Lathr: Soap Calculator

Lathr is a precise soap calculator and studio workspace for soapmakers. Get exact lye, water and oil amounts for every batch, see your bar's qualities before you pour, and keep your recipes, molds and scent blends ready to reuse. CALCULATE WITH CONFIDENCE - Bar soap (NaOH), liquid soap (KOH) or dual lye - Lye purity, superfat and water settings - Enter oils by percent or by weight, in grams, ounces or pounds - Size a batch by oil weight or by mold size - Bar qualities: hardness, cleansing, conditioning, bubbly, creamy, iodine and INS - Reference oil library with NaOH and KOH SAP values - Lye safety checklist built in FREE TOOLS - Full soap calculator, always free - Save up to 3 recipes, 3 molds, 3 scent blends and 3 custom oils LATHR PRO - ONE-TIME PURCHASE - Unlimited recipes, molds, scent blends and custom oils - Batch journal and cure log with weight tracking - Cure timers and reminders - Batch costing, per-bar pricing and margin tools - Inventory, shopping lists and supplier records - Available-oil yield: see what your stock can make - Branded PDF batch sheets and CSV exports No account needed. Purchases are tied to your Apple ID and can be restored from Settings. Always add lye to water, never water to lye. Wear goggles and gloves, and confirm SAP values with your supplier. Run every new recipe through a second calculator before your first batch.