Wash Formula Calculator

Detergent dosing isn't a single number per pound of laundry — it scales with how dirty the load is and gets adjusted upward for conditions that reduce detergent's effectiveness. This calculator starts from a base ounces-per-pound rate keyed to soil level (0.5 oz/lb light, 0.75 oz/lb medium, 1.2 oz/lb heavy), then applies two multipliers on top: a hardness adjustment that adds up to 10% more detergent for every 5 grains-per-gallon of water hardness above a baseline of 5 gpg (hard water's dissolved minerals interfere with surfactants, so harder water needs more detergent to get the same cleaning), and a temperature adjustment that boosts dosing by 15-30% for wash temperatures below 100°F, since cold water slows detergent's chemical activity and needs more product to compensate. Water usage is a simple 2 gallons per pound of load weight, and cycle time steps up with soil level (30/40/55 minutes) to give heavier soil more mechanical and chemical contact time.

Bleach is the one output that isn't scaled continuously — it only appears at all for heavy soil (level 2) and is calculated as a whole number of cups per 50 pounds of load, rounded up, reflecting that bleach is typically added in discrete measured doses rather than a smooth per-pound rate. Fabric softener is a flat 1 ounce per 10 pounds regardless of soil level or water conditions. The main thing to get right on input is soil level, since it drives both the base detergent multiplier and the cycle time and is the single biggest lever in the whole formula — a load marked "heavy" when it's really "medium" will be measurably over-dosed and over-processed.