Cold Process Soap Calculator & Cure Tracker

Each oil has a saponification value that tells you how much sodium hydroxide it takes to turn that oil into soap. You multiply each oil's weight by its value, add the results, then reduce the total by your superfat percentage. Lye & Loaf does this arithmetic live as you type, using hand-checked values for more than 30 oils, so the lye amount is always current with the recipe on screen.

Superfat is the percentage of oils you deliberately leave unsaponified by using slightly less lye than the full amount. A typical cold-process bar uses around 5 percent, which makes the soap gentler and adds a safety margin against excess lye. In Lye & Loaf you set superfat with a slider and the lye amount adjusts instantly, with sane limits and clear warnings.

Sodium hydroxide (NaOH) makes hard bar soap, while potassium hydroxide (KOH) makes soft or liquid soap. The two have different saponification values, so a recipe computed for one cannot be poured with the other. Lye & Loaf carries both values for every oil in its library and recalculates the whole recipe when you switch.

Most cold-process soap needs four to six weeks of curing after the cut, and high-olive recipes like Castile can take several months. Curing lets water evaporate, which makes the bar harder, milder and longer-lasting. Lye & Loaf gives each batch its own countdown anchored to the real cut date, so you can track several batches at different stages.

A water discount means using less water than the default amount for dissolving the lye, which speeds up cure and can reduce warping and soda ash. Discounting too far makes the batter set fast and hard to work with. Lye & Loaf lets you set the water discount directly and warns you when a value falls outside sensible limits.

INS and iodine are shorthand scores derived from a recipe's fatty-acid profile: iodine indicates how soft or prone to spoilage a bar may be, while INS is a traditional overall balance number. Alongside them, hardness, cleansing, conditioning, bubbly and creamy describe how the finished bar should feel and lather. Lye & Loaf shows all seven for every recipe before you mix, so you can rebalance oils on paper instead of wasting a batch.

Yes — Lye & Loaf ships with 30+ hand-checked oils and also lets you add any oil that isn't in the library. You enter its saponification values and fatty-acid breakdown once, and it then behaves like a built-in oil in every recipe, including the quality preview. That covers unusual butters and exotic blends without waiting for a database update.

Yes. Commercial sodium hydroxide is rarely 100 percent pure, and if you calculate as if it were, your real superfat drifts higher than planned. Lye & Loaf lets you enter the purity from your supplier's label and folds it into the lye amount automatically.

Lye & Loaf has a unit toggle for grams, ounces, pounds and kilograms, and switching converts the entire recipe in place. You can build a recipe in percentages, then scale it to the exact batch weight your mold holds in whichever unit you prefer. Nothing needs to be re-entered.

Serious makers keep a record of every batch — the oils, the lye, the superfat and the dates — so a good bar can be repeated and a bad one diagnosed. Lye & Loaf stores each batch in the app and prints a recipe card with a code that links back to it, so the paper by your pot and the record on your phone always match.

No. Fresh cold-process soap still contains active lye and is not skin-safe until saponification completes and the bar has cured, typically for four to six weeks. Lye & Loaf's cure countdown helps you wait out the full period, and the app is clear about its limits: it does the arithmetic from the values you enter and makes no chemistry-safety promise beyond the math. Always wear protection and follow trusted cold-process guidance.

Lye & Loaf runs entirely on your device — the oil library, the lye math, the quality preview and the cure countdowns all work offline. Nothing about your recipes leaves your phone. That also means it keeps working in a workshop or garage with no signal.