Soap Cure Time Calculator

Cured = Days since making ÷ Target cure days × 100 — Curing is water leaving, not saponification. The reaction itself is usually finished within 24–48 hours, so the loaf is already soap at that point, but it is soft and short-lived because the water you mixed in is still there. Over four to six weeks that water evaporates, the bar hardens and the lather turns finer and longer-lasting. Against a 42-day target, day 14 is 33% with 28 days to go. The target is a marker, not a deadline — bars keep improving past 100%, and an olive-heavy castile is visibly better at two or three months, better still at six. To watch it properly, use a scale: weigh one bar, note it, and re-weigh every few days; when the weight stops falling the water is gone, typically 5–10% below where it started.

With Days since making 14d, Target cure days 42d, the answer is Cured 33%.

Enter Days since making, Target cure days. The result recalculates as you type, and an empty box counts as zero.

Changing only Days since making (d) moves the answer to Days since making (d) 7 → Cured (%) 17 and Days since making (d) 28 → Cured (%) 67. The table below lays out five steps.

Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.

This percentage counts days and knows nothing about your room. In a humid summer the weight is still dropping well past day 42; in dry winter air it finishes early. Stand the bars on edge with space between them on an airy shelf — stacked or boxed, the days pass while the water stays. Wrapping in film or plastic belongs after the cure, not during it. And a bar that is soft because the lye was short never hardens: curing fixes moisture, not a mis-weighed recipe.