A great cold-process soap is a balancing act between hard, cleansing oils and soft, conditioning ones. This calculator takes your oil percentages and predicts the bar’s hardness, cleansing, conditioning, bubbly and creamy lather, plus the INS and iodine values, so you can fine-tune the blend before you ever reach for the lye.
How it works
Each oil contributes a known fatty-acid-derived value to every quality. The recipe property is the percentage-weighted average across all oils:
property = Σ (oil_value × oil_percent) / Σ (oil_percent)For example, coconut oil contributes high cleansing and bubbly numbers but low conditioning, while olive oil is the opposite. Blending them shifts every property toward a weighted middle. INS combines saponification and iodine into a single hardness index, and the iodine value tracks how soft and prone to oxidation the bar will be.
How it works in practice
A classic balanced recipe — 50 percent olive, 25 percent coconut, 20 percent palm, 5 percent castor — lands inside the recommended range on most properties, giving a hard, gently cleansing, conditioning bar with reliable lather. Push coconut much higher and cleansing climbs out of range toward a drying bar; drop the hard oils and hardness falls so the bar dissolves quickly in the shower.
Tips and notes
Keep cleansing in the low-to-mid range for face and sensitive-skin bars, and keep castor at 5 percent or below to avoid a sticky bar. Soft, high-iodine oils like sunflower and canola boost conditioning but raise oxidation risk, so use them sparingly and cure the soap longer. This tool is a recipe-property estimator only — always run a dedicated lye calculation with your chosen superfat before mixing any batch.