乳液與乳霜

q.s.       = 100 − Σ(stated percentages)
massᵢ      = batch × percentᵢ ÷ 100

HLB_blend  = Σ(massᵢ × HLBᵢ) ÷ Σmassᵢ
f_high     = (HLB_required − HLB_low) ÷ (HLB_high − HLB_low)

• Cosmetic formulations are written as percentage w/w of the finished product, totalling 100 %. Batch quantities are the percentage scaled to the batch mass: massᵢ = batch × percentᵢ ÷ 100.
• The convention "q.s. ad 100" (quantum satis — as much as suffices) marks the ingredient, conventionally the water phase, that makes the formula up to 100 %. — Only one ingredient can be q.s.; two would leave the split between them undefined.
• Usage rates are the supplier’s, from the ingredient’s own technical data sheet, and the range is a property of that material rather than of this calculator. — A rate inside its range is not a safety assessment. Preservative efficacy depends on the whole formula’s pH, water activity and packaging, and only a challenge test demonstrates it.
• W. C. Griffin, "Classification of Surface-Active Agents by HLB", Journal of the Society of Cosmetic Chemists 1 (1949) 311–326; and "Calculation of HLB Values of Non-Ionic Surfactants", JSCC 5 (1954) 249–256. — Defined for non-ionic surfactants only. An ionic or polymeric emulsifier has no HLB in this sense.
• The HLB of a blend is the mass-weighted mean of its components’ HLB values: HLB_blend = Σ(wᵢ × HLBᵢ) ÷ Σwᵢ. This additivity is the property that makes blending to a target possible and is stated in Griffin (1954).
• The required HLB of an oil is determined experimentally and published in supplier and handbook tables; the required HLB of a mixed oil phase is the mass-weighted mean of the components’ values. — Published required-HLB values for the same oil differ between sources, often by a point or more, and depend on whether the emulsion is oil-in-water or water-in-oil. Treat a match as a starting formulation, not a specification.