Stain Removal Guide Calculator

The age factor uses log base 2 of half the stain's age in hours, scaled by 0.15, which means the biggest jump in difficulty happens early — a stain going from fresh to a few hours old gets noticeably harder to treat, but a stain going from one week old to two weeks old barely changes further. This reflects that most of a stain's bonding into fibers happens in the first hours, after which additional time adds diminishing extra difficulty.

Fabric sensitivity represents a constraint on treatment options rather than a property of the stain, so it's applied as a flat addition (0 for sturdy fabrics, 1.5 for moderate, 3 for delicate) on top of the stain-driven difficulty score, rather than multiplying it. A delicate fabric makes any stain harder to treat safely by the same fixed amount, because the limitation is really about what chemicals and agitation you're allowed to use, not about how the stain chemistry itself changes.

It starts from a temperature that matches the stain's chemistry — cold water (20°C) for protein-based stains like blood or egg, since heat sets protein into fibers permanently, and warmer water (50°C) for oil and grease, since heat helps dissolve fats. It then caps that stain-driven temperature at a fabric-specific maximum (60°C for sturdy fabrics, down to just 30°C for delicates), taking whichever of the two is lower so the fabric limit always wins if the stain chemistry would otherwise call for something hotter.

The size factor is based on log base 10 of the stain area divided by 10, scaled by 0.1, so going from a small stain to a much larger one adds only a modest amount of extra difficulty rather than scaling proportionally with area. This reflects that treatment method and solution concentration don't fundamentally change with stain size — you mainly need more time and solution volume to fully saturate a bigger stained area, not a different approach.