real recipes, and every page has a “show the math” breakdown.

Private by design

No accounts, no tracking dashboards. Your mold profile and saved recipes live in your browser and nowhere else — a recipe link holds the recipe, not your identity.

Honest recommendations

When a page suggests a product, it's the one the numbers justify — and we say so when the cheap option wins. Where a link earns us a commission we disclose it, and it never changes a calculation.