SoapmakingToolbox Recipe builder
Recipe Builder Every batchSpecial soapsScent and additivesFix or swapSelling Guides Gear About

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 moldLength, width, height. The card above turns it into the oil to weigh out.
  2. 2 Build the recipePick oils and percentages. Lye and water come out sized to your mold.
  3. 3 Print it and make soapOne page: every weight, the safety checklist and the math.

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.

  • 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 →
Recipe for a 10 × 3.5 × 2.5 in loaf
Olive oil 35%
Coconut oil 30%
Palm oil 30%
Castor oil 5%
Lye (NaOH) 138 g
Water 279 g
Fragrance 29 g
Batch 1,402 g
hardness 45
cleansing 20
conditioning 51
bubbly 25
creamy 29

Real output from the builder’s engine: 956 g of oils for the loaf in the card above, 5% superfat, 33% lye solution, 3% fragrance. Shaded: the usual range.

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, by the job in hand

19 calculators and the recipe builder, all reading the same mold profile. Set it once in the card at the top.

Every batch

Lye, water, superfat and mold size: the numbers behind any bar.

Lye Calculator NaOH or KOH for any oil blend, every SAP value cited. Mold Volume Your mold’s size in, the oil to weigh out. Batch Resizer Scale any recipe to your mold, lye included. Superfat Adjuster New lye for a new superfat, or the one you made. Lye Concentration Converter Water : lye ratio ↔ concentration ↔ % of oils. Masterbatch Lye How much 50% solution equals the dry lye you need.

Special soaps

Liquid, shave, milk, salt and melt and pour, each with its own math.

Liquid Soap Calculator KOH at real purity, paste water, then dilution. Dual-Lye Calculator NaOH and KOH blends for shave and cream soap. Milk Soap Calculator Milk for water, and the superfat its fat adds. Salt Bar & Brine Soap Salt by % of oils, and how much brine really holds. Melt and Pour Calculator Base to fill your mold, by volume, plus fragrance.

Scent and additives

What goes in at trace, weighed instead of guessed.

Fragrance Load (Soap) Grams of fragrance, checked against the IFRA maximum. Essential Oil Blend Top, middle and base notes in grams and drops. Additive Usage Rates Teaspoons per pound to grams, every weight sourced. Citric Acid & Vinegar Lye The extra lye an acid needs, or the superfat if not.

Fix or swap

When the batch went wrong, or the oil ran out.

Oil Substitution Out of an oil? The closest swaps by fatty acids. Rebatch Calculator Rescue a lye-heavy or greasy batch, gram for gram.

Selling

For the makers running a tiny business.

Soap Cost & Pricing Cost per bar with your time in it, and a price that pays. Bar Count & Cut Bars per loaf, and each one’s weight after cure.

Guides

New to soapmaking? Start here.

Five short reads, about 39 minutes in all, in the order your first batch needs them. The ones you finish are ticked off, on this device.

  1. 1 Lye safety, start to finish 7 min read
  2. 2 Your first cold process batch, step by step 13 min read
  3. 3 Trace: light, medium, thick 8 min read
  4. 4 Gel phase: force it or prevent it 6 min read
  5. 5 How long soap needs to cure (and why) 5 min read

Something went wrong?

Pick what your soap looks like for the guide that explains it.

All 8 symptoms →
White powder on top A dusty film that rubs off Soda ash: causes and fixes
Orange freckles Spots that turn up weeks or months later Dreaded orange spots (DOS)
Holes or glassy veins Air bubbles, or crackled glycerin rivers Air bubbles and glycerin rivers
A dark circle in the middle Translucent center, pale rim: partial gel Gel phase: force it or prevent it

All 19 guides →

Gear

Buying equipment?

Comparisons built on the same numbers as the calculators, including when the cheap option is the right one.

All gear →

94 oils, every SAP value sourced

Math you can check

Every oil in the calculator carries its saponification value and where it came from; 41 of the 94 are also checked against a published literature range. The lye math is checked against reference recipes worked by hand with SoapCalc's formulas, and the calculators show their working with your own numbers in it.

0 accounts, logins or trackers

Private by design

Your mold profile and saved recipes live in your browser and nowhere else. A recipe link holds the recipe, not your identity.

0 paid placements

How we recommend gear

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.